Title of Invention

MULTIPLE ELECTROSPRAY DEVICE, SYSTEMS AND METHODS

Abstract

A microchip-based electrospray device, system, and method of fabrication thereof are disclosed. The electrospray device includes a substrate defining a channel between an entrance orifice on an injection surface and an exit orifice on an ejection surface, a nozzle defined by a portion recessed from the ejection surface surrounding the exit orifice, and an electric field generating source for application of an electric potential to the substrate to optimize and generate an electrospray. A method and system are disclosed to generate multiple electrospray plumes from a single fluid stream that provides an ion intensity as measured by a mass spectrometer that is approximately proportional to the number of electrospray plumes formed for analytes contained within the fluid. A plurality of electrospray nozzle devices can be used in the form of an array of miniaturized nozzles for the purpose of generating multiple electrospray plumes from multiple nozzles for the same fluid stream. This invention dramatically increases the sensitivity of microchip electrospray devices compared to prior disclosed systems and methods.

Full Text

This application claims the benefit ofU.S. Provisional Patent Application Serial No. 60/173,674, filed December 30,1999, which is herein incorporated by reference in its entirety. FIELD OF THE INVENTION The present invention relates generally to an integrated miniaturized fluidic system fabricated using Micro-EIectroMechanicai System (MEMS) technology, particularly to an integrated monolithic microfabricated device capable of generating multiple sprays from a single fluid stream. BACKGROUND OF THE INVENTION New trends in drug discovery and development are creating new demands on analytical techniques. For example, combinatorial chemistry is often employed to discover new lead compounds, or to create variations of a lead weeks). Testing such a large number of compounds for biological activity in a timely and efScient manner requires high-throughput screening methods which allow rapid evaluation of the characteristics of each candidate compound. The quality of the combinatorial library and the compounds contained therein is usedjojssess the validity of the biological screening data. Confirmation that the correct molecular weight is identified for each compound or a statistically relevant number of compounds along with a measure of compoimd purity are two important measures of the quality of a combinatorial library. Compounds can be analytically characterized by removing a portion of solution from each well and injecting the contents into a separation device such as liquid chromatography or capillary electtophoresis instrument coupled to a mass spectrometer. Development of viable screening methods for these new targets will often depend on the availability of rapid separation and analysis techniques for analyzing the results of assays. For example, an assay for potential toxic metabolites of a candidate drug would need to identify both the candidate drug and the metabolites of that candidate. An understanding of how a new compound is absorbed in the body and how it is metabolized can enable prediction of the likelihood for an increased therapeutic effect or lack thereof. Given the enormous number of new compounds that are being generated daily, an improved system for identifying molecules of potential therapeutic value for drug discovery is also critically needed. Accordingly, there is a critical need for high-throughput screening and identification of compound-target reactions in order to identiiy potential drug candidates. Liquid chromatography (LC) is a well-established analytical method for separating components of a fluid for subsequent analysis and/or identification. Traditionally, liquid chromatography utilizes a separation column, such as a cylindrical tube with dimensions 4.6 myn inner diameter by 25 cm length, filled with tightly packed particles of 5 fim diameter. More recently, particles of 3 fim diameter are being used in shorter length columns. The small particle size provides a large surface area that can be modified with various chemistries creating a stationary phase. A liquid eluent is pumped through the LC column at an optimized flow rate based on the column dimensions and particle size. This liquid eluent is referred to as the mobile phase. A volume of sample is injected into the mobile phase prior to the LC column. The analytes in the sample interact with the stationary phase based on the partition coefficients for each of the analytes. The partition coefBcient is defined as Che ratio of the time an anaiyte spends interacting with the statioi^iry phase to the time spent interacting with the mobile phase. The longer an anaiyte interacts with the stationary phase, the higher the partition coefficient and the longer the anaiyte is retained on the LC column. The diffusion rate for an anaiyte through a mobile plmse [mobile-phase mass tramfer) also affects the partition coefficient. The mobile-phase mass transfer can be rate limiting in the performance of the separation column when it is greater than 2 um (Knox, I.H.J. ]. Chromatogr. Sci. 18:453^61 (19S0)). Increases in ciiromatographic separation are achieved when using a smaller particle size as the jtationary phase support. The purpose of the LC column is to separate analytes such that a imique response for each anaiyte from a chosen detector can be acquired for a ijuantitative or qualitative measurement. The ability of a LC column to generate a separation is determined by the dimensions of the column'and the particle size -. supporting the stationaiy phase. A measure of the abUity of LC columns to separate a given analyte is referred to as &e fteoretica] plate number N. The retention time of an analyte can be adjusted by varying the mobile phase composition and the partition , coefficient for an analyte. Experimentation and a fundamental understanding of the partition coefficient for a given analyte determine which stationaiy phase is chosen. To increase the throughput of LC analyses requires a reduction in the dimensions of the LC column and the stationary phase particle dimensions. Reducmg the length of the LC column from 25 cm to 5 cm will result in a factor of 5 decrease in the retention time for an analyte. At the same time, the tiieoretical plates are reduced 5-fold. To maintain the theoretical plates of a 25 cm length column packed with 5 nm particles, a 5 cm coliunn would need to be packed with 1 jim particles. However, the use of such small particles results in many technical challenges. One of these technical challenges is the backpressure resulting from pushing the mobile phase through each of these colunms. The backpressure is a measure of the pressure generated in a separation column due to pumping a mobile phase at a given flow rate through the LC column. For example, the typical backpressure of a 4.6 mm inner diameter by 25 cm length column packed with 5 |im particles generates a baclqjressure of 100 bar at a flow rate of 1.0 mL/min. A 5 cm column packed with 1 \im particles generates a back pressure 5 times greater than a 25 cm coltmm packed with 5 pjn particles. Most commerciaUy available LC pumps are limited to operating pressures less than 400 bar and thus using an LC column with these small particles is not feasible. Detection of analytes separated on an LC colunm has traditionally been accomplished by use of spectroscopic detectors. Spectcoscopic detectors rely on a change in refractive index, ultraviolet and/or visible light absorption, or fluorescence after excitation with a suitable wavelength to detect the separated components. Additionally, the effluent from an LC column may be nebulized to generate an aerosol which is sprayed into a chamber to measure the light scattering properties of the analytes eluting from the column. Alternatively, the separated components may be passed from the hquid chromatography column into other types of analytical instruments for analysis. The volume from the LC colimm to the detector is minimized in order to maintain the separation efficiency and analysis sensitivity. All system volume not directly resulting &om the separation column is referred to as the dead volume or extra-column volume. The miniaturization of liquid separation techniques to the nano-scale involves small column internal diameters ( Capillary electrophoresis is a technique that utilizes the electrophoretic nature of molecules and/or the electroosmotic flow of fluids iii small capillary tubes to separate components of a fluid. Typically, a fiised silica capillary of 100 pm inner diameter or less is filled with a buffer solution containing an electrolyte. Each end of the capillary is placed m a separate fluidic reservoir containing a buffer electrolyte. A potential voltage is placed in one of the buffer reservoirs and a second potential voltage is placed in the other buffer reservoir. Positively and negatively charged species will migrate in opposite directions through the capillary under the influence t.'f the electric field estabhshed by the two potential voltages applied to the buffer reservoirs. Electroosmotic flow is defined as the fluid flow along the walls of a capillary due to the migration of charged species fi'om the buffer solution imder the influence of the applied electric field. Some molecules exist as charged species when in solution and will migrate through the capillary based on the charge-to-mass ratio of the molecular species. This migration is defined as electrophoretic mobility. The electroosmotic flow and the electrophoretic mobility of each component of a fluid determine.the overall mieration for each flin'diV. rnmnnr.ent- Thft flTiid flnwnmfilp resulting &om electroosmotic flow is flat due to the reduction in frictional drag along the walls of the separation channel. This results in improved separation efficiency compared to liquid chromatography where the flow profile is parabolic resulting from pressure driven, flow. Capillary electrochromatography is a hybrid technique that utilizes the electrically driven flow characteristics of eiectrophoretic separation methods within capillary columns packed with a solid stationary phase typical of liquid chromatography. It couples the separation power of reversed-phase liquid chromatography with the high efQciencies of capillary electrophoresis. Higher efQciencies are obtainable for capillary electrochromatography separations over liquid chromatography, because the flow profile resulting from electroosmotic flow is flat due to the reduction in frictional drag along the walls of the separation chaimel when compared to the parabolic flow profile resulting from pressure driven flows. Furthermore, smaller particle sizes can be used in capillary electrochromatography than in liquid chromatography, because no backpressure is generated by electroosmotic flow. In contrast to electrophoresis, capillary electrochromatography is capable of separating neutral molecules due to analyte partitioning between the stationary and mobile ptmses of the column particles using a liquid chron^tography separation mechanism. Microchip-based separation devices have been developed for rapid analysis of large numbers of samples. Compared to other conventional separation devices, these microchip-based separation devices have higher sample throughput, reduced sample and reagent consumption, and reduced chemical waste. The liquid flow rates for microchip-based separation devices range from approximately 1-30O nanoliters per minute for most applications. Examples of microchip-based separation devices include those for capillary electrophoresis ("CE"), capillary electrochromatography C'CEC") and high-performance liquid chromatography ("HPLC") include Harrison et al.. Science 261:859-97 (1993); Jacobson et al., Anal. Chem. 66-.1114-18 (1994), Jacobson et al.. Anal. Chem. 66-.2369-73 (1994), Kutter et al.. Anal. Chem. 69:5165-71 (1997) and He et al.. Anal. Chem. 70:3790-97 (1998). Such separation devices are capable of fast analyses and provide improved precision and reliability compared to other conventional analytical instruments. ine work of He et al.. Anal. Chem. 70:3790-97 (1998) demonstrates some of the types of structures that can be fabricated in. a glass substrate. This work shows that co-located monolithic support structures (or posts) can be etched reproducibly in a glass substrate using reactive ion etching (RIE) techniques. Currentiy, anisotropic RIE techniques for glass substrates are limited to etching features that are 20 yjn or less in depth. This work shows rectangular 5 |im by 5 ^im width by 10 (im in depth posts and stated that deeper structures were difScuIt to achieve. The posts aie also separated by 1.5 pm.. The posts supports the stationary phase just as with the particles in LC and CEC columns. An advantage to the posts over conventional LC and CEC is that the stationary phase support sti:uctures are monolithic with the substrate and therefore, immobile. He et. al., also describes the importance of maintaining a constant cross-sectional area across the entire length of the separation channel. Large variations in the cross-sectionai area can create pressure drops in pressure driven flow systems. In electiokinetically driven flow systems, large variations in the cross-sectional area along the length of a separation channel can create flow restrictions that result in bubble foraiation in the separation channel. Since the fluid flowing through the separation channel fiinctions as the source and carrier of the mobile solvated ions, formation of a bubble in a separation channel will result in the disruption of the electroosmotic flow. Electrospray ionization provides for the atmospheric pressure ionization of a liquid sample. The electrospray process creates highly-charged ■ droplets that, under evaporation, create ions representative of the species contained in the solution. An ion-sampJing orifice of a mass spectrometer may be used to sample these gas phase ions for mass analysis. When a positive voltage is applied to the tip of the capillary relative to an extracting electrode, such as one provided at the ion-sampling orifice of a mass spectrometer, the electric field causes positively-charged ions in the fluid to migrate to the surface of the flitid at the tip of the capillary. When a negative voltage is applied to the tip of the capillary relative to an extracting electrode, such as one provided at the ion-sampling orifice to the mass spectrometer, the electric field causes negatively-charged ions in the fluid to migrate to the surface of the fluid at the tip of the capillary. When the repulsion force of the solvated ions exceeds the surface tension of the fluid being electrosprayed, a volume of the fluid is pulled into the shape of a cone, known as a Taylor cone, which extends from the tip of the capillary. A Hquidjet extends from the tip of the Taylor cone and becomes unstable and generates charged-dropiets. These small charged droplets are drawn toward the extracting electrode. The small droplets are highly-charged and solvent evaporation from the droplets results in the excess charge m the droplet residing on the analyte molecules m the electrosprayed fluid. The charged molecules or ions are drawn through the ion-sampling orifice of the mass spectrometer for mass analysis. This phenomenon has been described, for example, by Dole et al., Chem. Phvs. 49:2240 (1968) and Yamasbita et aL. J. Phvs. Chem. 88:4451 (1984). The potential voltage ("V") required to initiate an electrospray is dependent on the surface tension of the solution as described by, for example, Smith, IEEE Trans, hid. Anpl. 1986, IA-22:527-35 (1986). Typically, the electric field is on the order of approximately 10* V/m. The physical size of the capillary and the fluid surface tension determines the density of electric field lines necessary to initiate electrospray. When the repulsion force of the solvated ions is not sufficient to overcome the surface tension of the fluid exiting the tip of the capillary, large poorly charged droplets are formed. Fluid droplets are produced ■wten the electrical potential difference applied between a conductive or partly conductive fluid exiting a capillary and an elecfrode is not sufficient to overcome the fluid surface tension to form a Taylor cone. Electrospray Ionization Mass Spectrometry: Fundamentals, Instrumentation, and Applications^ edited by R,B. Cole, ISBN 0-471-14564-5, John Wiley & Sons, Inc., New York summarizes much of the fundamental studies of electrospray. Several mathematical models have been generated to explsun the principals governing electrospray. Equation 1 defines the electric field Ec at the tip of a capillary of radius re with an applied voltage Vc at a distance d from a counter electrode held at ground potential: 2V E= ^ (1) r/n(4d/0 The electric field Eon required for the formation of a Taylor cone and liquid jet of a fluid flowing to the tip of this capillary is approximated as: ^^- 2ycos^r where y is the surface tension of the fluid, 9 is the half-angle of the Taylor cone and EQ is the permittivity of vacuum. Equation 3 is derived by combining equations I and 2 and approximates the onset voltage Von required to initiate an electrospray of a fluid fi-om a capillary: K. « rj cos9 in(Ad/r,) (3) As can be seen by examination of equation 3, the required onset voltage is more dependent on the capillary radius than the distance fiom the counter-electrode. It would be desirable to define an electrospray device that could fonn, a stable electrospray of all fluids commonly used in CE, CEC, and LC. The surface tension of solvents commonly used as the mobile phase for these separations range fi:om 100% aqueous (y = 0.073 N/m) to 100% methanol (y = 0.0226 N/m). As the surface tension of the electrospray fluid increases, a higher onset voltage is required to initiate an electrospray for a fixed capillary diameter. As an example, a capillary with a tip diameter of 14 pm is required to electrospray 100% aqueous solutions with an onset voltage of 1000 V. The work of M.S. Wihn et al., Int. J. Mass Spectrom. Ion Processes 136:167-80 (1994), first demonstrates nanoelectrospray firom a fiised-silica capillary pulled to an outer diameter of 5 pjn at a flow rate of 25 nL/min. Specifically, a nanoelectrospray at 25 nL/min was achieved from a 2 jim inner diameter and 5 pjn outer diameter pulled fiised-silica capillary with 600-700 V at a distance of 1-2 mm fi'om the ion-sampling orifice of an electrospray equipped mass spectrometer. Electrospray m front of an. ioa-sampUng orifice of an API mass spectrometer produces a quantitative response from the mass spectrometer detector due to the analyte molecules present in the liquid flowing from the capillary. One advantage of electrospray is that the response for an analyte measured by the mass spectrometer detector is dependent on the concentration of the analyte in the fluid and independent of the fluid flow rate. The response of an analyte in solution at a given concentration would be comparable using electrospray combined with mass spectrometry at a flow rate of 100 jiL/min compared to a flow rate of 100 nL/mJn. D.C. Gale et al.. Rapid Commun. Mass Spectrom. 7:1017 (1993) demonstrate that higher electrospray sensitivity is achieved at lower flow rates due to increased analyte ionization efficiency. Thus by performing electrospray on a fluid at flow rates in the nanoliter per minute range provides the best sensitivity for an analyte contained within the fluid when combined with mass spectrometry. Thus, it is desirable to provide an electrospray device for integration of microchip-based separation devices with API-MS instruments. This integration places a restriction on the capillary tip defining a nozzle on a microchip. This no^e will, in all embodiments, exist in^ a planar or near planar geometry with respect to the substrate defining the separation device and/or the electrospray device. When this co-planar or near planar geometry exists, the electric field lines emanating fix>m the tip of the nozzle will not be enhanced if the electric field around the nozzle is not defined and controlled and, therefore, an electrospray is only achievable with the application of relatively high voltages applied to the fluid. Attempts have been made to manufacture an electrospray device for microchip-based separations. Ramsey et al.. Anal. Chem. 69:1174-78 (1997) describes a microchip-based separations device coupled with an electrospray mass spectrometer. Previous work from this research group including Jacobson et al., Anal. Chem. 66:1114-18 (1994) and Jacobson et al., Anal. Chem. 66:2369-73 (1994) demonstrate impressive separations using on-chip fluorescence detection. This more recent work demonstrates nanoclectrospray at 90 nL/min from the edge of a planar glass microchip. The microchip-based separation channel has dimensions of 10 ^m deep, 60 ^tm wide, and 33 mm in length. Electroosmotic flow is used to generate fluid flow at 90 nL/mm. Application of 4,800 V to the fluid exiting the separation channel on the edge of the microchip at a distance of 3-5 mm from the ion-sampling orifice of an API mass specfrometer generates an electrospray. Approximately 12 nL of the sample fluid collects at the edge of the microchip before the formation of a Taylor cone and stable nanoelectrospray from the edge of the microchip. The volume of this microchip-based separation channel is 19.8 nL. Nanoelectrospray from the edge of this microchip device after capillary electrophoresis or capillary electrochromatography separation is rendered impractical since this system has a dead-volume approaching 60% of the column (channel) volume. Furthermore, because this device provides a flat surface, and, thiK, a relatively small amount of physical asperity for the formation of the electrospray, the device requires an impracticaJly high voltage to overcome the fluid surface tension to initiate an electrospray. Xue,,Q. et al., Anal. Chem. 69:426-30 (1997) also describes a stable nanoelectrospray from the edge of a planar glass microchip with a closed channel 25 \im deep, 60 )im wide, and 35-50 mm in length. An electrospray is formed by applying 4,200 V to the fluid exiting the separation channel on the edge of the microchip at a distance of 3-8 mm from the ion-sampling orifice of an API mass spectrometer. A syringe pump is utilized to deliver the sample fluid to the glass microchip at a flow rate of 100 to 200 nL/min. The edge of the glass microchip is treated with a hydrophobic coating to alleviate some of the difficulties associated with nanoelectrospray from a flat surface that slightly improves the stability of the nanoelectrospray. Nevertheless, the volume of the Taylor cone on the edge of the microchip is too large relative to the volume of the separation channel, making this method of electrospray directly from the edge of a microchip impracticable when combined with a chromatographic separation device. T. D. Lee et. al.. 1997 International Conference on Solid-State Sensors and Actuators Chicago, pp. 927-30 (June 16-19, 1997) describes a multi-step process to generate a nozzle on the edge of a silicon microchip 1-3 |jm in diameter or width and 40 ^m m length and applying 4,000 V to the entfre microchip at a distance of 0.25-0.4 mm from the ion-sampling orifice of an API mass spectrometer. Because a relatively high voltage is required to fomi an electrospray with the no22le positioned in very close proximity to the mass spectrometer ion-sampling orifice, this device produces an inefScient electrospray that does not allow for sufficient droplet evaporation before tiie ions enter the orifice. The extension of the nozzle firom tiie edge of the microchip also exposes the nozzle to accidental breakage. More recently, T. D. Lee et.al., m 1999 Twelfth IEEE International Micro Electro Mechanical Systems Conference (January 17-21, 1999), presented this same concept where the electrospray component was fabricated to extend 2.5 mm beyond the edge of the microchip to overcome this phenomenon of poor electric field control within the proximity of a surface. Thus, it is also desirable to provide an electrospray device with controllable spraying and a method for producing such a device that is easily ■ reproducible and manufacturable in high volumes. U.S. Patent 5,501,893 to Laermer et. al., reports a method of anisotropic plasma etching of silicon (Bosch process) that provides a method of producmg deep vertical structures that is easily reproducible and controllable. This method of anisotropic plasma etching of silicon incorporates a two step process. Step one is an anisotropic etch step using a reactive ion etching (RIE) gas plasma of suliiir hexafluoride (SFe). Step two is a passivation step that deposits a polymer on the vertical surfaces of the silicon substrate. This polymeri2ing step provides an etch stop on the vertical surface that was exposed in step one. Ihis two step cycle of etch and passivation is repeated until the depth of the desked structure is achieved. This method of anisotropic plasma etching provides etch rates over 3 (im/min of silicon depending on the aze of the feature being etched. The process also provides selectivity to etching siHcou versus silicon dioxide or resist of greater than 100:1 which is important when deep silicon stmctures are desired. Laenner et. al,, in 199! Twelfth IEEE International Micro Electro Mechanical Systems Conference f Januar 17-21,1999), reported improvements to the Bosch process. These improvements nclude silicon etch rates approaching 10 ^m/min, selectivity exceeding 300:1 to iilicon dioxide masks, and more uniform etch rates for features that vary in size. The present invention is directed toward a novel utilization of these "eatures to improve the sensitivity of prior disclosed microthip-based electrospray ;y stems. SUMMARY OF THE INVENTION Tlie present invention relates to an electrospray device for spraying a fluid which includes an insulating substrate having an injection surface and an ejection sxirface opposing die injection surface. The substrate is an integral monolith having either a single spray unit or a plurality of spray units for generating multiple sprays from a single fluid stream. Each spray unit includes an entrance orifice on the injection surface; an exit orifice on the ejection surface; a channel extending between the entrance orifice and the exit orifice; and a recess surrounding the exit orifice and positioned between the injection surface and the ejection surface. The entrance orifices for each of the pluraUty of spray units are in fluid commimication with one another and each spray unit generates an electrospray plume of the fluid. The electrospray device also includes an electric field generating source positioned to define an electric field surrounding the exit orifice. In one embodiment, the electric field generating source includes a first electrode attached to the substrate to impart a ■ first potential to the substrate and a second electrode to impart a second potential. The first and the second electrodes are positioned to define an electric field sunounding the exit orifice. This device can be operated to generate multiple electiospray plumes of fluid from each spray imit, to generate a single combined electrospray plume of fluid from a plurality of spray units, and to generate multiple electrospray plim^es of fluid from aplurality of spray units. The device can also be used in conjunction witii a system for processing an electrospray of fluid, a method of generating an electiospray of fluid, a method of mass spectrometiic analysis, and a method of liquid chromatographic analysis. Another aspect of the present invention is directed to an electrospray system for generating multiple sprays from a single fluid stieam. The system includes an array of a plurality of the above electiospray devices. The electrospray devices can be provided m the array at a device density exceeding about 5 devices/cm^, about 16 devices/cm^, about 30 devices/cm^, or about 81 devices/cm'^. The electrospray devices can also be provided in the array at a device density of from about 30 devices/cm^ to about 100 devices/ci^^. Another aspect of the present invention is directed to an array of a plurality of the above electrospray devices for generating multiple sprays from a single fluid stream. The electrospray devices can be provided in an array wherein the spacing on the ejection surface between adjacent devices is about 9 mm or less, about 4.5 mm or less, about 2.2 mm or less, about 1.1 mm or less, about 0.56 mm or less, or about 0.28 mm or less, respectively. Another aspect of the present invention is directed to a method of generating an electrospray wherein an electrospray device is provided for spraying a fluid. The electospray device includes a substrate having an injection surface and an ejection surface opposing the injection surface. TTie substrate is an integral monolith which includes an entrance orifice on the injection surface; an exit orifice on the ejection surface; a channel extending between the entrance orifice and ttie exit orifice; and a recess surrounding the exit orifice and positioned between the injection surface and the ejection surface. The method can be performed to generate multiple electrospray plumes of fluid from each spray unit, to generate a single combined electrospray plume of fluid fi-om a plurality of spray units, and to generate multiple electrospray plumes of fluid fiom a plurality of spray units. The electrospray device also includes an electric field generating source positioned to define an electric field surrounding the exit orifice. In one embodiment, the electric field generating source includes a first electrode attached to the substrate to impart a first potential to the substrate and a second electrode to impart a second potential. The first and the second electrodes are positioned to define an electric field surrounding the exit orifice. Analyte from a fluid sample is deposited on the injection surface and then eluted with an eluting fiuid. The eluting fluid containing analyte is passed into the entrance orifice through the channel and through the exit orifice. A first potential is appBed to the first electrode and a second potential is applied to the fluid through the second electrode. The first and second potentials are selected such that fluid discharged firom the exit orifice of each of the spray units forms an electrospray. Another aspect of the present invention is directed to a method of producing an electrospray device which includes providing a substrate having opposed first and second surfaces, each coated with a photoresist over an etch-resistant material. The photoresist on the first surface is exposed to an image to form a pattern in the form of at least one ring on the first surface. The photoresist on the first surface which is outside and inside the at least one ring is then removed to form an annular portion. The etch-resistant material is removed fixim the first surface of the substrate whore the photoresist is removed to form holes in the etch-resistant material. Photoresist remaining on the first surface is then optionally removed. The first surface is then coated with a second coating of photoresist. The second coating of photoresist within the at least one ring is exposed to an image and removed to form at least one hole. The material from the substrate coincident with the at least one hole in.the second layer of photoresist on the first surface is removed to form at least one passage extending through the second layer of photoresist on the first surface and into the substrate. Photoresist firom the first surface is then removed. An, etch-resistant layer is applied to all exposed surfaces on the first surface side of the substrate. The etch-resistant layer from the first surface that is around the at least one ring and iht material fi-om the substrate around the at least one ring are removed to define at least one nozzle on the first surface. The photoresist on the second surface is then exposed to an image to form a pattern circumscribing extensions of the at least one hole formed in the etch-resistant material of the first surface. The etch-resistant material on the second surface is then removed where the pattern is. Material is removed fi-om the substrate coincident with where the pattern in the photoresist on the second surface has been removed to form a reservoir extending into the substrate to the extent needed to join the reservoir and the at least one passage. An etch-resistant material is then applied to all exposed surfaces of the substrate to form the electrospray device. The method further includes the step of applying a silicon nitride layer over all surfaces after the etch-resistant material is applied to all exposed surfaces of the substrate. Another aspect of the present invention is directed another method of producing an electrospray device including providing a substrate having opposed first and second surfaces, the first side coated with a photoresist over an etch-resistant . material. The photoresist on the first surface is exposed to an image to form a pattern in the form of at least one ring on the first surface. The exposed photoresist is removed on the first surface which is outside and inside the at least one ring leaving the unexposed photoresist. The etch-resistant material is removed fi-om the first surface of the substrate where the exposed photoresist was removed to form holes in the etch-resistant material. Photoresist is removed from the first surface. Photoresist is provided over an etch-resistant material on the second surface and exposed to an image to form a pattern circumscribing extensions of the at least one ring formed in the etch-resistant material of the first surface.' The exDOsed nhotoresist on the second surface is removed. The etch-resistant material on the second surface is removed coincident with where the photoresist was removed. Material is removed from the substrate coincident with where the etch-resistant material on the second surface was removed to form a reservoir extending into the substrate. The remaining photoresist on the second surface is removed. The second surface is coated with an etch-resistant material. The first surface is coated with a second coating of photoresist The second coating of photoresist within the at least one ring is exposed to an image. The exposed second coating of photoresist is removed from within the at least one ring to form at least one hole. Material is removed from the substrate coincident with the at least one hole in the second layer of photoresist on the first surface to form at least one passage extending through the second layer of photoresist on the first surface and into substrate to the extent needed to reach the etch-resistant material coating the reservoir. Photoresist from the first surface is removed. Material is removed from the substrate exposed by the removed etch-resistant layer around the al least one ring to define at least one nozzle on the first surface. The etch-resistant material coating the reservoir is removed from the substrate. An etch resistant material is applied to coat all exposed surfaces of the substrate to form the electrospray device. The electrospray device of the present invention can generate multiple electrospray plumes from a single fluid stream and be simultaneously combined with mass spectrometry. Each electxospiiay plume generates a signal for an analyte contained within a fluid that is proportional to that analytes concentration. When multipie electrospray plumes are generated from one nozzle, the ion intensity for a given analyte will increase with the number of electrospray plumes emanating from that nozzle as measured by the mass spectrometer. When multiple nozzle arrays generate one or more electrospray plumes, the ion intensity will increase with the number of nozzles times Hae number of electrospray plumes emanating from the nozzle arrays. The present invention achieves a sigrdficant advantage in terms of high-sensitivity analysis of analytes by electrospray mass spectrometry. A method of control of tine electric field around closely positioned electrospray nozzles provides a method of generating multiple electrospray plumes from closely positioned nozdes in a well-controlled process. An array of electrospray nozzles is disclosed for'generation of multiple electrospray plumes of a solution for purpose of generating an ion - response as measured by a mass spectrometer that increases with the total number of generated electrospray plumes. The present invention achieves a significant advantage in comparison to prior disclosed electrospray systems and methods for combination with microfluidic chip-based devices incorporating a single nozzle forming a single electrospray. The electrospray device of the present invention generally includes a silicon substrate material defining a chamiel between an entrance orifice on an injection surface and a nozzle on an ejection surface (the major surface) such that the electrospray generated by the device is generally perpendicular to the ejection surfece. The nozzle has an inner and an outer diameter smd is ctefined by an annular portion recessed from the ejection surface. The recessed annular region extends radially from the outer diameter. The tip of the nozzle is co-planar or level with and does not extend beyond the ejection sxuface. Thus, the nozzle is protected against accidental breakage. The nozzle, the channel, and the recessed armular region are etched from the silicon substrate by deep reactive-ion etclung and other standard semiconductor processing techniques. Ail surfaces of the silicon substrate preferably have insulating layers thereon to electrically isolate the liquid sample from the substrate and the ejection and injection surfaces from each other such that different potential voltages may be individually applied to each surface, the silicon substrate and the liquid sample. The insulating layer generally constitutes a silicon dioxide layer combined with a silicon nitride layer. The silicon nitride layer provides a moisture barrier against water and ions from penetrating through to the substrate thus preventing electrical breakdown between a fluid moving in the channel and the substrate. The electrospray apparatus preferably includes at least one controlling elecfrode electrically contacting the substrate for the application of an electric potential to the substrate. Preferably, the nozzle, channel and recess are etched from the silicon substrate by reactive-ion etching and other standard semiconductor processing techniques. The injection-side features, through-substrate fluid channel, ejection-side features, and controlling electrodes are formed moiiolithically from a monocrystalline silicon substrate - i.e., they are formed during the course of and as a result of a fabrication sequence that requires no manipulation or assembly of separate components. Because the electrospray device is manufactured using reactive-ion etching and other standard semiconductor processing techniques, the dimensions of such a device nozzle can be very small, for example, as small as 2 ]xm inner diameter and 5 ^im outer diameter. Thus, a through-substrate fluid channel having, for example, 5 pm inner diameter and a substrate thickness of 250 jmi only has a volume of 4.9 pL C'picoliters"). The micrometer-scale dimensions of the electrospray device minimize the dead volume and thereby increase efficiency and analysis sensitivity when combined with a separation device. The electrospray device of the present invention provides for the efficient and effective formation of an electrospray. By providing an electrospray surface (i.e., the tip of the nozzle) from which the fluid is ejected with dimensions on the order of micrometers, the device limits the voltage required to generate a Taylor cone and subsequent electrospray. The nozzle of the electrospray device provides the physical asperity on the order of micrometers on which a large electric field is concentrated. Further, the nozzle of the electrospray device contains a thin region of conductive silicon insulated from a fluid moving through the nozzle by the insulating silicon dioxide and silicon nitride layers. The fluid and substrate voltages and the thickness of the insulating layers separating the silicon substrate from the fluid determine the electric field at the tip of the nozzle. Additional electrode(s) on the ejection surface to w^iich electric potential(s) may be applied and controlled independent of the electric potentials of the fluid and the substrate may be incorporated in order to advantageously modify and optimize the electric field in order to focus the gas phase ions produced by the electrospray. The microchip-based electrospray device of the present invention provides minimal extra-column dispersion as a result of a reduction in the extra-column volume and provides efficient, reproducible, reliable and rugged fonnation of an electrospray. This electrospray device is perfectiy suited as a means of electrospray of fluids from microchip-based separation devices. The design of this electrospray device is also robust such that the device can be readily mass-produced in a cost-effective, high-yielding process. The electrospray device may be interfaced to or integrated downstream from a sampling device, depending on the particular application. For example, the analyte may be electrosprayed onto a surface to coat that surface or into another device for purposes of conveyance, analysis, and/or synthesis. As described previously, highly charged droplets are formed at atmospheric pressure by the electrospray device from nanoliter-scaie volumes of an analyte. The highly charged droplets produce gas-phase ions upon sufEcient evaporation of solvent molecules which may be sampled, for example, through an ion-sampling orifice of an atmospheric pressure ionization mass spectrometer ("API-MS") for analysis of the electrosprayed fluid. A multi-system chip thus provides a rapid sequential chemical analysis system fabricated using Micro-ElectroMechanical System ("MEMS") technology. The multi-system chip enables automated, sequential separation and injection of a multiplicity of samples, resulting in significantly greater analysis throughput and utilization of the mass spectrometer instrument for high-throughput detection of compounds for drug discovery. Another aspect of the present invention provides a silicon microchip-based electrospray device for producing electrospray of a liquid sample. The electrospray device may be interfaced downstream to an atmospheric pressure ionization mass spectrometer ("API-MS") for analysis of the electrosprayed fluid. The use of multiple nozzles for electrospray of fluid from the same fluid stream extends the useful flow rate range of microchip-based electrospray devices. Thus, fluids may be introduced to the multiple electrospray device at higher flow rates as the total fluid flow is split between all of the nozzles. For example, by using 10 nozzles per fluid channel, the total flow can be 10 times higher than when using only one nozzle per fluid channel. Likewise, by using 100 nozzles per fluid channel, the total flow can be 100 times higher than when using only one nozzle per fluid channel. The fabrication methods used to form these electrospray nozzles allow for multiple nozzles to be easily combined with a single fluid stream channel greatiy extending the usefiil fluid flow rate range and increasing the mass spectral sensitivity for microfluidic devices. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1A shows a plan view of a one-nozzle electrospray device of the present invention. Figure IB shows a plan view of a two-nozzle electrospray device of the present invention. Figure 1C shows a plan view of a three-nozzle electrospray device of the present invention. Figure ID shows a plan view of a fourteen-nozzle electrospray device of the present invention. Figure 2A shows a perspective view of a one-nozzle electrospray device of the present mvention. Figure 2B shows a perspective view of a two-nozzle electrospray device of the present invention. Figure 2C shows a perspective view of a three-nozzle electrospray device of the present invention. Figure 2D shows a perspective view of a fourteen-nozzle electrospray device of the present invention. Figure 3A shows a cross-sectional view of a one-nozzle electrospray device of the present invention. Figure 3B shows a cross-sectional view of a two-nozzle electrospray device of the present invention. Figure 3C shows a cross-sectional view of a three-nozzle electrospray device of the present invention. Figure 3D shows a cross-sectional view of a fourteen-nozzle electrospray device of the present invention. Figure 4 is a perspective view of the injection or reservoir side of an electrospray device of the present invention. Figure 5 A shows a cross-sectional view of a two-nozzle electrospray device of the present invention generating one electrospray plume from each nozzle. Figure SB shows a cross-sectional view of a two-nozzle electrospray device of the present invention generating two electrospray plumes from each nozzle. Figure 6A shows a perspective view of a one-nozzle electrospray device of the present invention generating one electrospray plume from one nozzle. Figure 6B shows a perspective view of a one-nozzle electrospray device of the present invention generating two electrospray plumes from one nozzle. Figure 6C shows a perspective view of a one-nozzle electrospray device of the present invention generating three electrospray plumes from one nozzle. Figure 6D shows a perspective view of a one-nczzie electrospray device of the present invention generating four electrospray plumes from one nozzle. Figure 7A shows a video capture picture of a microfabricated electrospray nozzle generating one electrospray plume from one nozzle. Figure 7B shows a video capture picture of a microfabricated electrospray nozzle generating two electrospray plumes from one nozzle. Figure 8 A shows the total ion chromatogram ("TIC") of a solution imdergoing electrospray. Figure SB shows the mass chromatogram for the protonated analyte at m/z 315. Region 1 is the resulting ion mtensity from one electrospray plume from one nozzle. Region 2 is from two electrospray plumes from one nozzle. Region 3 is from three electrospray plumes from one nozzle. Region 4 is from four electrospray plumes from one nozzle. Region 5 is from two electrospray plumes from one nozzle. Figure 9A shows the mass spectrum from Region I of Figure 8B. Figure 93 shows the mass spectrum from Region 2 of Figiu"e SB. Figure 9C shows the mass spectrum from Region 3 of Figure 8B. Figure 9D shows the mass spectrum fiiam Region 4 of Figure 8B. Figure 10 is a chart ofthe ion intensity for m/z 315 versus the number of electrospray plumes emanating from one nozzle. Figure 11A is a plan view of a two by two array of groups of four nozzles of an electrospray device. Figure IIB is a perspective view of a two by two array of groups of four nozzles taken through a line through one row of nozzles. Figure UC is across-sectional view of a two by two array of groups of four nozzles of an electrospray device. Figure 12A is a cross-sectional view of a 20 ^m diameter nozzle with a nozzle height of 50 |im. The fluid has avoltageof.lOOOV, substrate has avoltageof zero V and a third electrode (not shown due to the scale of the figure) is located 5 mm from the substrate and has a voltage of zero V. The equipotential field lines are shown m increments of 50 V. , Figure 12B is an expanded region around the nozzle shown in Figure 12A. Figure 12C is a cross-sectional view of a 20 jim diameter nozzle with a nozzle height of 50 \im. The fluid has a voltage of 1 OOOV, substrate has a voltage of zero V and a third electrode (not shown due to the scale of the figure) is located 5 mm from the substrate and has a voltage of 800 V. The equipotentia] field hnes are shown m increments of 50 V. Figure 12D is across-secdonaiviewof a20 jim. diameter nozzle with a nozzle height of 50 ^un. The fluid has a voltage of 1 OOOV, substrate has a voltage of 800 V and a third electrode (not shown due to the scale of the figure) is located 5 mm ■ from the substrate and has a voltage of zero V. The equipotential field lines are shown in increments of 50 V. Figures 13A-13C are cross-sectional views of an electrospray device of the present invention illustrating the transfer of a discreet sample quantity to a reservoir contained on the substrate surface. Figure 13D is a cross-sectional view of an electrospray device of the present invention illustrating the evE^joration of the solution leaving an analyte contained within the fluid on the surface of the reservoir. Figure 13E is a cross-sectional view of an electrospray device of the present invention illustrating a fluidic probe sealed against the injection surface delivering a reconstitution fluid to redissolve the analyte for electrospray mass spectrometry analysis. Figure 14A is a plan view of mask one of an electrospray device. Figure 14B is a cross-sectional view of a silicon substrate 200 showing silicon dioxide layers 210 and 212 and photoresist layer 208. Figure 14C is a cross-sectional view of a silicon substrate 200 showing removal of photoresist layer 208 to form a pattern of 204 and 206 in the photoresist. Figure I4D is a cross-sectional view of a silicon substrate 200 showing removal of silicon dioxide 210 firom the regions 212 and 214 to expose the silicon substrate in these regions to form a pattern of 204 and 206 in the silicon dioxide 210. Figure 14E is a cross-sectional view of a silicon substrate 200 showing removal of photoresist 208. Figure 15A is a plan view of mask two of an electrospray device. Figure 15B is a cross-sectional view of a silicon substrate 200 of Figure 14E with a new layer of photoresist 208'. Figure 15C is a cross-sectional view of a silicon substrate 200 showing of removal of photoresist layer 208' to form a pattern of 204 in the photoresist and exposing the silicon substrate 218. Figure 15D is a cross-sectional view of a silicon, substrate 200 showing the removal of silicon substrate material from the region 218 to form a cylinder 224. Figure 15Eis across-sectional view of a silicon substrate 200 showing removal of photoresist 208'. Figure 15F is a cross-sectional view of a sihcon substrate 200 showing thermal oxidation of the exposed sihcon substrate 200 to fonn a layer of silicon dioxide 226 and 228 on exposed sihcon horizontal and vertical surfaces, respectively. Figure 15Gis a cross-sectional view of a silicon substrate 200 showing jelective removal of silicon dioxide 226 from all horizontal surfaces. Figure 15H is a cross-sectional view of a silicon substrate 200 showing removal of silicon substrate 220 to form an annular space 230 around the nozzles 232. Figure 16 A is a plan view of mask three of an electrospray device showing reservoir 234. Figure 16Bisacross-sectional viewof a sihcon substrate 200 of -igure 151 with a new layer of photoresist 232 on silicon dioxide 212. Figure 16C is a cross-sectional view of a sihcon substrate 200 showing emoval of photoresist layer 232 to form a pattern 234 m the photoresist exposing ihcon dioxide 236. Figure 16D is a cross-sectional view of a silicon substrate 200 showing emoval of silicon dioxide 236 from region 234 to ejqiose silicon 238 in the pattern of Figure 16E is a cross-sectional view of a silicon substrate 200 showing removal of silicon 238 fi-om region 234 to form reservoir 240 in the pattern of 234. Figure 16F is a cross-sectional view of a silicon substrate 200 showing removal of photoresist 232. Figure 16G is a cross-sectional view of a silicon substrate 200 showing thermal oxidation of the exposed silicon substrate 200 to form a layer of silicon dioxide 242 on all exposed silicon surfaces. Figure 16H is a cross-sectional view of a silicon substrate 200 showii^ low pressure vapor deposition of silicon nitride 244 confoimally coating all surfaces of the electrospray device 300. Figure 161 is a cross-sectional view of a silicon substrate 200 showing metal deposition of electrode 246 on silicon substrate 200. Figure 17A is a plan view of mask four of an electrospray device. Figure 17B is a cross-sectional view of a silicon substrate 300 showing silicon dioxide layers 310 and 312 and photoresist layer 30S. Figure 17C is a cross-sectional view of a silicon substrate 300 showmg removal of photoresist layer 308 to form a pattern of 304 and 306 in the photoresist Figure 17D is a cross-sectional view of a silicon substrate 300 showing removal of silicon dioxide 310 from the regions 318 and 320 to expose the silicon substrate in these regions to fonn a pattern of 204 and 206 in the silicon dioxide 310. Figure 17E is a cross-sectional view of a silicon substrate 300 showing removal of photoresist 308. Figure ISA is a plan view of mask five of an electrospray device. Figure 18B is a cross-sectional view of a silicon substrate 300 showing deposition of a film of positive-working photoresist 326 on the silicon dioxide layer 312. Figure 18C is a cross-sectional view of a silicon substrate 300 showing removal of exposed areas 324 of photoresist layer 326. Figure 18D is a cross-sectional view of a silicon substrate 300 showing etching of the oqjosed area 328 of the silicon dioxide layer 312. Figure 18E is a cross-sectional view of a silicon substrate 300 showing the etching of reservoir 332. FigiOT 18F is a cross-sectional view of a silicon substrate 300 showing removal of the remaining photoresist 326. Figure 18G is a cross-sectioiial view of a silicon substrate 300 showing deposition of the silicon dioxide layer 334. Figure 19A is a plan view of mask six of an electrospray device showing through-wafer channels 304. Figure 19B is a cross-sectional view of a silicon substrate 300 showing deposition of a layer of photoresist 308' on silicon dioxide layer 310. Figure 19C is a cross-sectional view of a silicon substrate 300 showing removal of the exposed area 304 of the photoresist. Figure 19D is across-sectional view of a silicon substrate 300 showing etching of the through-wafer channels 336. Figure 19E is a cross-sectional view of a silicon substrate 300 showing removal of photoresist 308'. Figure 19F is a cross-sectional view of a silicon substrate 300 showing removal of silicon substrate 320 to form an annular space 33S around the nozzles. Figure 19G is a cross-sectional view of a silicon substrate 300 showing removal of silicon dioxide layers 310,312 and 334. Figure 20A is a cross-sectional view of a silicon substrate 3 00 showing deposition of silicon dioxide layer 342 coating all silicon surfaces of the electrospray device 300. , Figure 20B is a cross-sectional view of a silicon substrate 300 showing deposition of silicon nitride layer 344 coating all surfaces of the electrospray device 300. Figure 20C is a cross-sectional view of a silicon substrate 300 showing metal deposition of electrodes 346 and 348. Figures 21A and 21B show a persp^ective view of scanning electron micrograph images of a multi-nozzle device fabricated in accordance with the present invention. DETAILED DESCRIPTION OF THE INVENTION Control of the electric field at the tip of a nozzle is an important component for successful generation of an electrospray for microfluidic microchip-based systems. This invention provides sufBcient control and definition of the electric field in and around a nosle microfabricated from a monolithic silicon substrate for the formation of multiple electrospray plumes from closely positioned nozzles. The present nozzle system is fabricated using Micro-EIectroMechanical System C'MEMS") fabrication technologies designed to micromachine 3-dimensional features from a silicon substrate. MEMS technology, in particular, deep reactive ion etching ("DRIE"), enables etcliing of the small vertical features required for the formation of micrometer dimension surfaces in the fonn of a nozzle for successfiil nanoelectrospray of fluids. Insulating layers of silicon dioxide and silicon nitride are also used for independent application of an electric field surrounding the nozzle, preferably by application of a potential voltage to a fluid flowing through the silicon device and a potential voltage applied to the silicon substrate. This independent apphcation of a potential voltage to a fluid exiting the nozzle tip and the silicon substrate creates a high electric field, on the order of 10^ V/m, at the tip of the nozzle. This high electric field at the nozzle tip causes the fonnation of a Taylor cone, fluidic jet and highly-charged fluidic droplets characteristic of the electrospray of fluids. These two voltages, the fluid voltage and the substrate voltage, control the formation of a stable electrospray from this microchip-based electrospray device. The electrical properties of silicon and silicon-based materials are well characterized. The use of silicon dioxide and silicon nitride layers grown or deposited on the surfaces of a silicon substrate are well known to provide electrical insulating properties. Incorporating silicon dioxide and silicon nitride layers in a monolithic silicon electrospray device with a defined nozzle provides for the enhancement of an electric field in and around features etched from a monolithic silicon substrate. This is accompUshed by independent application of a voltage to the fluid exiting the nozzle and the region surrounding the nozzle. Silicon dioxide layers may be grown thermally in an oven to a desired thickness. Silicon nitride can be deposited using low pressure chemical vapor deposition ("LPCVD")- Metals may be further vapor deposited on these surfaces to provide for application of a potential voltage on the surface of the device. Both silicon dioxide and silicon nitride fiinction as electrical insulators allowing the application of a potential voltage to the substrate thai is different than that apphed to the surface of the device. An important feature of a silicon nitride layer is that it provides a moisture barrier between the silicon substrate, silicon dioxide and any fluid sample that comes in contact with the device. Silicon nitride prevents water and ions from difiiising through the silicon dioxide layer to the silicon substrate which may cause an electrical breakdown between the fluid and the sihcon substrate. Additional layers of sihcon dioxide, metals and other materials may . further be deposited on the silicon nitride layer to provide chemical functionality to silicon-based devices. Figures lA- ID show plan views of 1, 2, 3 and 14 nozzle electrospray devices, respectively, of the present invention. Figures 2A - 2D show perspective views of the nozzle side of an electrospray device showing 1, 2, 3 and 14 nozzles 232, respectively, etched from the silicon substrate 200. Figures 3A - 3D show cross-sectional views of 1,2,3 and 14 nozzle electrospray devices, respectively. The nozzle or ejection side of the device and the reservoir or injection side of the device are connected by the thiough-wafet channels 224 thus creating a fluidic path through the silicon substrate 200. Fluids may be introduced to this microfabricated electrospray device by a fluid delivery device, such as a probe, condtiit, capillary, micropipette, microchip, or the like. The perspective view of Figure 4 shows a probe 252 that moves into contact with the injection or reservoir side of the electrospray device of the present invention. The probe can have a disposable tip. This fluid probe has a seal, for example an o-ring 254, at the tip to form a seal between the probe tip and the injection surface of the substrate 200. Figure 4 shows an array of a plurality of electrospray devices fabricated on a monohthic substrate. One liquid sample handling device is shown for clarity, however, multiple liquid sampling devices can be utilized to provide one or more fluid samples to one or more electrospray devices in accordance with the present invention. The fluid probe and the substrate can be manipulated in 3-dimensions for staging of, for example, different devices in front of a mass spectrometer or other sample detection apparatus. As shown in Figure 5, to generate an electrospray, fluid may be delivered to the through-substrate channel 224 of the electrospray device 250 by, for example, a capillary 256, micropipette or microchip. The fluid is subjected to a potential voltage, for example, in the capillary 256 or in the reservoir 242 or via an electrode provided on the reservoir surface and isolated from the surrounding surface region and the substrate 200. A potential voltage may also be applied to the silicon substrate via the electrode 246 on the edge of the silicon substrate 200 the magnitude of which is preferably adjustable for optimizatioii of the electrospray characteiistics. The fluid flows through the channel 224 and exits from the nozzle 232 in the form of a Taylor cone 258, liquid jet 260, and very fine, highly charged fluidic droplets 262. Figure 5 shows a cross-sectionaj view of a two-nozzle array of the present invention. Figure 5A shows a cross-sectional view of a 2 nozzle electrospray device generating one electrospray plume from each nozzle for a single fluid stream. Figure 5B shows a cross-sectional view of a 2 nozzle electrospray device generating 2 electrospray plumes from each nozzle for a single fluid stream. The nozzle 232 provides the physical asperity to promote the formation ofaTaylorcone258aiidefficientelectrospray262ofafluid256. Thenozzle232 . also forms a continuation of and serves as an exit orifice of the through-wafer channel 224. The recessed annular region 230 serves to physically isolate the nozzle 232 from the surface. The present invention allows the optimization of the electric field lines emanating from the Quid 256 exiting the nozzle 232, for example, through independent control of the potential voltage of the fluid 256 and the potential voltage ofthe substrate 200. Figures 6A - 6D illustrate 1,2, 3 and 4 electrospray plumes, respectively, generated from one nozzle 232. Figures 7A - 7B show video capture pictures of a microfabricated electrospray device of the present invention generating one electrospray plume from one nozzle and two electrospray plumes from one nozzle, respectively. Figure 8 shows mass spectral results acquired from a microfabricated electrospray device ofthe present invention generating from 1 to 4 electrospray plumes from a single nozzle. The applied fluid potential voltage relative to the applied substrate potential voltage controls the number of electrospray plumes generated. Figure 8A shows the total ion chromatogram ("TIC") of a solution containing an aualyte at a concentration of 5 ^M resulting from electrospray ofthe fluid from a microfabricated electrospray device ofthe present invention. The substrate voltage for this example is held at zero V while the.-fluid voltage is varied to control th6 number of electrospray plumes exiting the nozzle. Figure 8B shows the selected mass chiomatogram for the analyte at m/z 315. In this example, Region I has one electrospray plume exiting the nozzle tip with a fluid voltage of 950V. Region II has two electrospray plumes exiting the nozzle tip with a fluid voltage of 1050V. Region lH has three electrospray plumes exiting the nozzle tip with a fluid voltage of 1150 V. Region IV has four electrospray plumes exiting the nozzle tip with a fluid voltage of 1250V. Region V has two electrospray plumes exiting the nozzle tip. Figure 9A shows the mass spectrum resulting from Region I with one electrospray piume. Figure 9B shows the mass spectrum resulting from Region H with two electrospray plumes. Figilre 9C shows the mass ^ectnim resulting from Region IH with three electrospray plumes. Figure 9D shows the mass spectrum resulting from Region IV with four electrospray plumes exiting the nozzle tip. It is clear from the results that this invention can provide an increase in the analyte response measured by a mass spectrometer proportional to the number of electrospray plumes exiting the nozzle tip. Figure 10 charts the ion intensity for m/z 315 for I, 2, 3 and 4 electrospray plumes exiting the nozzle tip. Figures 11A - 11C illustrate a system having a two by two array of electrospray devices. Each device has a group of four electrospray nozzles in fluid communication with one common reservoir containing a single fluid sample source. Thus, this system can generate multiple sprays for each fluid stream up to foiir different fluid streams. The electric field at the nozzle tip can be simulated using SIMI01 closer the equipotential lines are spaced the higher the electric field. The simulate electric field at the fluid tip with these dimensions and potential voltages is 8.2 X 10 V/m. Figure 12B shows an expanded region around the nozzle of Figure 12A to show greater detail of the eqmpotential lines. Figure 12C shows the equipotential lines around this same nozzle with a fluid potential voltage of 1OOOV substrate voltage of zero V and a third electrode voltage of 800 V. The electric fie at the nozzle tip is 8.0 x IO' V/m indicating that the applied voltage of this third electrode has little effect on the electric field at the nozzle tip. Figure 12D shows t electric field lines around this same nozzle with a fluid potential voltage of 1 OOOV, substrate voltage of 800 V and a third electrode voltage of 0 V. The electric field s the nozzle tip is reduced significantly to a value of 2.2x10^ V/m. This indicates ti very fine control of the electric field at the nozzle tip is achieved with this inventio: by independent control of the applied fluid and substrate voltages and is relatively insensitive to other electrodes placed up to 5 mm fiom the device- TTiis level of control of the electric field at the nozzle tip is of significant importance for electrospray of fluids firom a nozzle co-planar with the surface of a substrate. This fine control of the electric field allows for precise control of th( electrospray of fluids from these nozzles. When electrospraying flmds firom this invention, this fine control of the electric field allows for a controlled formation of multiple Taylor cones and electrospray plumes fi-om a single nozzle. By simply increasing the fluid voltage while maintaining the substrate voltage at zero V, the number of electrospray plumes emanating fi-om one nozzle can be stepped from oni to four as illustrated in Figures 6 and 7. The high electric field at the nozzle tip applies a force to ions contained within the fluid exiting the nozzle. This force pushes positively-charged ions to the fluid surface when a positive voltage is applied to the fluid relative to th substrate potential voltage. Due to the repulsive force of likely-charged ions, the surface area of the Taylor cone generally defines and limits the total nimiber of ion; that can reside on the fiuidic surface. It is generally believed that, for electrospray, gas phase ion. for an analyte can most easily be formed by that analyte when it resid on the surface of the fluid. The total surface area of the fluid increases as the numb of Taylor cones at the no2zle tip increases resulting in the increase in solution phast ions at the surface of the fluid prior to electrospray formation. The ion intensity wi increase as measured by the mass spectrometer when the number of electrospray plumes increase as shown in the example above. Another important feature of the present invention is that since the electric field around each nozzle is preferably defined by the fluid and substrate voltage at the nozzle tip, multiple nozzles can be located in close proximity, on the order of tens of microns. This novel feature of the present invention allows for the formation of multiple electrospray plumes from multiple nozzles of a single fluid stream thus greatly increasing the electrospray sensitivity available for microchip-based electrospray devices. Multiple nozides of an elecfrospray device m fluid communication with one another not only improve sensitivity but also increase the flow rate capabilities of the device. For example, the flow rate of a single fluid stream through one nozzle having the dimensions of a 10 micron inner diameter, 20 micron ■ outer diameter, and a 50 micron length is about 1 [iL/min.; and the flow rate through 200 of such nozzles is about 200 fiL/min. Accordingly, devices can be fabricated having the capacity for flow rates up to about 2 ^iL/min., from about 2 fiL/min. to about 1 mL/min., from about 100 nL/min. to about 500 nL/min., and greater than about 2 )iL/min. possible. Arrays of multiple electrospray devices having any nozzle number and format may be fabricated according to the present invention. The electrospray devices can be positioned to form from a low-density array to a high-density array of devices. Arrays can be provided having a spacing between adjacent devices of 9 mm, 4.5 mm, 2.25 mm, 1.12 mm, 0.56 ram, 0.28 mm, and smaller to a spacing as close as about 50 p,m apart, respectively, which correspond to spacing used in commercial instrumentation for liquid h^idling or accepting samples from electrospray systems. Similarly, systems of electrospray devices can be fabricated in an array having a device density exceeding about 5 devices/cm^, exceeding about 16 devices/cm , exceeding about 30 devices/cm'^, and exceeding about 81 devices/cm^, preferably from about 30 devices/cm^ to about 100 devices/cm^. Dimensions of the electrospray device can be determined according to various factors such as the specific application, the layout design as well as the upstream and/or downstream device to which the electrospray device is interfaced or integrated. Further, the dimensions of the channel and nozzle may be optimized for the desired flow rate of the fluid sample. The use of reactive-ion etching techniques allows for the reproducible and cost effective production of small diameter nozzles, for example, a 2 ^m inner diameter and 5 jjin outer diameter. Such nozzles can be ' fabricated as close as 20 ]xai apart, providing a density of up to about 160,000 nozzles/cm . Nozzle densities up to about lO,000/cm^, up to about 15,625/cm^, up to about 27,566/cm^, and up to about 40,000/cm^, respectively, can be provided within an electrospay device. Similarly, nozzles can be provided wherein the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is less than about 500 \im, less than about 200 ^im, less than about 100 [im, and less than about 50 Mm, respectively. For example, an electrospray device having one nozzle with an outer diameter of 20 \U3\ would respectively have a surrounding sample well 30 jim wide. A densely packed array of such nozzles could be spaced as close as 50 pm apart as measured fi-om the nozzle center. In one currently preferred embodiment, the silicon substrate of the electrospray device is approximately 250-500 fim in thickness and the cross-sectional area of the through-substrate channel is less than approximately 2,500 fim^. Where the channel has a circular cross-sectional shape, the channel and the nozzle have an inner diameter of up to 50 )im, more preferably up to 30 pm; the nozzle has an outer diameter of up to 60 [im, more preferably up to 40 |im; and nozzle has a height of (and the annular region has a depth of) up to 100 |jjn. The recessed portion preferably extends up to 300 jim outwardly ftoia. the nonle. The silicon dioxide layer has a thicknessof approximately 1-4 ^mi, preferably 1-3 |im. The silicon nitride layer has a thickness of approximately less than 2 [un. Furthermore, the electrospray device may be operated to produce larger, minimally-charged droplets. This is accompHshed by decreasing the electric field at the nozzle exit to a value less than that reqmred to generate an electrospray of a given fluid. Adjustmg the ratio of the potential voltage of the fluid and the potential voltage of the substrate controls the electric field. A fluid to substrate potential voltage ratio approximately less than 2 Is preferred for droplet formation. The droplet thameter in this mode of operation is controlled by the fluid surface tension, applied voltages and distance to a droplet receiving well or plate. This mode of operation is ideally suited for conveyance and/or apportionment of a multiplicity of discrete amounts of fluids, and may find use in such devices as ink jet printers and equipment and instruments requiring controlled distribution of fluids. The electrospray device of the present invention includes a silicon substrate material defining a channel between an entrance orifice on a reservoir surface and a no2zie on a nozzle surface such that the electrospray generated by the device is generally perpendicular to the nozzle surface. The nozzle has an inner and an outer diameter and is defined by an annular portion recessed from the surface. The recessed annular region extends radially from the nozzle outer diameter. The tip of the nozzle is co-planar or level with and preferably does not extend beyond the substrate surface. In this manner the nozzle can be protected agmnst accidental breakage. The nozzle, channel, reservoir and the recessed annular region are etched from the silicon substrate by reactive-ion etching and other standard semiconductor processing techniques. All surfaces of the silicon substrate preferably have insulating layers to electrically isolate the liquid sample from the substrate such that different potential voltages may be individually applied to the substrate and the liquid sample. The insulating layers can constitute a sihcon dioxide layer combined with a silicon nitride layer. The silicon nitride layer provides a moisture barrier against water and ions from penetrating through to the substrate causing electrical breakdown between a fluid moving in the channel and the substrate. The electrospray apparatus preferably includes at least one controlling electrode electrically contacting the substrate for the apphcation of an electric potential to the substrate. Preferably, the nozzle, channel and recess are etched from the silicon substrate by reactive-ion etching and other standard semiconductor processing techniques. The nozzle side features, through-substrate fluid chaimel, reservoir side features, and controlling elecfrodes are preferably formed monolithically from a monocrystalline silicon substrate — i.e., they are formed during the course of and as a result of a fabrication sequence that requires no manipulation or assembly of separate components. Because the electrospray device is manufactured using reactive-ion etching and other standard semiconductor processing techniques, the dimensions of such a device can be very small, for example, as small as 2 pm inner diameter and 5 ^mi outer diameter. Thus, a through-substrate Quid charmel having, for example,- 5 (im inner diameter and a substrate thickness of 250 \mx only has a volume of 4.9 pL. The micrometer-scale dimensions of the electrospray device minimize the dead volume and thereby increase efficiency and analysis sensitivity when combined with a separation device. The electrospray device of the present invention provides for the efficient and effective formation of an electrospray. By providing an electrospray surface &om which the fluid is ejected with dimensions on the order of micrometers, the electrospray device Umits the voltage required to generate a Taylor cone as the voltage is dependent upon the nozzle diameter, the surfece tension of the fluid, and the distance of the nozzle &om an extracting electrode. The nozzle of the electrospray device provides (he physical asperity on the order of micrometers on v^ch a large electric field is concentrated. Further, the electrospray device may provide additional electrode(s) on the ejecting surface to which electric potential(s) may be applied and controlled independent of the electric potentials of the fluid and the extracting electrode in order to advantageously modiiy and optimize the electric field in order to focus the gas phase ions resulting from electrospray of fluids. The combination of the nozzle and the additional electrode(s) thus enhance the electric field between the nozzle, the substrate and the extracting electrode. The electrodes are preferable positioned within about 500 microns, and more preferably within about 200 microns from the exit orifice. The microchip-based electrospray device of the present invention provides minimal extra-column dispersion as a result of a reduction in the extra-column volume and provides efficient, reproducible, reliable and rugged formation of an electrospray. This electrospray device is perfectly suited as a means of electrospray of fluids from microchip-based separation devices. The design of this electrospray device is also robust such that the device can be readily mass-produced in a cost-effective, high-yielding process. In operation, a conductive or partly conductive liquid sample is introduced into the through-substrate channel entrance orifice on the injection surface. The Uquid is held at a potential voltage, either by means of a conductive fluid delivery device to flie electrospray device or by means of an electrode formed on the injection surface isolated from the surrounding surface region and from flie substrate. The electric field strength at the tip of the nozzle is enhanced by the application of a voltage to the substrate and/or the ejection surface, preferably zero volts up to approximately less than one-half of the voltage applied to the fluid. Thus, by the independent control of the fluid/nozzle and substrate/ejection surface voltages, the electrospray device of the present invention allows the optimization of the electric field emanating &om the nozzle. The electrospray device of the present invention may be placed 1-2 mm or up to 10 mm fi:om the orifice of an atmospheric pressure . ionization ("API") mass spectrometer to establish a stable nanoelectrospray at flow rates in the range of a few nanoUters per minute. The electrospray device may be interfeced or integrated downstream to a sampling device, depending on the particular application. For example, the analyte may be electrosprayed onto a surface to coat that surface or into another device for purposes of conveyance, ai^ysis, and/or synthesis. As described above, lughly charged droplets are formed at atmospheric pressure by the electrospray device from nanoUter-scale volumes of an analyte. The highly charged droplets produce gas-phase ions upon sufficient evaporation of solvent molecules which may be sampled, for example, through an ion-sampling orifice of an atmospheric pressure ionization mass spectrometer ("API-MS") for analysis of the electrosprayed fluid. One embodiment of the present invention is in the form of an array of multiple electrospray devices which allows for massive parallel processing. The multiple electrospray devices or systems fabricated by massively parallel processing on a single wafer may then be cut or otherwise separated into multiple devices or , systems. The electrospray device may also serve to reproducibly distribute and deposit a sample from a mother plate to daughter plate(s) by nanoelectrospray deposition or by the droplet method. A chip-based combinatorial chemistry system including a reaction well block may define an array of reservoirs for containing the reaction products from a combinatorially synthesized compound. The reaction well block further defines channels, nozzles and recessed portions such tiiat die fluid in each reservoir may flow through a corresponding channel and exit through a corresponding nozzle in the form of droplets. The reaction well block may define any number of reservoir(s) in any desirable configuration, each reservoir being of a suitable dimension and shape. The volume of a reservoir may range from a few picoliters up to several microhters. The reaction well block may serve as a mother plate to interface to a microchip-based chemical synthesis apparatus such that the droplet method of the electrospray device may be utilized to reproducibly distribute discreet quantities of the product solutions to a receiving or daughter plate. The daughter plate defines receiving wells that correspond to each of the reservoirs. The distributed product solutions in the daughter plate may then be utilized to screen the combinatorial chemical library against biological targets. The electrospray device may also serve to reproducibly distribute and deposit an array of samples iiom a mother plate to daughter plates, for example, for proteomic screening of new drug candidates. This may be by either droplet formation or electrospray modes of operation. Electrospray device(s) may be etched into a microdevice capable of synthesizing combinatorial chemical libraries. At a desired time, a norzIe(s) may apportion a desired amount of a sample(s) or reagent(s) &om a mother plate to a daughter plate(s). Control of the nozzle dimensions, applied voltages, and time provide a precise and reproducible method of sample apportionment or deposition from an array of nozzles, such as for the generation of sample plates for molecular weight determinations by matrix-assisted laser desorpticn/ionization time-of-flight mass spectrometry ("MALDI-TOFMS"). The capability of transferring analytes from a mother plate to daughter plates may also be utilized to make other daughter plates for other types of assays, such as proteomic screening. The fluid to substrate potential voltage ratio can be chosen for formation of an electrospray or droplet mode based on a particular application. An array of multiple electrospray devices can be configured to disperse ink for use in an ink jet printer. The control and enhancement of the electric field at the exit of the nozzles on a substrate will allow for a variation of ink apportionment schemes including the formation of droplets approximately two times the nozzle diameters or of submicometer, highly-charged droplets for blending of different colors of ink. The electrospray device of the present invention can be integrated with miniaturized liquid sample handling devices for efficient electrospray of the liquid samples for detection using a mass spectrometer. The electrospray device may also be used to distribute and apportion fluid samples for use with high-throughput screen technology. The electrospray device may be chip-to-chip or wafer-to-wafer, bonded tO- plastic, glass, or silicon microchip-based liquid separation devices capable of, for example, capillary electrophoresis, capillary electrochromatography, af&nity chromatography, liquid chromatography ("LC"), or any other condensed-phase separation technique. An array or matrix of multiple electrospray devices of the present invention may be manufactured on a single microchip as silicon fabrication using standard, well-controlled thin-fihn processes. This not only eliminates handling of such micro components but also allows for rapid parallel processing of functionally similar elements. The low cost of these electrospray devices allows for one-time use such that cross-contamination from different liquid samples may be eliminated. Figures 13A- 13E illustrate the deposition of a discreet sample onto an electrospray device of the present invention. Figures 13A - 13C show a fluidic probe depositing or transferring a sample to a reservoir on the injection surface. The fluidic sample is delivered to the reservoir as a discreet volume generally less than lOOnL. The'dots'represent analytes contained within a fluid. Figure 13D shows the fluidic sample volume evaporated leaving the analytes on the reservoir surface. This reservoir surface may be coated with a retentive phase, such as a hydrophobic C18-like phase commonly used for LC applications, for increasing the partition of analytes contained within the fluid to the reservoir surface. Figure 13E shows a fluidic probe sealed against the injection surface to deliver a fluidic mobile phase to the microchip to reconstitute the transferred analytes for analysis by electrospray mass spectrometey. The probe can have a disposable tip, such as a capillary, micropipette, or microchip. A mtilti-system chip thus provides a rapid sequential chemical analysis system fabricated using Micro-ElectroMechanical System ("MEMS") technology. For example, the multi-system chip enables automated, sequential separation and injectionof a multiplicity of samples, resulting in significantly greater analysis throughput and utilization of the mass spectrometer instrument for, for example, high-thioughput detection of compounds for drug discovery. Another aspect of the present invention provides a silicon microchip-based electrospray device for producing electrospray of a liquid sample. The electrospray device may be interfaced downstream to an atmospheric pressure ionization mass spectrometer ("API-MS") for analysis of the electrosprayed fluid. Another aspect of the invention is an integrated miniaturized liquid phase separation device, which may have, for example, glass, plastic or silicon substrates integral with the electiospray device. Electrospray Device Fabrication Procedure The electrospray device 250 is preferably fabricated as a monolithic silicon substrate utilizing well-established, controlled thin-film silicon processing techniques such as thermal oxidation, photolithography, reactive-ion etching (RIE), chemical vapor deposition, ion implantation, and metal deposition. Fabrication using such silicon processing techniques facilitates massively parallel processing of similar devices, is time- and cost-ef&cient, allows for tighter control of critical dimensions, is easily reproducible, and results in a wholly integral device, thereby eliminating any assembly requirements. Further, the fabrication sequence may be easily extended to create physical aspects or features on the injection surface and/or ejection surface of the electrospray device to facilitate interfacing and connection to a fluid delivery system or to facilitate integration with a fluid delivery sub-system to create a single integrated system. Nozzle Surface Processing: Figures 14A- 14E and Figures 15A - 151 illustrate the processing steps for the nozzle or ejection side of the substrate in fabricating the electrospray device of the present invention. Referring to the plan view of Figure 14A, a mask is used to pattern 202 that will form the nozzle shape in the completed electrospray device 250. The patterns in the form of circles 204 and 206 forms through-wafer channels and a recessed annular space around the nozzles, resp«:tively of a completed electrospray device. Figure 14B is the cross-sectional view taken along line 14B-14B of Figure 14A. A double-side polished silicon wafer 200 is subjected to an elevated temperature in an oxidizing environment to grow a layer or filTn of silicon dioxide 210 on the nozzle side and a layer or film of silicon dioxide 212 on the reservoir side of the substrate 200. Each of the resulting siUcon dioxide layers 210,212 has a thickness of approximately 1-3 ^mi. The silicon dioxide layers 210,212 serve as masks for subsequent selective etching of certain areas of the silicon substrate 200. A film of positive-working photoresist 208 is deposited on the silicon dioxide layer 210 on the nozzle side of the substrate 200. Referring to Figure 14C, an area of the photoresist 204 corresponding to the entrance to through-wafer channels and an area of photoresist corresponding to the recessed annular region 206 which will be subsequently etched is selectively exposed through a mask (Figure 14A) by an optical lithographic exposure tool passing short-wavelength light, such as blue or near-uitraviolet at wavelengths of 365,405, or 436 nanometers. As shown in the cross-sectional view of Figure 14C, after development of the photoresist 208, the exposed area 204 of the photoresist is removed and open to the underlying sihcon dioxide layer 214 and the exposed area 206 of the photoresist is removed and open to the imderlying silicon dioxide layer 216, while the unexposed areas remain protected by photoresist 208. Referring to Figure 14D, the exposed areas 214, 216 of the silicon dioxide layer 210 is then etched by a fluorine-based plasma with a high degree of anisotropy and selectivity to the protective photoresist 20S until the silicon substrate 218, 220 are reached. As shown in the cross-sectional view of Figure 14E, the remaining photoresist 208 is removed from the silicon substrate 200. Referring to the plan view of Figure ISA, a mask is used to pattern 204 in the form of circles. Figure 15B is the cross-sectional view taken along line 15B-15B of Figure 15A. A film of positive-working photoresist 208' is deposited on the silicon dioxide layer 210 on the nozzle side of the substrate 200. Referring to Figure 15C, an area of the photoresist 204 corresponding to the entrance to through-wafer chaimels is selectively exposed through a mask (Figure 15A) by an optical lithographic exposure tool passing short-wavelength hght, such as blue or near-ultraviolet at wavelengths of 365, 405, or 436 nanometers. As shown in the cross-sectional view of Figure 15C, after development of the photoresist 208', the exposed area 204 of the photoresist is removed to the underlying silicon substrate 218, The remaining photoresist 208' is used as a mask during the subsequent fluorine based DRIE silicon etch to vertically etch the through-wafer channels 224 shown in Figure 15D. After etching the through-wafer chaimels 224, the remaining photoresist 208' is removed from tlie silicon substrate 200. As shown m the cross-sectional view of Figure 15E, the removal of the photoresist 208' exposes the mask pattern of Figure 14A formed m the silicon dioxide 210 as shown in Figurel4E. Referring to Figure 15F, the silicon wafer of Figure 15E is subjected to an elevated temperature in an oxidizing environment to grow a layer or film of silicon dioxide 226, 228 on all exposed silicon surfeces of the wafer. Referring to Figure 15G, the silicon dioxide 226 is then etched by a fluorine-based plasma with a high degree of anisptropy and selectivity until the silicon substrate 220 is reached. The silicon dioxide layer 228 is designed to serve as an etch stop during the DRIE etch of Figure 15H that is used to form the nozzle 232 and recessed annular region 230. An advantage of the fabrication process described herein is ttiat the process simplifies the ahgnment of the through-wafer channels and the recessed. annular region. This allows the fabrication of smaller nozzles with greater ease without any complex alignment of masks. Dimensions of the through channel, such as the aspect ratio (i.e. depth to width), can be reliably and reproducibly limited and controlled. Reservoir Surface Processing: Figures 16A - 161 illustrate the processing steps for the reservoir or injection side of the substrate 200 in fabricating the electrospray device 250 of the present invention. As shown in the cross-sectional view in Figure 16B (a cross-sectional view taken along line I6B-16B of Figure 16A), a film of positive-working photoresist 236 is deposited on the silicon dioxide layer 212. Patterns on the reservoir side are aligned to those previously formed on the nozzle side of the substrate using through-substrate alignments. After alignment, an area of the photoresist 236 corresponding to the circular reservoir 234 is selectively exposed through a mask (Figure 16A) by an optical lithographic exposure tool passing short-wavelength light, such as blue or near-ultraviolet at wavelengths of 365,405, or 436 nanometers. As shown in the cross-sectional view of Figure 16C, the photoresist 236 is then developed to remove the exposed areas of the photoresist 234 such that the reservoir region is open to the underlying silicon dioxide layer 238, while the unexposed areas remain protected by photoresist 236. The exposed area 238 of the silicon dioxide layer 212 is then etched by a fluorine-based plasma with a high degree of anisotropy and selectivity to the protective photoresist 236 until the silicon substrate 240 is reached as shown in Figure 16D. As shown in Figure 16E, a fluorine-based etch creates a cylindrical region that defines a reservoir 242. The reservoir 242 is etched until the through-wafer channels 224 are reached. After the desired depth is achieved the remaining photoresist 236 is then removed in an oxygen plasma or in an actively oxidiz chemical bath like suifiiric acid (H2SO4) activated with hydrogen peroxide Qii^u, Preparation of the Substrate for £)ectrica] Isolation Referring to Figure 16G, the silicon wafer 200 is subjected to an elevated temperature in an oxidizing environment to grow a layer or film of sihcon dioxide 244 on all silicon surfaces to a thickness of approximately 1-3 fim. The sihcon dioxide layer serves as an electrical insulating layer. Silicon nitride 246 is further deposited using low pressure chemical vapor deposition (LPCVD) to provide a confoimal coating of sihcon nitride on all surfaces up to 2 iim in thickness, as shown m Figure 16H. LPCVD silicon nitride also provides further electrical insulation and a fluid barrier that prevents fluids and ions contained therein that are introduced to the electrospray device from causing an electrical connection between the fluid the sihcon substrate 200. This allows for the mdependent application of a potential voltage to a fluid and the subsh^te with this electrospray device to generate the high electric field at the nozzle tip required for successful nanoelectrospray of fluids from microchip devices. After fabrication of multiple electrospray devices on a single silicon wafer, the wafer can be diced or cut into individual devices. This exposes a portion of the silicon substrate 200 as shown in the cross-sectional view of Figure 161 on which a layer of conductive metal 248 is deposited. All sihcon surfaces are oxidized to form silicon dioxide with a thickness that is controllable through choice of temperature and time of oxidation. All sihcon dioxide surfaces are LPCVD coated with silicon nitride. The final thickness of the sihcon dioxide and silicon nitride can be selected to provide the desired degree of electrical isolation in the device. A thicker layer of silicon dioxide and sihcon nitride provides a greater resistance to electrical breakdown.- The sihcon substrate is divided into the desired size or array of electrospray devices for purposes of metalization of the edge of the silicon substrate. As shown in Figure 161, the edge of the silicon substrate 200 is coated with a conductive material 248 using well known thermal evaporation and metal deposition techniques. The fabrication method confers superior mechanical stability to the fabricated electrospray device by etching the features of the electrospray device &om a monocrystalline silicon substrate without any need for assembly. The alignment scheme allows for nozzle walls of less than 2 ^m and no^e outer diameters down to 5 fim to be febricated reproducibly. Further, the lateral extent and shape of the recessed annular region can be controlled independently of its depth. The depth of the recessed annular region also determines the nozzle height and is determined by the extent of etch on the nozzle side of the substrate. The above described fabrication sequence for the electrospray device can be easily adapted to and is applicable for the simultaneous fabrication of a single monolithic system comprising multiple electrospray devices including multiple channels and/or multiple ejection nozzles embodied in a single monolithic substrate. Further, the processing steps may be modified to fabricate similar or different electrospray devices merely by, for example, modifying the layout design and/or by changing the polarity of the photomask and utilizing negative-working photoresist rather than utilizing positive-working photoresist. In a further embodiment an alternate fabrication technique is set forth in Figures 17 - 20. This technique has several advantages over the prior technique, primarily due to the function of the etch stop deposited on the reservoir side of the substrate. This feature improves the production of through-wafer channels having a consistent diameter throughout its length. An artifact of the etching process is the difSculty of maintaining consistent channel diameter when approaching an exposed surface of the substrate fi-om within. Typically, the etching process forms a channel having a slightly smaller diameter at the end of the channel as it breaks through the opening. This is unproved by the ability to sUghtly over-etch the channel when contactiDg the etch stop. Further, another advantage of etching the reservoir and depositing an etch stop prior to the channel etch is that micro-protrusions resulting from the side passivation of the channels remaining at the chaimel opening are avoided.. The etch stop also functions to isolate the plasma region from the cooling gas when providing through holes and avoiding possible contamination fi-om etching by products. Figures 17A - 17E and Figures I9A - 19G illustrate the processing steps for the nozzle or ejection side of the substrate in fabricating the electrospray device of the present invention. Figures ISA- ISG illustrate the processing steps for the reservoir or injection side of the substrate in fabricating the electrospray device of the present invention. Figures 20A - 20C illustrate the preparation of the substrate for electrical isolation. Referring to the plan view of Figure 17A, a mask is used to pattern 302 that wiii form the nozzle shape in the completed electrospray device 250. The patterns in the form of circles 304 and 306 fomas through-wafer channels and a recessed annular space around the nozzles, respectively of a completed electrospray device. Figure 17B is the cross-sectional view taken along line I7B-I7B of Figure 17A. A double-side poHshed silicon wafer 300 is subjected to an elevated temperature in an oxidizing environment to grow a layer or film ofsilicon dioxide 310 on the nozzle side and a layer or film ofsilicon dioxide 312 on the reservoir side of the substrate 300. Each of the resulting silicon dioxide layers 310, 312 has a thickness of approximately 1-3 |i,m. The silicon dioxide layers 310, 312 serve as masks for subsequent selective etching of certain areas of the silicon substrate 300. A film of positive-working photoresist 308 is deposited on the silicon dioxide layer 310 on the nozzle side of the substrate 300. Referring to Figure I7C, an area of the photoresist 304 corresponding to the entrance to through-wafer channels and an area of photoresist corresponding to the recessed annular region 306 which will be subsequently etched is selectively exposed through a mask (Figure 17A) by an optical lithographic exposure tool passing short-wavelength light, such as blue or near-ultraviolet at wavelengths of 365, 405, or 436 nanometers. As shown in the cross-sectional view of Figure 17C, after development of the photoresist 308, the exposed area 304 of the photoresist is removed and open to the underlymg siUcon dioxide layer 314 and the exposed area 306 of the photoresist is removed and open to the underlying silicon dioxide layer 310, while the tmexposed areas remain protected by photoresist 308. Referring to Figure 17D, the exposed areas 314, 316 of the silicon dioxide layer 310 is then etched by a fluorine-based plasma with a high degree of anisotropy and selectivity to the protective photoresist 308 until the silicon substrate 318,320 are reached. As shown in the cross-sectional view of Figure 17E, the remaining photoresist 308 is removed &om the silicon substrate 300. Referring to the plan view of Figure 18 A, a mask is used to pattern 324 in the form of a circle. Figure 18B is the cross-sectional view taken along line 18B-18B of Figure 18A. As shown in the cross-sectional view in Figure 18B a film- of positive-working photoresist 326 is deposited on the silicon dioxide layer 312. Patterns on the reservoir side are aligned to those previously formed on the nozzle side of the substrate using through-substrate ahgnments. After alignment, an area of the photoresist 326 corresponding to the circular reservoir 324 is selectively exposed through the mask (Figure ISA) by an optical lithographic exposure tool passing short-wavelength light, such as blue or ■ near-ultraviolet at wavelengths of 365,405, or 436 nanometers. Asshown in the cross-sectional view of Figure 18C, the photoresist 326 is then developed to remove the exposed areas of the photoresist 324 such that the reservoir region is open to the underlying silicon dioxide layer 328, while the imexposed areas remain protected by photoresist 326. The exposed area 328 of the silicon dioxide layer 312 is then etched by a fluorine-based plasma with a high degree of anisotropy and selectivity to the protective photoresist 326 until the silicon substrate 330 is reached as shown in Figure 18D. As shown in Figure 18E, a fluorine-based etch creates a cylindrical region that defines a reservoir 332. The reservoir 332 is etched until the through-wafer chaimel depths are reached. After the desired depth is achieved the remaining photoresist 326 is then removed in an oxygen plasma or in an actively oxidizing chemical bath like sulfiiric acid (H:S04) activated with hydrogen peroxide (H2O2), as shown in Figure 18F. Referring to Figure 18G, a plasma enhanced chemical vapor deposition ("PECVX>") silicon dioxide layer 334 is deposited on the reservok side of the substrate 300 to serve as an etch stop for the subsequent etch of the through substrate channel 336 shown in Figure 19D. A film of positive-working photoresist 308' is deposited on the silicon dioxide layer 310 on the nozzle side of the substrate 300, as shown in Figure 19B. Referring to Figure 19C, an area of the photoresist 304 corresponding to tiie entrance to through-wafer channels is selectively exposed through a mask (Figure 19A) by an optical lithographic exposure tool passing short-wavelength light, such as blue or near-ulCraviolel at wavelengths of 365,405, or 436 nanometers. As shown in the cross-sectional view of Figiu-e 19C, after development of the photoresist 308', the exposed area 304 of the photoresist is removed to the underlying silicon substrate 318. The remaining photoresist 308' is used as a mask during the subsequent fluorine based DRIE silicon etch to vertically etch the through-wafer channels 336 shown in Figure 19D. After etching the tiirough-wafer channels 336, the remaining photoresist 308' is removed from the silicon substrate 300, as shown in the cross-sectional view of Figure 19E. The removal of the photoresist 308' eiqxjses the mask pattern of Figure 17A foraied in the silicon dioxide 310 as shown in Figure 19E. The fluorine based DRJE silicon etch is used to vertically etch the recessed annular region 338 shown in Figure 19F. Referring to Figure 19G, the silicon dioxide layers 310, 312 and 334 are removed from the substrate by a hydrofluoric acid process. An advantage of the fabrication process described herein is that the process simplifies the alignment of the through-wafer channels and the recessed annular region. This allows the fabrication of smaller nozzles with greater ease without any complex aiigrnnenl of masks. Dimensions of the through channel, such as the aspect ratio (i.e. depth to width), can be reliably ^d reproducibiy limited and controUed. Preparation of the Substrate for Electrical Isolation Referring to Figure 20A, the silicon wafer 300 is subjected to an elevated temperature in an oxidizing environment to grow a layer or film of silicon dioxide 342 on all silicon surfaces to a thickness of approximately 1-3 |j.m. The silicon dioxide layer serves as an electrical insulating layer. Silicon nitride 344 is finTher deposited using low pressure chemical vapor deposition (LPCVD) to provide a conformal coating of silicon nitride on all surfaces up to 2 ^m in thickness, as shown in Figure 20B. LPCVD silicon nitride also provides further electrical insulation and a fluid barrier that prevents fluids and ions contained therein that are introduced to the electrospray device from causing an electrical connection between the fluid the silicon substrate 300- This allows for the independent application- of a potential voltage to a fluid and the substrate with this electrospray device to generate the high electric field at the nozzle tip required for successful nanoelectrospray of fluids from microchip devices. After fabrication of multiple electrospray devices on a single silicon wafer, the wafer can be diced or cut into individual devices. This exposes a portion of the silicon substrate 300 as shown in the cross-sectional view of Figure 20C on which a layer of conductive metal 346 is deposited, which serves as the substrate electrode. A layer of conductive metal 348 is deposited on the silicon nitride layer of the reservoir side, which serves as the fluid electrode. All silicon surfaces are oxidized to form silicon dioxide with a thickness that is conttoUable through choice of temperature and time of oxidation. All silicon dioxide surfaces are LPCVD coated with silicon nitride. The fipal thickness of the silicon dioxide and silicon nitride can be selected to provide the desired degree of electrical isolation in the device. A thicker layer of silicon dioxide and silicon nitride provides a greater resistance to electrical breakdown. The silicon substrate is divided into the desired size or array of electrospray devices for purposes ofmetalizationof the edge of the silicon substrate. As shown in Figure 20C, the edge of the silicon substrate 300 is coated with a conductive material 248 using weU known thermal evaporation and metal deposition techniques. The fabrication methods confer superior mechanical stability to the fabricated electrospray device by etching the features of the electrospray device from a monocrystalline silicon substrate without any need for assembly. The alignment scheme allows for nozzle walls of less than 2 fim and nozzle outer diameters down to 5 Jim to be fabricated reproducibly. Further, the lateral extent and shape of the recessed annular region can be controlled independently of its depth. The depth of the recessed annular region also determines the nozzle height and is determined by the extent of etch on the nozzle side of the substrate. Figures 21A and 2 IB show a perspective view of scanning electron micrograph images of a multi-nozzle device fabricated in accordance with the present invention. The nozzles have a 20 (im outer diameter and an 8 \im inner diameter. The pitch, which is the nozzle center to nozzle center spacing of the nozzles is 50 yua. The above described fabrication sequences for the electrospray device can be easily adapted to and are apphcable for the simultaneous fabrication of a single monolithic system comprising multiple electrospray devices including multiple channels and/or multiple ejection nozzles embodied in a single monolithic substrate. Further, the processing steps may be modified to fabricate similar or different electrospray devices merely by, for example, modifying the layout design and/or by changing the polarity of the photomask and utilizing negative-working photoresist rather than utihzing positive-working photoresist. Interface of a Multi-System Chip to a Mass Spectrometer Arrays of electrospray nozzles on a multi-system chip may be interfaced with a sampling orifice of a mass spectrometer by positioning the nozzles near the sampling orifice. The tight configuration of electrospray nozzles allows the positioning thereof in close proximity to the sampling orifice of a mass spectrometer. A multi-system chip may be manipulated relative to the ioi. -mpling orifice to position one or more of the nozzles for electrospray near the sampling orifice. Appropriate voItage(s) may then be applied to the one or more of the nozzles for electrospray. Although the invention has been described in detail for the purpose of illustration, it is understood that such detail is solely for that purpose, and variations can be made therein by those skilled in the art without departing fi^om the spirit and scope of the invention which is defined by the following claims. WE CLAIM: 1. An electrospray device for generating multiple sprays from a single fluid stream comprising: a substrate having: an injection surface; an ejection surface opposing the injection surface, wherein the substrate is an integral monolith having either a plurality of spray units each capable of generating a single electro spray plume wherein the entrance orifice of each spray unit is in fluid communication with one another or a plurality of spray units each capable of generating muhiple electrospray plumes wherein the entrance orifice of each spray unit is in fluid communication with one another or a single spray unit; capable of generating muhiple electrospray plumes; for spraying the fluid, each spray unit comprising: an entrance orifice on the injection surface, an exit orifice on the ejection surface, a channel extending between 'the entrance orifice and the exit orifice, and a recess surrounding the exit orifice positioned between the injection surface and the ejection surface; and an electric field generating source positioned to defme an electric field surrounding at least one exit orifice. 2. The electro spray device as claimed in claim 1, wherein the substrate has a plurality of spray units each capable of generating a single electrospray plume wherein the entrance orifice of each spray unit is in fluid communication with one another. 3. The electrospray device as claimed in claim 1, wherein the substrate has a plurality of spray units each capable of generating multiple electrospray plumes wherein the entrance orifice of each spray unit is in fluid communication with one another. k The electro spray device as claimed in claim 1, wherein the substrate has a single ;pray unit capable of generating multiple electro spray plimies. 5. The electro spray device as claimed in claim 2, wherein the plurality of spray units ire configured to generate a single combined electro spray plume of fluid. 5. The electro spray device as claimed in claim 3, wherein at least one of the spray jnits is configured to generate multiple electro spray plumes of fluid which remain discrete. 7. The electro spray device as claimed in claim 3, wherein the plurality of spray units are configured to generate a single combined electro spray plume of fluid. 8. The electro spray device as claimed in claim 4, wherem the single spray unit is configured to generate multiple electrospray plumes of fluid which remain discrete. 9. The electro spray device as claimed in claim 2, wherein the exit orifices of the spray units are present on the ejection surface at a density of up to 10,000 exit orifices/cm2. 10. The electro spray device as claimed in claim 2, wherein the exit orifices of the spray units are present on the ejection surface at a density of up to 15,625 exit orifices/cm2. 11. The electro spray device as claimed in claim 2, wherein the exit orifices of the spray units are present on the ejection surface at a density of up to 27,566 exit orifices/cm2. 12. The electro spray device as claimed in claim 2, wherein the exit orifices of the spray units are present on the ejection surface at a density of up to 40,000 exit orifices/cm2. 13. The electro spray device as claimed in claim 2, wherein the exit orifices of the spray units are present on the ejection surface at a density of up to 160,000 exit orifices/cm2. 14. The electrospray device as claimed in claim 3, wherein the exit orifices of the spray units are present on the ejection surface at a density of up to 10,000 exit orifices/cm . 15. The electrospray device as claimed in claim 3, wherein the exit orifices of the spray units are present on the ejection surface at a density of up to 15,625 exit orifices/cm2. 16. The electrospray device as claimed in claim 3, wherein the exit orifices of the spray units are present on the ejection surface at a density of up to 27,566 exit orifices/cm2. 17. The electrospray device as claimed in claim 3, wherein the exit orifices of the spray units are present on the ejection surface at a density of up to 40,000 exit orifices/cm2. 18. The electrospray device as claimed in claim 3, wherein the exit orifices of the spray units are present on the ejection surface at a density of up to 160,000 exit orifices/cm2. 19. The electrospray device as claimed in claim 2, wherein the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is less than 500 pm. 20. The electro spray device as claimed in claim 2, wherein the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is less than 200 |im. 21. The electro spray device as claimed in claim 2, wherein the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is less than 100 |mi. 22. The electro spray device as claimed in claim 2, wherein the spacing on the ejection surface between the centers of adjacent exit orifices of the spray imits is less than 50 |jm. 23. The electrospray device as claimed in claun 3, wherein the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is less than 500 ^im. 24. The electro spray device as claimed in claim 3, wherein the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is less than 200 pm. 25. The electro spray device as claimed in claim 3, wherein the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is less than 100 um. 26. The electro spray device as claimed in claun 3, wherein the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is less than 50 um. 27. The electrospray device as claimed in claim 1, wherein said substrate comprises silicon. 28. The electro spray device as claimed in claim 1, wherein said substrate is polymeric. 29. The electrospray device as claimed in claim I, wherein said substrate comprises glass. 30. The electrospray device as claimed in claim 2, wherein said electric field generating source comprises: a first electrode attached to said substrate to impart a first potential to said substrate; and a second electrode to impart a second potential, wherein the first and the second electrodes are positioned to define an electric field surrounding at least one exit orifice. 31. The electro spray device as claimed in claim 30, wherein the first electrode is electrically msulated fi-om the fluid and the second potential is applied to the fluid. 32. The electrospray device as claimed in claim 30, wherein the first electrode is in electrical contact with the fluid and the second electrode is positioned on the ejection surface. 33. The electro spray device as claimed in claim 3, wherein said electric field generating source comprises: a first electrode attached to said substrate to impart a first potential to said substrate; and a second electrode to unpart a second potential, wherein the first and the second electrodes are positioned to define an electric field surrounding at least one exit orifice. 34. The electro spray device as claimed in claim 33, wherein the firet electrode is electrically insulated from the fluid and the second potential is applied to the fluid. 35. The electro spray device as claimed in claim 33, wherein the first electrode is in electrical contact with the fluid and the second electrode is positioned on the ejection surface. 36. The electro spray device as claimed in claim 4, wherein said electric field generating source comprises: a first electrode attached to said substrate to impart a first potential to said substrate; and a second electrode to impart a second potential, wherein the first and the second electrodes are positioned to define an electric field surrounding the exit orifice. 37. The electro spray device as claimed in claim 36, wherein the first electrode is electrically insulated from the fluid and the second potential is applied to the fluid. 38. The electrospray device as claimed in claim 36, wherein the first electrode is in electrical contact with the fluid and the second electrode is positioned on the ejection surface. 39. The electro spray device as clauned m claim 27, wherein said fyst electrode is positioned within 500 microns of the exit orifice. 40. The electrospray device as claimed in claim 27, wherein said first electrode is positioned within 200 microns of the exit orifice. 41. The electro spray device as claimed in claim 27, wherein said second electrode is positioned within 500 microns of the exit orifice. 42. The electrospray device as claimed in claim 27, wherein said second electrode is positioned within 200 microns of the exit orifice. 43. The electro spray device as claimed in claim 27, wherein the exit orifice has a distal end in conductive contact with the substrate, 44. The electrospray device as claimed in claim 33, wherein said first electrode is positioned within 500 microns of the exit orifice. 45. The electrospray device as claimed in claim 33, wherein said first electrode is positioned within 200 microns of the exit orifice. 46. The electrospray device as claimed in claim 33, wherein said second electrode is positioned within 500 microns of the exit orifice. 47. The electrospray device as claimed in claim 33, wherem said second electrode is positioned within 200 microns of the exit orifice. 48. The electro spray device as claimed in claim 33, wherein the exit orifice has a distal end m conductive contact with the substrate. 49. The electro spray device as claimed in claim 36, wherein said first electrode is positioned within 500 microns of the exit orifice. 50. The electrospray device as claimed in claim 36, wherein said first electrode is positioned within 200 microns of the exit orifice. 51. The electro spray device as claimed in claim 36, wherein said second electrode is positione4 within 500 microns of the exit orifice. 52. The electro spray device as claimed in claim 36, wherein said second electrode is positioned within 200 microns of the exit orifice. 53. The electro spray device as claimed in claim 36, wherein the exit orifice has a distal end in conductive contact with the substrate. 54. The electrospray device as claimed in claim 4, wherein the device is configured to permit an electro spray of fluid at a flow rate of up to 2 pL/minute. 55. The electrospray device as claimed in claim 4, wherein the device is configured to permit an electrospray of fluid at a flow rate of from 100 nL/minute to 500 nL/minute. 56. The electro spray device as claimed in claim 2, wherein the device is configured to permit an electrospray of fluid at a flow rate of up to 2 |iL/minute. 57. The electrospray device as claimed in claim 2, wherein the device is configured to permit an electrospray of fluid at a flow rate of greater than 2 loL/minute. 58. The electrospray device as claimed in claim 57, wherein the flow rate is fi-om 2 pL /minute to 1 mL/minute. 59. The electro spray device as claimed in claim 57, wherein (he flow rate is from 100 nL/minute to 500 nL/minute. 60. The electrospray device as claimed in claim 3, wherein the device is configured to permit an electro spray of fluid at a flow rate of up to 2 |xL/minute. 61. The electrospray device as claimed in claim 3, wherein the device is configured to permit an electrospray of fluid at a flow rate of greater than 2 |jL/minute. 62. The electrospray device as claimed in claim 61, wherein the flow rate is from 2 )iL /minute to 1 mL/minute. 63. The electro spray device as claimed in claim 61, wherein the flow rate is from 100 nL/minute to 500 nL/minute. 64. An electrospray system for spraying fluid comprising an array of a pJurality of electrospray devices as claimed in claim 1. 65. The electrospray system as claimed in claim 64, wherein the electrospray device density in the array exceeds 5 devices/cm2. 66. The electro spray system as claimed in claim 64, wherein the electro spray device density in the array exceeds 16 devices/cm . 67. The electro spray system as claimed in claim 64, wherein the electrospray device density in the array exceeds 30 devices/cm2. 68. The electrospray system as claimed in claim 64, wherein the electrospray device density in the array exceeds 81 devices/cm2. 69. The electrospray system as claimed in claim 64, wherein the electrospray device density in the array is from 30 devices/cm2 to 100 devices/cm2. 70. The electro spray system as claimed in claim 64, wherein said array is an integral monolith of said devices. 71. The electro spray system as claimed in claim 64, wherein at least two, of the devices are in fluid communication with different fluid streams. 72. The electrospray system as claimed in claim 64, wherein at least one spray unit is configured to generate multiple electrospray plumes of fluid. 73. The electro spray system as claimed in claim 64, wherein at least one of the electro spray devices is configured to generate a single combined electro spray plume of fluid. 74. The electrospray system as claimed in claim 64, wherein at least one spray unit of the plurality of spray units is configured to generate a single electrospray plume of fluid. 75. The electrospray system as claimed in claim 64, wherein at least one spray unit of the plurality of spray units is configured to generate multiple electrospray plumes of fluid which remain discrete. 76. The electro spray system as claimed in claim 64, wherein said substrate comprises silicon. 77. The electro spray system as claimed in claim 64, wherein said substrate is polymeric. 78. The electrospray system as claimed in claim 64, wherein said substrate comprises glass. 79. The electrospra}' system as claimed in claim 64, wherein at least one device comprises a substrate having a plurality of spray units each capable of generating a single electrospray plume wherein the entrance orifice of each spray unit is in fluid communication with one another. 80. The electro spray system as claimed in claim 64, wherein at least one device comprises a substrate having a plurality of spray units each capable of generating multiple electrospray plumes wherein the entrance orifice of each spray unit is in fluid communication with one another. 81. The electrospray system as claimed in claim 64, wherein at least one device comprises a substrate having a single spray unit capable of generating multiple electrospray plumes. 82. The electrospray system as claimed in claim 79, wherein the plurality of spray units are configured to generate a single combined electrospray plume of fluid. 83. The electrospray system as claimed in claim 80, wherein at least one of the spray units is configured to generate multiple electro spray plumes of fluid which remain discrete. 84. The electrospray system as claimed in claim 80, wherein the plurality of spray units are configured to generate a single combmed electrospray plume of fluid. 85. The electro spray system as claimed in claim 81, wherein the single spray unit is configured to generate multiple electro spray plumes of fluid which remain discrete. 86. The electro spray system as claimed in claim 79, wherein in at least one device the exit orifices of the spray units are present on the ejection surface at a density of up to 10,000 exit orifices/cm2. 87. The electrospray system as claimed in claim 79, wherein in at least one device the exit orifices of the spray units are present on the ejection surface at a density of up to 15,625 exit orifices/cm2. 88. The electro spray system as claimed in claim 79, wherein in at least one device the exit orifices of the spray units are present on the ejection surface at a density of up to 27,566 exit orifices/cm . 89. The electrospray system as claimed in claim 79, wherem m at least one device the exit orifices of the spray units are present on the ejection surface at a density of up to 40,000 exit orifices/cm2. 90. The electro spray system as claimed in claim 79, wherein in at least one device the exk orifices of the spray units are present on the ejection surface at a density of up to 160,000 exit orifices/cm2. 91. The electrospray system as claimed in claim 80, wherein in at least one device the exit orifices of the spray units are present on the ejection surface at a density of up to 10,000 exit orifices/cm2. 92. The electro spray system as claimed in claim 80, wherein in at least one device the exit orifices of the spray units are present on the ejection surface at a density of up to 15,625 exit orifices/cm'^. 93. The electro spray system as claimed in claim 80, wherein in at least one device the exit orifices of the spray units are present on the ejection surface at a density of up to 27,566 exit orifices/cm2. 94. The electrospray system as claimed in claim 80, wherein in at least one device the exit orifices of the spray imits are present on the ejection surface at a density of up to 40,000 exit orifices/cm2. 95. The electrospray system as claimed in claim 80, wherein in at least one device the exit orifices of the spray units are present on the ejection surface at a density of up to 160,000 exit orifices/cml 96. The electrospray system as claimed in claim 79, wherein in at least one device the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is less than 500 fim. 97. The electrospray system as claimed in 80, wherein in at least one device the spacing on the ejection surface between the centers of adjacent exit orifices of the spray imits is less than 200 |im. 98. The electrospray system as claimed in claim 80, wherein in at least one device the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is less than 100 [un. 99. The electrospray system as claimed in claim 79, wherein in at least one device the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is Jess than 50 fim. 100. The electrospray system as claimed in claim 80, wherein in at least one device the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is less than 500 \xm. 101. The electrospray system as claimed in claim 80, wherein in at least one device the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is less than 200 tim. 102. The electro spray system as claimed in claim 80, wherein in at least one device the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is less than 1 00 pm. 103. The electrospray system as claimed in claim 80, wherein in at least one device the spacing on the ejection surface between the centers of adjacent exit orifices of the spray units is less than 50 i^m. 104. The electrospray system as claimed in claim 79, wherein said electric field generating source comprises: a first electrode attached to said substrate to impart a first potential to said substrate; and a second electrode to impart a second potential, wherein the first and the second electrodes are positioned to define an electric field surrounding at least one exit orifice. 105. The electrospray system as claimed in claim 104, wherein the first electrode is electrically insulated from the fluid and the second potential is applied to the fluid. 106. The electro spray system as claimed in claim 104, wherein the first electrode is in electrical contact with the fluid and the second electrode is positioned on the ejection surface. 107. The electrospray system as claimed in claim 104, wherein application of potentials to said first and second electrodes causes the fluid to discharge from at least one exit orifice in the form of an elecfrospray plume. 108. The electro spray system as claimed in claim 80, wherein said electric field generating source comprises: a first electrode attached to said substrate to impart a first potential to said substrate; and a second electrode to impart a second potential, wherein the first and the second electrodes are positioned to define an electric field surrounding at least one exit orifice. 109. The electrospray system as claimed in claim 108, wherein the first electrode is electrically insulated fi-om the fluid and the second potential is applied to the fiuid. 110. The electro spray system as claimed in claim 108, wherein the first electrode is in electrical contact with the fluid and the second electrode is positioned on .the ejection surface. 111. The electro spray system as claimed in claim 108, wherein application of potentials to said first and second electrodes causes the fluid to discharge front at (east one exit orifice in the form of multiple electrospray plumes. 112. The electrospray system as claimed in claim 81, wherein said electric field generating source comprises: a first electrode attached to said substrate to impart a first potential to said substrate; and a second electrode to impart a second potential, wherein the first and the second electrodes are positioned to define an electric field surrounding the exit orifice. 113. The electro spray system as claimed in claim 112, wherein the first electrode is electrically insulated from the fluid and the second potential is applied to the fluid. 114. The electrospray system as claimed in claim 112, wherein the first electrode is in electrical contact with the fluid and the second electrode is positioned on the ejection surface, 115. The electrospray system as claimed in claim 112, wherein application of potentials to said first and second electrodes causes the fluid to discharge from the orifice in the form of multiple electrospray plumes. 116. The electrospray system as claimed in claim 104, wherein said first electrode is positioned within 200 microns of the exit orifice. 117. The electrospray system as claimed in claim 104, wherein said second electrode is positioned within 200 microns of the exit orifice. 118. The electro spray system as claimed in claim 104, wherein the exit orifice has a distal end in conductive contact with the substrate. 119 The electrospray system as claimed in claim 108, wherein said first electrode is positioned within 200 microns of the exit orifice, 120. The electro spray system as claimed in claim 108, wherein said second electrode is positioned withm 200 microns of the exit orifice. 121. The electro spray system as claimed in claim 108, wherein the exit orifice has a distal end in conductive contact with the substrate. 122. The electro spray system as claimed in claim 112, wherein said first electrode is positioned within 200 microns of the exit orifice. 123. The electro spray system as claimed in claim 112, wherein said second electrode is positioned within 200 microns of the exit orifice. 124. The electrospray system as claimed in claim 112, wherein the exit orifice has a distal end in conductive contact with the substrate. 125. The electrospray system as claimed in claim 81, wherein at least one device is configured to permit an electro spray of fluid at a flow rate of up to 2 |jL/minute. 126. The electro spray system as claimed in claim 81, wherein at least one device is configured to permit an electro spray of fluid at a flow rate of from 100 nL/minute to 500 nL/minute. 127. The electrospray system as claimed in claim 79, wherein the device is configured to permit an electrospray of fluid at a flow rate of up to 2 jiL/minute. 128. The electro spray system as claimed in claim 79, wherein the device is configured to permit an electro spray of fluid at a flow rate of greater than 2 |JL /minute. 129. The electro spray system as claimed in claim 128, wherein the flow rate is from 2 |iL/minute to mL/minute. 130. The electrospray system as claimed in claun 128, wherein the flow rate is from 100 nL/minute to 500 nL/minute. 131. The electro spray system as claimed in claim 80, wherein at least one device is configured to permit an electro spray of fluid at a flow rate of up to 2 |iL/minute. 132. The electro spray system as claimed in claim 80, wherein at least one device is configured to permit an electrospray of fluid at a flow rate of greater than 2 ^iL/minute. 133. The electro spray system as claimed in claim 132, wherein the flow rate is from 2 p,L/minute to 1 mL/mmute. 134. The electrospray system as claimed in claim 132, wherein the flow rate is from 100 nL/minute to 500 nL/minute. 135. The electrospray system as claimed in claim 64, wherein the spacing on the ejection surface between adjacent devices is 9 mm or less. 136. The electrospray system as claimed in claim 64, wherem the spacing on the ejection surface between adjacent devices is 4.5 mm or less. 137. The electrospray system as claimed in claim 64, wherein the spacing on the ejection surface between adjacent devices is 2.2 mm or less. 138. The electrospray system as claimed in claim 64, wherein the spacing on the ejection surface between adjacent devices is 1.1 mm or less. 139. The electrospray system as claimed in claim 64, wherein the spacing on the ejection surface between adjacent devices is 0.56 mm or less. 140. The electro spray system as claimed in claim 64, wherein the spacing on the ejection surface between adjacent devices is 0.28 mm or less. 141. The electro spray system as claimed in claim 79, wherein the spacing on the ejection surface between adjacent devices is 9 mm or less. 142. The electro spray system as claimed in claim 79, wherein the spacing on the ejection surface between adjacent devices is 4.5 mm or less. 143. The electro spray system as claimed in claim 79, wherein the spacing on the ejection surface between adjacent devices is 2.2 mm or less. 144. The electro spray system as claimed m claim 79, wherein the spacing on the ejection surface between adjacent devices is 1.1 mm or less. 145. The electrospray system as claimed in claim 79, wherein the spacing on the ejection surface between adjacent devices is 0.56 mm or less. 146. The electro spray system as claimed in claim 79, wherein the spacing on the ejection smface between adjacent devices is 0.28 mm or less. 147. The electrospray system as claimed in claim 80, wherein the spacing on the ejection smface between adjacent devices is 9 mm or less. 148. The electrospray system as claimed in claim 80, wherein the spacing on the ejection surface between adjacent devices is 4.5 mm or less. 149. The electro spray system as claimed in claim 80, wherein the spacing on the ejection smface between adjacent devices is 2.2 mm or less. 150. The electro spray system as claimed in claun 80, wherein the spacing on the ejection surface between adjacent devices is 1.1 mm or less. 151. The electro spray system as claimed in claim 80, wherein the spacing on the ejection surface between adjacent devices is 0.56 mm or less. 152. The electro spray system as claimed in claim 80, wherein the spacmg on the ejection surface between adjacent devices is 0.28 mm or less. 153. The electrospray system as claimed in claim 81> wherein the spacing Jon the ejection surface between adjacent devices is 9 mm or less. 154. The electrospray system as claimed in claim 81, wherein the spacmg on the ejection surface between adjacent devices is 4.5 mm or less. 155. The electro spray system as claimed in claim 81, wherein the spacing on the ejection surface between adjacent devices is 2.2 mm or less. 156. The electrospray system as claimed in claim 81, wherein the spacing on the ejection surface between adjacent devices is 1.1 mm or less. 157. The electro spray system as claimed in claim 81, wherein the spacing on the ejection surface between adjacent devices is 0.56 mm or less. 158. The electrospray system as claimed in claim 81, wherein the spacing on the ejection surface between adjacent devices is 0.28 mm or less. 159. A system for processing multiple sprays of fluid comprising an electrospray device as claimed in claim 1 and a device to receive multiple sprays of fluid from said electrospray device. 160. The system as claimed in claim 159, wherein the device to receive multiple sprays of fluid receives electro spray plumes of the fluid emanating from a plurality of the spray units of said electrospray device. 161. The system as claimed in claim 160, wherein multiple electrospray plumes of the fluid emanate from at least one of the plurality of spray units of said electrospray device. 162. The system as claimed in claim 159, wherein the device to receive multiple sprays of fluid receives multiple electro spray plumes of the fluid emanating from the single spray unit of said electrospray device. 163. The system as claimed in claim 159, wherein the device to receive multiple sprays of fluid receives droplets of the fluid emanating from a plurality of spray units of said electro spray device, 164. The system as claimed in claim 159, wherein said device to receive multiple sprays of fluid comprises a surface for receiving said fluid. 165. The system as claimed in claim 164, wherein said surface comprises a daughter plate or MALDI sample plate, having a plurality of fluid receiving wells each positioned to receive fluid ejected from said electrospray device. 166. The system as claimed in claim 159, wherein said device to receive multiple sprays of fluid is a mass spectrometry device. 167. The system for processing multiple sprays of fluid comprising: an electrospray system as claimed in claim 64 and a device to receive multiple sprays of fluid from said electro spray system. 168. The system as claimed in claim 167, wherein the device to receive multiple sprays of fluid receives electrospray plumes of the fluid emanating from a plurality of the spray imits of said electrospray system. 59. The system as claimed in claim 168, wherein multiple electrospmy plumes of the uid emanate from at least one of the spray units of said electrospray system. 70. The system as claimed in claim 167, wherein the device to receive multiple 3rays of fluid receives droplets of the fluid emanating from a plurality of spray units f said electrospray system. 71. The system as claimed in claim 167, wherein said device to receive multiple prays of fluid comprises a surface for receiving said fluid. 72. The system as claimed in claim 171, wherein said surface comprises: a daughter plate or MALDI sample plate, having a plurality of fluid receiving rells each positioned to receive fluid ejected from said electrospray system. 73. The system as claimed in claim 167, wherein said device to receive multiple prays of fluid is a mass spectrometry device. 74. A system for processing multiple sprays of fluid comprising: an electrospray device as claimed in claim 1 and a device to provide at least one sample in solution or fluid or combination hereof to at least one entrance orifice of said electrospray device. 175. The system as claimed in claim 174, wherem at least one of: the entrance orifices of the plurali^ of spray units of said electrospray device are in fluid communication with one another by a first reservoir, and the entrance orifice of the single spray unit is in fluid communication with a second reservoir; and wherein said device to provide at least one sample in solution or fluid or combination thereof to at least one entrance orifice comprises: at least one conduit to provide delivery of at least one sample in solution or fluid or combination thereof to at least one reservoir of said device. 176. The system as claimed in claim 177, wherein said at least one conduit comprises a capillary, micropipette, or microchip. 177. The system as claimed in claim 174, wherem the at least one conduit and reservoir provide a fluid tight seal therebetween, said at least one conduit optionally comprising a disposable tip. 178. The system as claimed in claim 174, wherein said at least one conduit is compatible with multiple entrance orifices and is repositionable from one entrance orifice to another enfrance orifice. 179. The system as claimed in claim 178, wherein said at least one conduit is capable of being receded from one entrance orifice and repositioned in line with another entrance orifice and placed in sealing engagement with the another entrance orifice to provide fluid hereto. 180. The system as claimed in claim 174, wherein said device to provide at least one sample in solution or fluid or combination thereof to at least one entrance orifice of said electrospray device carries out liquid separation analysis on the fluid. 181. The system as claimed in claim 180, wherein the liquid separation analysis is capillary electrophoresis, capillary dielectrophoresis, capillary electrochromatography, or liquid chromatography. 182. A system for processing muhiple sprays of fluid comprising: a system as claimed in claim 174 and a device to receive multiple sprays of fluid from said electrospray device. 183. The system as claimed in claim 182, wherein the device to receive multiple sprays of fluid receives plumes of the fluid emanating from a plurality of the spray units of said electro spray device. 184. The system as claimed in claim 182, wherein the device to receive multiple sprays of fluid receives multiple electro spray plumes of the fluid emanating from at least one spray unit of said electrospray device 185. The system as claimed in claim 182, wherein said device to receive multiple sprays of fluid comprises a surface for receiving said fluid. 186. The system as claimed in claim 185, wherein said surface comprises: a daughter plate or MALDI sample plate, having a plurality of fluid receiving wells each positioned to receive fluid ejected from said electrospray system, 187. The system as claimed in claim 182, wherein said device to receive multiple sprays of fluid is a mass spectrometry device. 188. A system for processing multiple sprays of fluid comprising: an electro spray system as claimed in claim 64 and a device to provide at least one sample in solution or fluid or combination thereof to at least one entrance orifice of said electrospray system. 189. The system as claimed in claim 188, wherein at least one of: the entrance orifices of the plurality of spray units of said electrospray device are in fluid communication with one another by a first reservoir, and the entrance orifice of the single spray unit is In fluid communication with a second reservoir; and wherein said device to provide at least one sample in solution or fluid or combination thereof to at least one entrance orifice comprises: at least one conduit to provide delivery of at least one sample in solution or fluid or combination thereof to at least one reservoir of said device. 190. The system as claimed in claim 188, wherein said at least one conduit comprises a capillary, micropipette, or microchip. 191. The system as claimed in claim 188, wherein the at least one conduit and reservoir provide a fluid tight seal therebetween, said at least one conduit optionally, comprising a disposable tip. 192. The system as claimed in claim 188, wherein said at least one conduit is compatible with multiple entrance orifices and is repositionable from one entrance orifice to another entrance orifice. 193. The system as claimed in claim 192, wherem said at least one conduit is capable of being receded from one entrance orifice and repositioned in line with another entrance orifice and placed in sealing engagement with the another entrance orifice to provide fluid thereto. 194. The system as claimed in claim 188, wherein said device to provide at least one sample in solution or fluid or combination thereof to at least one entrance orifice of said electro spray device carries out liquid separation analysis on the fluid. 195. The system as claimed in claim 194, wherein the liquid separation analysis is capillary electrophoresis, capillary dielectrophoresis, capillary electrochromatography, or liquid chromatography. 196. A system for processing multiple sprays of fluid comprising: a system as claimed in claim 188 and a device to receive multiple sprays of fluid from said electrospray system. 197. The system as claimed in claim 196, wherein the device to receive multiple sprays of fluid receives plumes of the fluid emanating from a plurality of the spray units of said electrospray system. 198. The system as claimed in claim 196, wherein the device to receive multiple sprays of fluid receives multiple electro spray plumes of the fluid emanating from at least one spray unit of said electrospray system. 199. The system as claimed in claim 196, wherein said device to receive multiple sprays of fluid comprises a surface for receiving said fluid. 200. The system as claimed in claim 199, wherein said surface comprises: a daughter plate or MALDI sample plate, having a plurality of fluid receiving wells each positioned to receive fluid ejected from said electrospray system. 201. The system as claimed in claim 196, wherein said device to receive multiple sprays of fluid is a mass spectrometry device. 202. A method for processing multiple sprays of fluid comprising: providing an electrospray device as claimed in claim 1; providing a device to provide at least one fluid sample to at least one entrance orifice of said electro spray device; providing a device to receive multiple sprays of fluid or droplets from said electro spray device; passing a fluid from said fluid providing device to said electro spray device; generating an electric filed surrounding the exit orifice of said at least one spray unit such that fluid discharged therefrom forms an electro spray or droplets; and passing said electro spray or droplets from said electrospray device to said receiving device. 203. The method as claimed in claim 202, comprising using said receiving device for performing mass spectrometry analysis, liquid chromatography analysis, or protein, DNA, or RNA combinatorial chemistry analysis, 204. A method for processing multiple sprays of fluid comprising: providing an electrospray system as claimed in claim 64; providing a device to provide at least one fluid sample to at least one entrance orifice of at least one electrospray device of said electrospray system; providing a device to receive multiple sprays of fluid or droplets from said at least one electrospray device; passing a fluid from said fluid providing device to said at least one electrospray device; generating an electric filed surrounding an exit orifice of at least one spray unit within said at least one electrospray device such that fluid discharged therefrom forms an electrospray or droplets; and passing said electrospray or droplets from said at least one electrospray device to said receiving device. 205. The method as claimed in claim 204, comprising using said receiving device for performing mass spectrometry analysis, liquid chromatography analysis, or protein, DNA, or RNA combinatorial chemistry analysis. 206. A method of generating an electro spray comprismg: providing an electro spray device as claimed in claim 1; passing a fluid into the entrance orifice, through the channel, and through the exit orifice of at least one spray unit; generating an electric field sunounding the exit orifice of said at least one spray unit such that fluid discharged therefrom forms an electrospray. 207. The method as claimed in claim 206, comprising: detecting components of the electrospray by spectroscopic detection. 208. The method as claimed in claim 207, wherein the spectroscopic detection is selected from the group consisting of UV absorbance, laser induced fluorescence, and evaporative light scattering. 209. The method as claimed in claim 206, wherein the fluid is discharged at a flow rate of up to 2 [iL/minute. 210. The method as claimed in claim 209, wherein the fluid is discharged at a flow rate of greater than 2 nL /minute. 211. The method as claimed in claim 206, wherein the fluid is discharged at a flow rate of from 2 ^iL/minute to I mL/minute. 212. The method as claimed in claim 206, wherein the fluid is discharged at a flow rate of from 100 nL/minute to 500 nL/minute. 213. A method of mass spectrometric analysis comprising: providing the system as claimed in claim 159, wherein the device to receive multiple sprays of fluid from said electrospray device is a mass spectrometer; passing a fluid into the entrance orifice, through the channel, and through the exit orifice of at least one spray unit under conditions effective to produce an electro spray; and passing the electrospray into the mass spectrometer, whereby the fluid is subjected to a mass spectrometry analysis. 214. The method as claimed in claim 213, wherein the mass spectrometry analysis is selected from the group consisting of atmospheric pressure ionization and laser desorption ionization. 215. A method of liquid chromatographic analysis comprising: providing the system as claimed in claim 174, wherein the device to provide at least one sample in solution or fluid or combination thereof to at least one entrance orifice of said electrospray device is a liquid chromatography device; passing a fluid through the liquid chromatography device so that the fluid is subjected to liquid chromatographic separation; and passing a fluid into the entrance orifice, through the channel, and through the exit orifice of at least one spray unit under conditions effective to produce an electrospray. 216. A method of mass spectrometric analysis comprising: providing the system as claimed in claim 178, wherein the device to receive multiple sprays of fluid from said electro spray device is a mass spectrometer and the device to provide at least one sample in solution or fluid or combination thereof to at least one entrance orifice of said electrospray device is a liquid chromatography device; passing a fluid through the liquid chromatography device so that the fluid Is subjected to liquid chromatographic separation; passing a fluid into the entrance orifice, through the channel, and through the exit orifice of at least one spray unit under conditions effective to produce an electrospray; and passing the electrospray into the mass spectrometer, whereby the fluid is subjected to a mass spectrometry analysis. 217. A method of generating an electro spray comprising; providing an electro spray system as claimed in claim 64; passing a fluid into the entrance orifice, through the channel, and through the exit orifice of at least one spray unit; generating an electric field surrounding the exit orifice such that fluid discharged from the exit orifice of said at least one spray unit forms an electrospray. 218. The method as claimed in claim 217, comprismg: detecting components of the electrospray by spectroscopic detection. 219. The method as ciaimed in claim 218, wherein the spectroscopic detection is selected from the group consisting of UV absorbance, laser induced fluorescence, and evaporative light scattering. 220. The method as claimed in claim 217, wherein the fluid is discharged at a flow rate of up to 2 |iL/minute. 221. The method as claimed in claim 217, wherein the fluid is discharged at a flow rate of greater than 2 pL/minute.. 222. The method as claimed in claim 217, wherein the fluid is discharged at a flow rate of from 2 ^L/minute to 1 mL/minute. 223. The method as claimed in claim 217, wherein the fluid is discharged at a flow rate of from 100 nL/minute to 500 nL/minute. 224. A method of mass spectrometric analysis comprising: providing the system as claimed in claim 167, wherein the device to receive multiple sprays of fluid from said electrospray device is a mass spectrometer; passing a fluid into the entrance orifice, through the channel, and through the exit orifice of at least one spray unit under conditions effective to produce an electro spray; and passing the electro spray into the mass spectrometer, whereby the fluid is subjected to a mass spectrometry analysis. 225. The method as claimed in claim 224, wherein the mass spectrometry analysis is selected from the group consisting of atmospheric pressure ionization and laser desorption ionization. 226. A method of liquid chromatographic analysis comprising: providing the system as claimed in claim 188, wherein the device to provide at least one sample in solution, or fluid or combination thereof to at least one entrance orifice of said electrospray system is a liquid chromatography device; passing a fluid through the liquid chromatography device so that the fluid is subjected to liquid chromatographic separation; and passing a fluid into the entrance orifice, through the channel, and through the exit orifice of at least one spray unit under conditions effective to produce an electrospray. 227. A method of mass spectrometric analysis comprising: providing the system as claimed in claim 192, wherein the device to receive multiple sprays of fluid fi-om said electrospray system is a mass spectrometer and the device to provide at least one sample in solution or fluid or combination thereof to at least one entrance orifice of said electro spray system is a liquid chromatography device; passing a fluid through the liquid chromatography device so that the fluid is subjected to liquid chromatographic separation; passing a fluid into the entrance orifice, through the channel, and through the exit orifice of at least one spray unit under conditions effective to produce an electrospray; and passing the electrospray into the mass spectrometer, whereby the fluid is subjected to a mass spectrometry analysis. 228. A method of generating multiple sprays irom a single fluid stream of an electro spray device comprising: providing an electrospray device for spraying a fluid comprising; a substrate having an injection surface; an ejection surface opposing the injection surface, wherein the substrate is an integral monolith having a plurality of spray imits wherein entrance orifices of each spray unit are in fluid communication with one another, each spray unit comprising: an entrance orifice on the injection surface, an exit orifice on the ejection surface, a channel extending between the entrance orifice and the exit orifice, and a recess surrounding the exit orifice positioned between the injection surface and the ejection surface; and an electric field generating source positioned to define an electric field surrounding each exit orifice, wherein each spray unit generates at least one plume of the fluid capable of overlapping with that emanating from other spray units of said electro spray device; depositing on the injection surface analyte from a fluid sample; eluting the analyte deposited on the injection surface with an eluting fluid; passing the eluting fluid containing analyte into the entrance orifice, through the channel, and through the exit orifice of each spray tmit; generating an electric field surrounding the exit orifice such that fluid discharged from the exit orifice of each of the spray units forms an electrospray 229. The method as claimed in claim 228, wherem said deposhing on the injection surface comprises: contacting the fluid sample with the injection surface and evaporating the fluid sample under conditions effective to deposit the analyte on the injection surface. 230. The method as claimed in claim 228, wherein the substrate for said electro spray device has a plurality of spray units for spraying the fluid. 231. The method as claimed in claim 228, wherein the fluid is discharged at a flow rate of up to 2 pL/minute, 232. The method according to claim 228, wherein the fluid is discharged at a flow rate of greater than 2 pL/minute. 233. The method as claimed in claim 228, wherein the fluid is discharged at a flow rate of from 2 pL/minute to 1 mL/minute. 234. The method as claimed in claim 228, wherein the fluid is discharged at a flow rate of from 100 nL/minute to 500 nL/minute. 235. A method of mass spectrometric analysis comprismg: providing a mass spectrometer and passing the eJectrospray produced by the method as claimed in claim 228 into the mass spectrometer, whereby the fluid is subjected to a mass spectrometry analysis. 236. The method as claimed in claim 228, wherein the mass spectrometry analysis is selected from the group consisting of atmospheric pressure ionization and laser desorption ionization, 237. A method of producing an electrospray device comprising: providing a substrate havine onoosed first and second surfaces, the first side coated with a photoresist over an etch-resistant material; exposing the photoresist on the first surface to an image to form a pattern in the form of at least one ring on the first surface; removing the exposed photoresist on the first surface which is outside and inside the at least one ring leaving the unexposed photoresist; removing the etch-resistant material from the first surface of the substrate where the exposed photoresist was removed to form holes in the etch-resistant material; optionally, removing all photoresist remaining on the first surface; coating the first surface with a second coating of photoresist; exposing the second coating of photoresist within the at least one ring to an image; removing the exposed second coating of photoresist from within the at least one ring to form at least one hole; removing material from the substrate coincident with the at least one hole in the second layer of photoresist on the first surface to form at least one passage extending through the second layer of photoresist on the first surface and into substrate; optionally removing all photoresist from the first surface; applying an etch-resistant layer to all exposed surfaces on the first surface side of the substrate; removing the etch-resistant layer from the first surface that is around the at least one rmg; removing material from the substrate exposed by the removed etch- resistant layer around the at least one ring to defme at least one nozzle on the first surface; providing a photoresist over an etch-resistant material on the second surface; exposing the photoresist on the second surface to an image to form a pattern circumscribing extensions of the at least one hole formed in the etch-resistant material of the first surface; removing the exposed photoresist on the second surface; removing the etch-resistant material on the second surface coincident with where the photoresist was removed; removing material from the substrate comcident with where the etch-resistant material on the second surface was removed to form a reservoir extending into the substrate to the extent needed to join the reservoir and the at least one passage; and applying an etch-resistant material to all surfaces of the substrate to form the electro spray device. 238. The method as claimed in claim 237, wherein the substrate is made from silicon and the etch-resistant material is silicon dioxide. 239. The method as claimed in claim 237 comprising: applying a silicon nitride layer over all surfaces after said applying an etch-resistant material to all exposed surfaces of the substrate. 240. The method as claimed in claim 239 comprising: applying a conductive material to a desired area of the substrate. 241. A method of producing an electro spray device comprising: providing a substrate having opposed first and second surfaces, the first side coated with a photoresist over an etch-resistant material; exposing the photoresist on the first surface to an image to form a pattern in the form of at least one ring on the first surface; removing the exposed photoresist on the first surface which is outside and inside the at least one ring leaving the unexposed photoresist; removing the etch-resistant material from the first surface of the substrate where the exposed photoresist was removed to form holes in the etch-resistant material; optionally, removing all photoresist remaining on the first surface; providing a photoresist over an etch-resistant material on the second surface; exposing the photoresist on the second surface to an image to form a pattern circumscribing extensions of the at least one ring formed in the etch-resistant material of the first surface; removing the exposed photoresist on the second surface; removing the etch-resistant material on the second surface coincident with where the photoresist was removed; removing material from the substrate coincident with where the etch-resistant material on the second surface was removed to form a reservoir extending into the substrate; and optionally removing the remaining photoresist on the second surface; coating the second surface with an etch-resistant material; coating the first surface with a second coating of photoresist; exposing the second coating of photoresist within the at least one ring to an image; removing the exposed second coating of photoresist from within the at least one ring to form at least one hole; removing material from the substrate coincident with the at least one hole in the second layer of photoresist on the first surface to form at least one passage extending through the second layer of photoresist on the first surface and into substrate to the extent needed to reach the etch-resistant material coating the reservoir; removing at least the photoresist around the at least one ring from the first surface; removing material from the substrate exposed by the removed etch-resistant layer around the at least one ring to define at least one nozzle on the first surface; removing from the substrate at least the etch-resistant material coating the reservoir; and applying an etch resistant material to coat all exposed surfaces of the substrate to form the electrospray device. 242. The method as claimed in claun 24 i, wherein the substrate is made from silicon and the etch-resistant material is silicon dioxide. 243. The method as claimed in claim 241 comprising: applying a silicon nitride layer over all surfaces after said applying an etch-resistant material to all exposed surfaces of the subsfrate. 244. The method as claimed in claim 243 comprising: applying a conductive material to a desired area of the substrate. 245. A method for producing larger, minimally-charged droplets from a device, comprising: providing the electrospray device as claimed in claim 2; passing a fluid into at least one entrance orifice, through the channel, and through the exit orifice of at least one spray unit of said electrospray device; and generating an electric field surrounding the exit orifice to a value less than that required to generate an electro spray of said fluid. 246. The method as claimed in claim 245, wherein the fluid to substrate potential voltage ratio is less than 2. 247. A method for producing larger, minimally-charged droplets from a device, comprising: providing the electrospray system as claimed in claim 64; passing a fluid into at least one entrance orifice, through the channel, and through the exit orifice of at least one spray unit of at least one electro spray device; and generating an electric field surrounding the exit orifice to a value less than that required to generate an electrospray of said fluid. 248. The method as claimed in claim 247, wherein the fluid to substrate potential voltage ratio is less than 2.

Documents:

in-pct-2002-1001-che abstract.pdf

in-pct-2002-1001-che assignment.pdf

in-pct-2002-1001-che claims.pdf

in-pct-2002-1001-che correspondecne others.pdf

in-pct-2002-1001-che correspondecne po.pdf

in-pct-2002-1001-che description (complete).pdf

in-pct-2002-1001-che drawings.pdf

in-pct-2002-1001-che form-1.pdf

in-pct-2002-1001-che form-19.pdf

in-pct-2002-1001-che form-26.pdf

in-pct-2002-1001-che form-3.pdf

in-pct-2002-1001-che form-5.pdf

in-pct-2002-1001-che others document.pdf

in-pct-2002-1001-che others.pdf

in-pct-2002-1001-che pct.pdf

in-pct-2002-1001-che petition.pdf

in-pct-2002-1001-che.tif