Title of Invention	A MICRODOSING APPARATUS AND METHOD FOR DISPENSING DESIRED VOLUME OF LIQUIDS
Abstract	The invention relates to a microdosing apparatus, comprising a fluid conduit (100; 150) having a flexible tube with a first end (102) for connecting to a liquid reservoir (200) and a second end where an outlet opening (10) is located; and an actuating device having a displacer (108; 108'; 208; 306; 316) with adjustable hub, by which the volume of a portion of the flexible tube can be changed, to thereby dispense liquid as free flying droplets or as free flying jet at the outlet opening (104) by moving the displacer (108; 108'208; 306; 316) between a first end position and a second end position, wherein the tube is partly compressed at least in the first end position or the second end position.

Title of Invention

A MICRODOSING APPARATUS AND METHOD FOR DISPENSING DESIRED VOLUME OF LIQUIDS

Abstract

The invention relates to a microdosing apparatus, comprising a fluid conduit (100; 150) having a flexible tube with a first end (102) for connecting to a liquid reservoir (200) and a second end where an outlet opening (10) is located; and an actuating device having a displacer (108; 108'; 208; 306; 316) with adjustable hub, by which the volume of a portion of the flexible tube can be changed, to thereby dispense liquid as free flying droplets or as free flying jet at the outlet opening (104) by moving the displacer (108; 108'208; 306; 316) between a first end position and a second end position, wherein the tube is partly compressed at least in the first end position or the second end position.

Full Text	Description The present invention relates to a microdosing apparatus, to methods for dosed dispensing of liquids and to methods tor adjusting a desired dosing volume range when using an incentive microdos ing apparatus. According to the prior art, volumes in the nanoliter range require specific methods to ensure the required precision. Here, in addition to contact methods, conventional dispensing methods, pin printing methods, etc., contactless methods are of significant importance. A class of known methods is based on fast-switching valves. Therefore, a suitable valve, mostly based on magnetic or piezoelectrical drives, is connected to a media reservoir via a conduit and pressure is built up in the same. By the than 1 ms, a very large flow is generated for a short term, so that the fluid, even with high surface tensions, can separate from the dispensing position and can impinge on the substrate as free jet. The closing amount can be controlled by the pressure and/or the switchinq time of the valve. Different approaches exist for generating the pressure, there are in the above-described concept with switched valves. A schematic representation showing a first known approach, which can be referred to as syringe solenoid method, is shown in Fig. 7. Here, a fluid conduit 10 is fluidically connected to a syringe 14, which can be removable, via a fast-switching microsolenoid valve 12. At the lower end of the syringe 14, there is a nozzle opening 16. The opposite end of the fluid conduit 10 is connected to a syringe pump 20 via a switching valve 18. Further, a fluid reservoir 22 is also connected to the switching valve 18 via a further f1uid conduit 24. The switching valve 18 has two switching states. In a first switching state, a pump chamber 26 of the syringe pump 20 is fluidically connected to the fluid reservoir 22 via the fluid conduit 24, so that liquid 28 can be drawn from the fluid reservoir into the pump chamber 26, by increasing the volume of the pump chamber 26 by a corresponding movement of the piston 30 of the syringe pump. This process serves process, the switching valve 13 is switched to effect a fluidic connection of the pump chamber 2 6 to the microsolenoid valve 12 via the fluid conduit 10. By using the piston 30, pressure is applied to the liquid inside the pump chamber 26, so that by fast switching the microsolenoid valve 12 switching time 1 mi, liquid can Dosing apparatuses of the type shown in Fig. 7 are, for example, sold by the company Cartesian. An alternative principle, as is practiced, for example, by the companies Delo and Vermes, is shown in Fig. 8. In this alternative method, a pressure container 40 is provided, containing liquid 42 under pressure. An outlet of the pressure container 40 is connected to a quickly switchable valve 46 via a fluid conduit 44, which is again connected to a nozzle opening, shown merely schematically as arrow in Fig. 8, via a fluid conduit 48. In this arrangement, liquid can also be dispensed in a free jet from the nozzle opening by fast switching of the valve 46. described in DE.-A- 1 9-02 36" , DF-A-19802368 and EP-A-0725267. The microdOSinq apparatuses described there comprise a pump chamber abutting to a flexible membrane and connected to a reservoir "ia a supply line and to a nozzle opening via a drain. An example for such a microdosing apparatus will be discussed below with reference to Figs. 9a - 9c. microdosing apparatus in the resting position is shown. The dosing apparatus comprises a dosing head 50 and an actuating 'device 52. In the shown example, the dosing head 50 is formed by two interconnected substrates 54, 56, in which respective recesses are formed. The first substrate 5-1 is structured such that a reservoir connection 58, an inlet channel 60 and a dosing chamber 62 are formed in the same. The lower substrate 56 is structured such that a nozzle connection 6-1, a nozzle 66 having a nozzle channel and an outlet opening, and an outlet area 68 having a significantly larger cross section than the outlet opening Further, a membrane 64 is formed the upper substrate 54 by the structuring of the same. The actuating device 52 has a displacer 72, by which the membrane can be deflected downwards to reduce the volume of the dosing chamber 62, as shown in Fig. 9b. By this reduction oi the volume or the dosing chamber z, on the one hand, a backflow 74 results through the inlet channel 60 and the reservoir connection 58. On the other hand, a forward flow results through the nozzle connection 64 and the nozzle 66, so that dispensing liquid 76 takes place at the outlet end of the nozzle 66. The ratio between backflow 74 and dosed liquid 76 depends on the ratio of flow resistance of fluid connection between reservoir and dosing chamber to the flow resistance between dosing chamber and outlet opening of the nozzle 66. Alter the dosing process, the displacer 72 is moved upwards by using the actuating device 52, see Fig. 9c, so that the same finally resumes its original position by elasticity, as shown in Fig. 9a. By this resetting of the membrane 70, an increase of the volume of the dosing chamber 62 results, so that a refill flow 78 from the reservoir through the reservoir connection 58 and the inlet channel 60 occurs. In order to avoid an intake of air through the nozzle 66 during this phase, resetting the membrane 70 has to be performed slowly enough, so that capillary forces keeping the liquid in nozzle 66 are not overcome thereby. Microdosing apparatuses as described above with reference to Figs. 9a - 9c have originally been developed for enzyme dosage in biochemistry. By using these apparatuses, liquids with viscosities up to 100 mPas in a volume range of 1 nL to 1000 nL can be dosed very media independent and precisely. The liquid to be dosed is thereby dosed by displacing a dosing chip, preferably made of silicon, in free jet from the dosing chamber, which is. However, this method requires a comparatively complex micro device. Finally, a droplet ejection system is known from U.S 3,683,212, wherein a tube shaped piezoconverter connects a fluid conduit to a nozzle plate wherein a nozzle opening is formed. A voltage pulse with short rise time is applied to the converter to effect contraction of the converter. The resulting sudden decrease of the enclosed volume causes a small amount of fluid to be ejected from the opening in the opening plate. Thereby, the liquid is kept under no or no low pressure. The surface tension at the opening prevents that liquid flows out when the converter is not operated. The ejected liquid is replaced by a capillary forward flow of liquid in the conduit. It has been found out that according to US- 3 , 683,212, the drop is generated with the help of an acoustic principle similar to the piezoelectric inkjet methods. Here, an acoustic pressure wave is generated in a rigid fluid conduit, for example a rigid glass capillary, which results in a high pressure gradient locally at an output position, which leads to drop separation. The actuating time of the actuator iS here in the range of the sound propagation in the system, which is normally several microseconds. Thus, in this context, the acoustic impedance of the fluid conduits below and above the actuator is of significance for the design. Thus, this is an impulse method where a high acoustic impulse is generated with a low volume displacement. In other words, a sound wave with pressure maxima and pressure minima is generated between the actuation position and the disposing position, wherein ejection of liquid is effected at the dispensing position by a corresponding pressure. According to US 3,683,212, the fluid conduct is only negligibly deformed, the actuator mainly only transmits sound and the elasticity of the fluid conduit has no significant importance. From DE 4 313 C2, an apparatus for dosing liquids is known, having a liquid supply tube connected if one end a liquid reservoir and open at the other end. The tube is applied to an abutment socket and a hammer is provided on the side opposing the abutment socket of the tube. The hammer can vibrated periodically in a direction transversal to the tube axis, so that the whole tube cross section is crimped by the hammer, i.e. the flow area is substantially brought to zero. Therebv, impulsive force impact's are exerted on the tube and individual liquid drops are driven out of the open end. Tt is the ohiect of the present invention to provide a microdosing apparatus with a simple structure, which further preferably allows an easy change of a dosing volume to be dispensed. It is a further object of the present invention to provide a method for dosed dispensing of liquids. This object is achieved by microdosing apparatuses according to claims 1 and 9 and a method according to claim 20, 29 and 30 . The present nvention provides a microdosing apparatus comprising: a fluid conduit having a flexible tube, preferably a polymer tube, with a first end for connecting to a liquid reservoir and a second end where an output opening is located; and an actuating device having a displacer with adjustable hub, by which the volume of a portion of the flexible tube can be changed, to thereby dispense liquid as free flying droplets or as free flying jet at the outlet opening by moving the displacer between the first end position and the second end position, wherein the tube is partly compressed at least in the first end position or the second end position. Further, the present invention provides a microdosing apparatus, comprising: reservoir and a second end where an outlet opening is located, the fluid conduit having a portion along which a cross section of the fluid conduit can be varied to effect a change of the volume of the fluid conduit; portion of the fluid conduit for effecting a change of the volume oi the fluid conduit to thereby dispense liquid as free flyiny droplets or free flying jet from the outlet opening; wherein a ratio of the fluidic impedance between the position of the actuating device and the outlet opening to a fluidic impedance between the fluid reservoir and the position of the actuating device is variable by changing the position of the actuating device, so that a dosing volume dispensed at the outlet opening is variable by at least 10 Here, impedance means the combination oi fluidic resistance and fluidic inductance determined by the length and the flow cross section of a line. Thus, the present application allows adjusting of the dosing volume either by adjusting the hub of the actuating device acid or adjusting the position of the actuating device along a fluid conduit whose volume can be changed. Such a vara ability of the ratio of the mentioned flow resistances can be preferably achieved by designing the fluid conduit between fluid reservoir and ejection opening with a substantially linear structure, i.e. the same has a cross section without erratic cross section changes between fluid and ejection opening. In the simplest case, this can be achieved by a fluid conduit having a substantially constant cross section between fluid reservoir and ejection opening in the resting position. The present invention requires no fine-mechanical or microstructured members as required in other drop reduced and the operation security is increased. Further, the fluid carrying part can be produced as disposable members, simply of plastics, for example polyimide, whereby an expensive cleaning 'when changing media is omitted. Further, according to the invention, no limited pressure- chamber is used tor generating pressure, but a variable "active area". Thereby, optimization possibilities result for fluids by varying the displacer position, i.e. the position of the actuating device along the portion of the fluid conduit along which the cross section of the fluid conduit can be varied to effect a change of the volume of the fluid conduit. By an axially asymmetric volume change, a preferred direction of a fluid flow can be generated in the fluid conduit in the direction of the outlet opening. Further, a simple change of the maximum dosing volume can be caused by increasing the "active area", for example by using a larger displacer, wherein such change of the maximum dosing volume does not require construction changes at the fluid carrying parts. Finally, a potential pressure difference between input opening and output opening can be explicitly provided to ensure a preferred direction during refill or to avoid leaking of the liquid from the outlet opening. Thus, media that cannot be moved by capillary forces in the fluid conduit can also be dosed. Further, the present invention provide; a method for dispensing of liquids, comprising the steps of: filling a fluid conduit having a flexible tube, preferably a polymer tube, with a liquid to be dosed; effecting a volume change of a portion of the flexible tube by a displacer with adjustable hub, to thereby dispense liquid as free flying droplets or as free flying jet at an outlet opening of the fluid conduit by moving the displacer between a first end position and a second end position, wherein the tube is partly compressed at least, in the first end position or the second end position. Further, the present invention provides methods for adjusting a desired dosing volume in a dosing process by using an inventive microdosing apparatus, comprising the step of: disposing the actuating device at a predetermined position along the portion of the fluid conduit, so that due to the effecting a change of the volume of the fluid conduit, a desired dosing volume can be dispensed at the outlet opening. Further, the present invention provides a method for adjusting a desired dosing volume in a dosing process by using an inventive microdosing apparatus, comprising the step of: selecting a displacer with an axial length with regard to the portion of the fluid conduit, which is adapted to allow dispensing of a desired dosing volume in a step of effecting a change of the volume of the fluid conduit. Thus, the fire sent invention allows additional degrees of freedom when adjusting a desired dosing volume. On the one hand, with a predetermined hub and thus a predetermined displacement of the actuating device, a desired dosing volume can be adjusted by the above-described steps. If the hub and thus the displacement of the actuating device are adjustable, a desired dosing volume range can be adjusted by the above-mentioned steps, wherein then the dosing volume lying within the desired dosing volume range can be adjusted by adjusting the hub or the displacement of the actuating device, respectively. A characteristic property and a significant advantage of volume displacer systems, as they are realized by the present invention, is that in the same the dosing volume is largely independent of the viscosity of the liquid to be dosed. Above that, according to the present invention, the actuating device can be designed together with the fluid conduit to allow a full crimping of the fluid conduit by the dispiacer as an extreme case of volume displacement. In that case, additionally, a valve function can be implemented. The possibility of fully interrupting the fluid conduit between reservoir and dispensing position can thus represent a further advantage compared to known methods. In contrast to the teachings of US-3,682, 212, in the inventive microdosing apparatuses, a continuous pressure gradient is built up across the whole fluid conduit, wherein the fluid is actually pushed out of the conduit starting from the displacer. The whole fluid between displacer and outlet opening is moved in direction of the outlet opening. Acoustic phenomena play no part, since the volume displacement is performed on a time scale of a few milliseconds significantly slower than with impulse methods. Preferred embodiments of the present invention will be discussed below with reference to the accompanying drawings. They show: Figs, la schematic cross section views for explaining an - 1c embodiment of an inventive dosing process; Figs. 2a schematic views of an embodiment of an - 2d inventive microdosing apparatus; Fig. 2 schematically an image sequence of the drop formation; Fig. 4 a diagram showing drop volumes generated via a prototype; Figs. 5a schematic representations for illustration how and 5b a dosing volume range can be adjusted in an inventive microdosing apparatus; Figs. 6a schematic views for illustration how a dosing and 6b volume range can alternatively be adjusted according to the invention; Figs. 7 schematic representations of known microdosing - 9 systems; and Figs. 10a schematic representations of alternative and 10d embodiments of inventive microdosing apparatuses. With regard to the schematic representations in Figs, la to 1c, the essential features of the present invention as well as: the concept underlying the same will be discussed below. The present invention relates to an apparatus or a method, respectively, for generating microdrops or microjets, respectively, mainly in the nanoliter to picoliter range. A fluid carrying conduct is a central element of an inventive microdosing apparatus, whose inlet opening is connected to a liquid reservoir, in which the media to be dosed is located, on the other end of the conduit is an cutlet opening through which the liquid to be dosed can be dispensed. The fluid carrying conduit is preferably mainly, made of an elastic material, so that the volume of the conduit between inlet opening and outlet opening can be varied by deforming the conduit, for example compressing the same. The essential elements of an inventive dosing apparatus during different phases of a dosing process are shown in Figs, 1a t o 1c. As shown in Fig. la, a fluid conduit 100, which is an elastic polymer tube in preferred embodiments of the present invention, comprises an inlet-side end 102, which serves for connecting to a fluid reservoir, and an outlet- side end where microdrops or microjets, respectively, can be dispensed. The outlet-side end 104 can thus also be referred to as nozzle. Respective walls 106 of the elastic polymer tube 100 are illustrated in Figs. la to 1c by dotted lines. An actuator 108 in form of a displacer is provided, which has a connection part 110 where the displacer 108 can be attached to an actuating member for driving the displacer 108 . In the shown embodiment, the elastic polymer tube has a substantially constant cross section, which will normally be circular, from its input end 102 to its output end 104. In such a microdosing apparatus, an area 112 disposed below the displacer 108 can be referred to as dosing chamber area, which is defined by the position of the displacer 108 with regard to the elastic polymer tube 100. An area 114 beginning substantially at the right end of the displacer 108 represents an outlet channel fiuidicaily connecting the displacer area 112 to the outlet end 104. An area 116, which is illustrated in the figures in a reduced form and extends from the left end of the displacer 108 towards the left, represents an input channel fiuidicaily connecting the displacer area 112 to the input end 102. As further shown in Fig. la, the displacer 108 can comprise a displacer surface 120 running diagonally to the wall 106 of the polymer tube 100, which allow generation of a preferred direction of a fluid flow in direction towards the outlet opening 104 by an axially asymmetric volume change during operation of the microdosing apparatus. In the following, the mode of operation of the inventive microdosing apparatus will be discussed. When switching on the dosing system, the fluid conduit 100 will be filled automatically either by an externally generated pressure difference or by capillary forces. An externally generated pressure difference can, for example, be applied by using a fluid reservoir wherein the fluid is put under pressure . When applying a static pressure positive with regard to the outlet end coverpressure, it has to be considered that the pressure by which the liquid in the conduit 100 is provided, is not higher than the capillar forces be which the liquid is kept in the conduit, since otherwise leaking of liquid would occur from the output end 104 in the non- operated state of the microdosing apparatus. Alternatively, pressure negative with regard to the output end underpressure can be applied to avoid leaking of liquid from the output end in the non-operated state if the capillary torces are too weak. This opposing pressure has to be overcome by the capillary forces during refill. At the begining of a dosing process, in a first phase, which can be referred to as dosing phase, liquid is displaced from the conduit by reducing the conduit volume between inlet opening and outlet opening. This is achieved by moving the displacer 108 downwards, i.e. in direction towards the polymer tube 100, so that a compression of the polymer tube occurs in the displacer area 112. This downward movement is illustrated in Fig. lb by arrows 122. Thus, the displacer area 112 represents the active area of the invention microdosing apparatus . The liquid displaced from the conduit due to this volume change of the fluid conduit 100 is pressed out of the ends of the conduit or stored at another position by changing the conduit cross section when the conduit has a fluidic capacity. By the volume change of the fluid conduction 100 caused by a fast movement 122 of the displace: 108, on the one hand, a fluid flow towards the outlet, opening 104 takes place, as indicated by an arrow 124. On the other hand, a backflow into the fluid reservoir through the input channel 116 takes place, as indicated by an arrow 126. By the forward flow 124, a fluid ejection in the form of a microdrop or a microjet, respectively, takes place at the outlet opening 104 . Which portion of the fluid will be dispensed through the outlet opening 104 as jet or drop, respectively, depends on the position, type and dynamic of the volume change. As has already been mentioned above, a preferred direction of the current in the direction towards the outlet opening 104 can be affected by an axiaiiy asymmetrical volume change as caused by the displacer 103 and particularly the displacer surface 120. For generating a jet or a drop dispensed in the dosing phase at the outlet end 104, the volume change occurs sufficiently fast to transfer the required impulse to the fluid drop or fluid jet, respectively, so that the same can separate from the outlet opening 104. Thereby, both the fluid properties, such as density, viscosity, surface tension and the same, as well as a pressure difference that can exist between inlet opening and outlet opening play an important part. Further, the fiuidic resistances bet; ween outlet opening 104 and the active area 112, where in the volume change is performed i.e. the fluidic impedance of the outlet channel 114 as well as the fluidic impedance of the conduit part between active area 14 and inlet opening 112 ie. the fiuidic impedance of the inlet channel 116 i are determining for the ratio between dispensed dosing amount forward flow 124 and the fluid amount fed back into the reservoir backflow 126. A good dosing quality can, for example, be achieved when the volume change is performed close to the outlet opening 104 with high dynamic for example 50 nL within one Ey positioning the displacer close to the outlet opening be effected that the fiuidic impedance of the outlet channel 114 is low compared to the fiuidic impedance of the inlet channel 116, so that a large part of the displaced fluid is ejected from the outlet opening 104. Thereby, it can be said that the displacer is disposed close to the outlet opening 104 when the length of the inlet channel 116 is at least twice the size of the length of the outlet; channel 114, preferably at least five times as large and more preferred at least ten times as large. After the fluid drop or fluid jet, respectively, in a second phase, which can roe referred to as refill phase, the volume between inlet opening 102 and outlet opening 104 is increased again. This is achieved by moving the displacer 108 away from the fluid conduit 100 in the direction of an arrow 132, as shown in Fig. 1c. Due to this volume change, liquid flows from the reservoir through the inlet opening 102 and the inlet channel 116 into the conduit and particularly into the active area 112 of the same, as indicated in Fig. lc by arrow 134. The drawing in of air through the outlet opening 104 is prevented through capillary forces, with correspondingly small conduit cross from the reservoir can Lee determined by a hydrostatic pressure difference between inlet opening and outlet opening. For this purpose, the fluid reservoir could, for example, again be provided with pressure. At the end of the refill phase, again, the situation shown in Fig. la is present, wherein then a dosing process can be preformed again. Figs. 2a to 2d show a drop generator using an inventive microdosing apparatus with respective mounts for the fluid conduit or the actuator, respectively. Fig. 2a shows a side view of the drop generator, while 2b shows a bottom view of the same. Fig. 2c shows a sectional view along line P.-A of Fig. 2b, while Fig. ?d illustrates an enlargement of portion in the scale 5:1. The drop generator shown in Figs. 2a to 2d comprises a polyimide tube 150, which can have, for example, an inner diameter of 200 µm. For storing the polyimide tube 150, a storage block 152 and an abutment block 154 are provided. A guide groove is provided in the storage block 152 and or the abutment block 154, wherein the polyimide tube is inserted, so that the polyimide tube is securely stored between storage block and abutment block in a stabilized way. The storage block 152 and the abutment block 154 are, for example, attached to a mounting portion 160 of a mount 162 by using mounting screws 156. Further, the mount formed to hold a displacer 164 on the side of the polyimide tube 150 opposing the abutment 154, with the help of which the tube can be compressed in the active area of the same, whereby the invention volume change between inlet opening and outlet opening is obtained. Thereby, the dispiacer is driven by a piezostack actuator mot shown, whose displacement can be electronically controlled, and which is connected to the dispiacer 164 via an adapter 166. In order- to effect a preferred direction of a drop ejection 168 by the outlet opening or the polyimide tube 150, the dispiacer 164 again has a displacing surface, which is diagonal in relation to the polyimide tube, i.e. running in an angle to the same. Further, the mount 162 comprises a receiver 170 tor the driving unit. in the form of the piezostack actuator. Further, the mount 162 can have a recess 172 penetrating the same to allow attaching the same at a device, which also includes the drive unit, for example by using a screw joint. With regard to the structure shown in Figs. 2 a to 2d, a prototype has been build and successfu11y experimentailly tested. Fig. 3 shows different phases of a dosing process performed with the prototype, wherein the polyimide tube 150 is shown with its outlet end 180 in each case. Fig. 4 shows the dispensed mass in microgram with a number of 1800 dosing processes by using the prototype, wherein water has been used as liquid to be dosed. The medium drop mass was 21.57 µg, with a standard deviation a of 0.35 µg. The polyimide tube had a diameter of 200 urn. The gravimetric measurement of the reproducibility illustrated in Fig. 4 proves that a precision at least corresponding to the one of conventional dosing apparatuses and even superior to the same can be obtained with the inventive concept. With regard to Figs. 5a, 5b, 6a and 6b, it will be discussed below how a desired dosing volume or a desired dosing volume range, respectively, can be adjusted in an inventive microdosing apparatus. In Figs. 5a and 5b, the polymer tube 100 is shown schematically, whose inlet opening 102 is fluidically connected to a liquid reservoir 200 and whose outlet end 104 represents an ejection opening. The active area 112 as well as the outlet channel 114 and the inlet channel 116 are defined by the position of the displacer 108. In the arrangement shown in Fig. 5a, the input channel 116 and the outlet channel 114 have substantially the same lengths xi and so that the fluidic impedance of the same is substantially identical, when a constant cross section of the tube 100 is assumed. Thus, in the shown form of the displacer 106, which effects no preferred flow direction, a volume displacement effected by the displacer 108' would cause that flows of the same size would flow in the direction of the outlet opening 104 and the inlet opening 102. Thus, when neglecting the fluid capacity of the tube conduit 100, the volume ejected by the outlet opening 104 would be half as much as the volume displacement caused by According to Fig. 5b, the displacer 108' is disposed close to the outlet opening 104. In other words, the length of the inlet channel 116 is about five times as large as the length of the outlet channel x-. Thus, with a constant cross section of the tube 100, the fluidic impedance of the inlet channel 116 is five times as high as the one of the outlet channel 114, so that a much higher portion of the volume change effected by the displacer 103' effects a flow in the direction of the outlet opening 104 and thus an ejection through the same. In the above-mentioned way, a desired dosing volume can be adjusted by changing the position of the displacer relative to the conduit 100. Further, if the drive means of the displacer allows a selective adjusting of the hub of the same, i.e. a selective adjustment of the movement of the same by different distances vertically to the fluid conduit, so that the displacer can effect different volume changes in the dependence on its control, the above adjustment of the position can represent an adjustment of a desireo volume range, while the final adjusting of the desired dosing volume in the adjusted dosing volume range is performed by a corresponding control of the displacer. According to the invention, the dosing volume dispensed at the out Lot opening is adjustable by changing the position of the displacer, as long as the ratio of the flow resistances from inlet channel and outlet channel can be significantly changed by changing the position of the displacer. Here, significantly should mean a change which causes a change of a dosing volume dispensed at the outlet opening by at least 10, whereby the actual adjustment range with depend on across which range the position of the displace r can be adjusted. Thereby, by using the irventive microelosina apparatuses, changes of the dispensed dosing can be realized by changing the positive the displacer. This inventive adjustability of the ratio of the flow resistances of inlet channel and outlet channel is preferably enabled according to the invention in that no erratic cross section changes occur- between dosing chamber, i.e. active area, and inlet channel or outlet channel, respectively. In even more preferred embodiment;-: ot the present invention, the cross section or the fluid conduit is constant from the segment of displacement, i.e. the active area, to the outlet opening in the resting position. Further, in preferred embodiments, the whole fluid conduit between fluid reservoir and outlet opening has a substantially constant cross section. A second possibility, how a desired dosing volume or a desired dosing volume range, respectively, can be adjusted according to the invention, can be taken from E igs . 6a and 6b. According to Fig. 6a, the displacer 108' has a length along the tube 100, while according to Fig. 6b, a displacer 208 has a length along the tube 100. The length 1_ is longer than the length so that the displacer 208 allows a larger volume change of the fluid conduit 100 with the same hub. Thus, according to the indention, by changing the length of the displacer along the fluia conduit with constant hub, a desired dosing volume, or similar to the above discussions, a desired dosing volume range can be adjusted. Thus, the present invention provides a microdosing apparatus having a fluid conduit filled with a medium to be dosed, whose one end can be connected to a fluid reservoir and at whose other end an outlet opening is located, as segment of the fluid conduit can be temporally changed, so that through the volume change, fluid is dispensed as free flying droplets or as free flying jet at the outlet opening. According to the invention, the whole fluid conduit can be formed by a flexible polymer tube. Alternatively, only the mentioned determined segment can be formed by a flexible polymer tube, while feed and drain from this segment are formed by a rigid fluid conduit. As explained above, according to the invention, the displacement occurs at an elastic segment of the fluid conduit. Preferably, the elastic segment can resume the starting position in the fluid conduit, for example the flexible polymer tube or the membrane, respectively, after operation automatically, so that the displacer does not have to be connected to the fluid conduit in a fixed way, so that the fluid conduit can be designed as a simple disposable member. The present invention also comprises drop generators, wherein several inventive microdosing apparatuses are disposed in parallel. Such microdosing apparatuses disposed in parallel can be controlled separately, to dose different liquids or the same liquids. Alternatively, the drop generator can have several fluid conduits, which can be controlled simultaneously by a displacer, so that the same • or different liquids can be dosed by the same. For that purpose, the inlet ends of the different fluid conduits can be connected to the same or different liquid reservoirs. Thus, an inventive microdosing apparatus can consist of one or several microdrop generators, each having a relastic fluidic conduit filled with a medium to be dosed, whose one end has an inlet opening connected to a fluid reservoir and whose other end has an outlet opening, wherein a pressure differenc can exist between inlet opening find opening, and an actuating device by which the volume of the conduit between fluid reservoir and outlet opening can be temporally changed, wherein during a first phase the fluidic volume between inlet opening and outlet opening is reduced with sufficient speed from its initial volume to a smaller volume, whereby a microdrop or a microjet, respectively, is ejected through the outlet opening and part of the displaced volume can leak out to the inlet opening, wherein the volume of the microdrop or microjet, respectively, plus the volume receding into the reservoir through the inlet opening substantially corresponds to the volume change caused by the actuating device, and in a second phase, wherein the volume between inlet opening and outlet opening is increased again, the fluid conduit is again fi I led from the reservoir driven by pressure or capillary forces . Apart from the mount described with reference to Figs. 2a to 2d an automatic mount can be provided, which allows automatic adjustment of the position of the displacer to the fluid conduct, for example in response to a signal indicating dosing volume range or a desired dosing volume, respectively. By using the inventive microdosing apparatuses, thus, individual free flying microdroplets are generated preferabl'.' at an outlet openinq in contact with the surrounding atmosphere, to dispense fluid as free living droplets or free flying jet at the outlet opening. Thereby, the present invention allows ejecting of a droplet already with a single operating cycle of the actuating device, volume of the fluid conduit to thereby eject the droplet. The present invention allows adjusting the dosing volume by adjusting the hub of the actuating device and/or disposing the actuating device at a predetermined position along the adapted axial length can be chosen. When using an adjustable hub for adjusting the dosing volume, the hub h of the actuating de-vice or the displacer, respectively, is variable and smaller than the diameter of the tube, i.e. the cross section dimension of the same in actuating device. In the case where the whole tube cross section is crimped, i.e. the flow area is substantially brought to zero, as required in DE 4.31434 3 C2, the drop volume is determined by tube diameter. By crimping the tube, the whole volume within the relevant tube portion is displaced. Approximately, for the displaced volume which then significantly determines the drop volume with otherwise equal arrangement- the following applies: Here, 7 represents the displaced volume, a the length of the displacer and d the diameter of the tube. Compared with this, in a displacer with adjustable hub, the role. Here, the displaced volume depends on the hub h and can be approximately be described by the volume of a laterally trimmed cylinder: Here, h is the distance by which the tube is compressed. by this dependence the displaced volume on hub h and its described effect on the drop volume, the present invention allows a variable adjustment of the dosing volume without having to connect a tube with different diameter or a displacer with different dimensions, respectively. According to the invention, there is a connection between volume displacement and drop generation or drop volume, respectively, in a single dosing process, so that the present invention allows dosing with a non-periodic excitation. This is advantageous, for example, when specific non-periodic patterns are to be printed on 3 In the above-described embodiments, the actuating device is designed to effect an actuation of the tube starting from are possible where the tube is partly or fully crimped, i.e. compressed, in standby mode. A schematic cross section representation of such an embodiment is shown in Fig. 10a. The tube 100 is applied to a counter mount 300 at its backside. On the opposing side of the tube 100, a piezoactuator 301' is mounted to a mount 302 of an actuating device. A displacer 306 is disposed at the front end of the piezoactuator 302 . In the arrangement shown in Fig. 10a, the tube 100 is fully crimped in the standby mode. The dosing cycle starts with slowly pulling back the plezoactuator 302, so that the cross section of the tube 100 is partly freed. During this phase, fluid flows from the reservoir, to which the tube 100 is connected at the end 102 opposing the outlet opening 104, in the previously crimped area, in order to compensate the increasing tube volume. The actual dosing process with the drop formation at the outlet end 104 is then performed by quickly extending the piezoactuator 302 to decrease the tube volume again. As in the above-described embodiments, the dosed volume is defined by the adjustment travel of the piezoactuator 302 and can thus be controlled by varying the operating voltage or by the variation of the charging current or discharge current at the piezoactuator 302, respectively. It is an advantage of the configuration shown in Fig. l0a that the crimped tube has a significantly lower evaporation rate of dosed material compared to the normally open tube. Thus, this embodiment contains an integrated closing mechanism. However, it is a disadvantage that in commercially available conventional piezostack actuators the extended state of the piezoactuator is that state where the electric voltage is applied. When taking away the electric voltage, the piezostack actuator becomes shorter, the reduced state. Accordingly, this means that the embodiment of an integrated closing mechanism snown in Fig. 10a effects a continuous but slight energy consumption. In order to fully use the advantages of the integrated closing mechanism, it is advantageous in the embodiment shown in Fig. 10a to apply an electrical voltage continuously or to dosing system is not used. An integrated closing mechanism with reduced energy consumption can be implemented by providing the actuating device with a biasing means, for example a spring, pressing the displacer against the polymer tube in order to achieve partial or full crimping of the tube in the standby mode. Then, the actuating device preferably has an actuator, which is disposed to move the displacer against the force of the biasing means and to release the tube cross section partly or fully. An embodiment tor such an integrated closing mechanism is shown in Fict. 10b. Again, the tube 100 is applied against a counter mount 310. In this embodiment, an actuating device comprises combination of a sprinq 312 and a piezostack actuator 31-1. Further, the actuating device comprises a displacer 31c, which is rigidly coupled to an actuating plate 318. In Fig. 10b, two couplings rods 320 and 322 are shown as exemplary coupling means. The spring 312 is presses the displacer 316 against tube 100 to crimp the same in the non-operated state of the actuator 31-1. This embodiment allows the realization of a dosing apparatus whose tube is crimped with switched off electrical supply voltage, so that the same has an integrated closing mechanism without continuous energy consumption. In the off state, the displacer 316 is pressed on to the tube 100 by the spring such that the same is pressed onto the counter mount 310 and crimped. If a dosing process is to be performed, the piezoactuator 314 is extended by applying an electrical voltage, and thus the displacer 316 is reset against the sprinq force. The tube relaxes and the liquid to be dosed flows in from the reservoir connected to the side 102 of the tube opposed to the outlet opening 10-J. By quickly driving back the piezostack actuator 318, the tube 100 is again crimped via the spring 312, which is dimensioned in a sufficiently strong way. The spring is dimensioned rigidly enough so that liquid is dispensed from the outlet opening 10-1 as free flying jet. The dosed volume is again defined by the adjustment travel of the piezoactuator and can thus be controlled be varying the operating voltage or by varying the charging or discharge current in the piezostack actuator, respectively. Here, it should be noted that embodiments discussed with regard to FIGS. 10a and 10b also function when the tube is not fully. In the embed i mentis of the present invention, where the dosing volume is adjusted via the adjustable hub of the displacer or the actuating device, respectively, the displacer is moved between a first end position and the second end position, wherein the polymer tube is partly compressed in the first end position and the second end position. Thereby, the first end position defines a larger tube volume than the second end position, so that by moving the displacer from the first end position, into the second end position liquid is dosed out of the ejection end. Thereby, the first end position can define a fully relaxed state of the tube or a partly compressed state of the same. The second end position can comprise a partly compressed state or a fully compressed state of the polymer tube, in other words, in the inventive embodiments, where the dosing volume is adjustable by an adjustable hub of the actuating device, the tube wall is moved by the actuating device or by the dispiacer, respectively, 'via a part of the light cross section of the flexible polymer tube. In contrary, when fully crimping the tube from a non-crimped state to a fully crimped state, the tube wall is moved across the whole light cross section of the tube. The embodiments shown in Figs. 10a and 10b can also be implemented such that the position of the actuating device can be varied to thereby be able to vary the dosing volume dispensed from the cutlet opening. WE CLAIM: 1. A microdosing apparatus, comprising: a fluid conduit (100; 150) having a flexible tube with a first end (102) for connecting to a liquid reservoir (200) and a second end where an outlet opening (10) is located; and an actuating device having a displacer (108; 108'; 208; 306; 316) with adjustable hub, by which the volume of a portion of the flexible tube can be changed, to thereby dispense liquid as free flying droplets or as free flying jet at the outlet opening (104) by moving the displacer (108; 108'; 208; 306; 316) between a first end position and a second end position, wherein the tube is partly compressed at least in the first end position or the second end position. 2. The microdosing apparatus as claimed in claim 1, wherein the flexible tube consists of polyimide. 3. The microdosing apparatus as claimed in claim 1 or 2, wherein the flexible tube has at least one portion wherein the same has no erratic cross section changes, so that by changing the position of the actuating device (108; 108'; 164; 208) along the portion, a ratio of a fluidic impedance between the position of the actuating device and the outlet opening (104) to a fluidic impedance between the first end (102) and the position of the actuating device is variable, so that the liquid volume output at the outlet opening (104) is variable by at least 10%. 4. The microdosing apparatus as claimed in one of claim 1 to 3, wherein the tube can be compressed across a predetermined length by the displacer (108; 108'; 208; 306; 316) in order to effect the volume change of the tube. 5. The microdosing apparatus as claimed in claim 4, wherein the displacer (108) has a form to effect an axially asymmetric volume change with regard to the tube. 6. The microdosing apparatus as claimed in one of claims 1 to 5, comprising means (150, 152, 162) for holding the actuating device at one or the position along the tube. 7. The microdosing apparatus as claimed in one of claims 1 to 6, comprising a biasing means (312), to bias the tube into a fully or partly compressed state through a displacer (316). 8. The microdosing apparatus as claimed in claim 7, wherein the actuating device has an actuator (314, 320, 322), which is disposed to move the displacer (316) against the bias of the biasing means (312). 9. A microdosing apparatus, comprising: a fluid conduit (100; 150) with a first end (102) for connecting to a fluid reservoir (100) and a second end where an outlet opening (104) is located, the fluid conduit (100; 150) having a portion along which a cross section of the fluid conduit can be varied to effect a change of the volume of the fluid conduit; an actuating device (108'; 164; 208) disposed at a position along the portion of the fluid conduit for effecting a change of the volume of the fluid conduit to thereby dispense liquid as free flying droplets or free flying jet from the outlet opening (104), wherein a ratio of a fluidic impedance between the position of the actuating device (108; 108;; 164; 208) and the outlet opening (104) to a fluidic impedance between the first end (102) and the fluid conduit (100; 150) and the position of the actuating device is variable by changing the position of the actuating device, so that a volume dispensed at the outlet opening (104) is thereby variable by at least 10%. 10. The microdosing apparatus as claimed in claim 9, wherein the actuating device has a displacer (108; 108'; 164; 208) by which the portion of the fluid conduit (100; 150) can be compressed across a predetermined length to effect the volume change of the portion of the fluid conduit. 11. The microdosing apparatus as claimed in claim 10, wherein the displacer (108) has a form to effect an axially asymmetric volume change with regard to the portion of the fluid conduit (100; 150). 12. The microdosing apparatus as claimed in one of claims 9 to 11, comprising means (150, 152, 162) for holding the actuating device at the position along the portion of the fluid conduit. 13. The microdosing apparatus as claimed in one of claims 1 to 12, wherein the fluid conduit (100; 150) has no erratic cross section changes between the first end (102) and the outlet opening (104) in the resting state. 14. The microdosing apparatus as claimed in one claims 1 to 12, wherein the fluid conduit (100; 150) has a substantially constant cross section between the first end (102) and the outlet opening (104) in the resting position. 15. The microdosing apparatus as claimed in one of claims 1 to 14, comprising means for providing the fluid conduit with a pressure difference. 16. The microdosing apparatus as claimed in one of claims 1 to 15, wherein the fluid conduit (100; 150) has such a cross section area that a liquid to be dosed can be moved through the same by capillary forces. 17. The microdosing apparatus as claimed in one of claims 1 to 16, comprising a plurality of respective fluid conduits, so that several equal or different liquids can be dispensed simultaneously or successively. 18. The microdosing apparatus as claimed in claim 17, comprising an actuating device for simultaneously effecting the volume change of the plurality of fluid conduits. 19. The microdosing apparatus as claimed in claim 18, wherein the actuating device is a common displacer. 20. A method for dispensing a desired volume of liquids in a microdosing apparatus, the method comprising the steps of: filling a fluid conduit (100; 150) having a flexible tube with a liquid to be dispensed; effecting a volume change of a portion of the flexible tube by a displacer (108; 108'; 208; 306; 316) with adjustable hub, to thereby dispense liquid as free flying droplets or as free flying jet at an outlet opening (104) of the fluid conduit (100; 150) by moving the displacer (108; 108'; 208; 306; 316) between a first end position and a second end position, wherein the tube is partly compressed at least in the first end position or the second end position. 21. The method as claimed in claim 20, comprising the step of providing a displacer (108; 108'; 164; 208) at a position along the tube, by which the tube can be compressed across a predetermined length to effect the volume change of the portion of the same. 22. The method as claimed in claim 21, wherein the fluid conduit (100; 150) has a first end (102) connected to a fluid reservoir (200) and a second end where the outlet opening (104) is located, comprising the step of: selecting the position of the displacer along the tube to adjust a ratio of a fluidic impedance between the position of the displacer (108; 108'; 164; 208) and the outlet opening (104) to a fluidic impedance between the first end (102) and the position of the actuating device, to thereby dispense a desired liquid volume at the outlet opening (104) by effecting the volume change. 23. The method as claimed in claim 21 or 22, comprising a step of selecting a displacer (108; 108'; 164; 208) with a length axial with regard to the flexible tube, to effect the volume change by using the displacer and to dispense a desired liquid volume at the outlet opening (104). 24. The method as claimed in one of claims 22 to 23, wherein in the step of effecting the volume change, a volume change axially asymmetric with regard to the flexible tube is performed to effect a fluid flow with a preferred direction towards the outlet opening (104) in the fluid conduit (100; 150). 25. The method as claimed in one of claims 20 to 24, comprising a step of providing the fluid conduit (100; 150) with a static pressure. 26. The method as claimed in claim 25, wherein the static pressure with regard to the outlet end is an overpressure to effect a fluid flow with a preferred direction towards the outlet opening (104) when effecting the volume change in the fluid conduit (100; 150), and/or to support a refill after a dispensing process. 27. The method as claimed in claim 25, wherein the static pressure with regard to the outlet end is a subpressure to prevent leaking of liquid from the outlet end when no volume change is effected. 28. The method as claimed in one of claims 20 to 27, comprising a step of reversing the volume change after the step of effecting a volume change, so that the tube returns to the initial state, wherein during this step a capillary refill of the fluid conduit (100; 150) takes place. 29. A method for dispensing a desired volume of a liquid in a dispensing process adapting a microdosing apparatus as claimed in claim 10, the method comprising the step of: disposing the actuating device (108; 108'; 164) at a predetermined position along the portion of the fluid conduit (100; 150), so that due to the resulting ratio of fluidic impedances in the step of effecting a change of the volume of the liquid conduit (10; 150), a desired liquid volume can be dispensed at the outlet opening (104). 30. A method for dispensing a desired volume of a liquid in a dispensing process adapting a microdosing apparatus, the method comprising the step of: selecting a displacer (108; 108'; 164; 208) with an axial length (11, 12) with regard to the portion of the fluid conduit (100; 150), which is adapted to allow dispensing of a desired volume at the outlet opening (104) in the step of effecting a change of the volume of the liquid conduit (100; 150). The invention relates to a microdosing apparatus, comprising a fluid conduit (100; 150) having a flexible tube with a first end (102) for connecting to a liquid reservoir (200) and a second end where an outlet opening (10) is located; and an actuating device having a displacer (108; 108'; 208; 306; 316) with adjustable hub, by which the volume of a portion of the flexible tube can be changed, to thereby dispense liquid as free flying droplets or as free flying jet at the outlet opening (104) by moving the displacer (108; 108'208; 306; 316) between a first end position and a second end position, wherein the tube is partly compressed at least in the first end position or the second end position.

Full Text

Description
The present invention relates to a microdosing apparatus,
to methods for dosed dispensing of liquids and to methods
tor adjusting a desired dosing volume range when using an
incentive microdos ing apparatus.
According to the prior art, volumes in the nanoliter range
require specific methods to ensure the required precision.
Here, in addition to contact methods, conventional
dispensing methods, pin printing methods, etc., contactless
methods are of significant importance.
A class of known methods is based on fast-switching valves.
Therefore, a suitable valve, mostly based on magnetic or
piezoelectrical drives, is connected to a media reservoir
via a conduit and pressure is built up in the same. By the
than 1 ms, a very large flow is generated for a short term,
so that the fluid, even with high surface tensions, can
separate from the dispensing position and can impinge on
the substrate as free jet. The closing amount can be
controlled by the pressure and/or the switchinq time of the
valve.
Different approaches exist for generating the pressure,
there are in the above-described concept with switched
valves.
A schematic representation showing a first known approach,
which can be referred to as syringe solenoid method, is

shown in Fig. 7. Here, a fluid conduit 10 is fluidically
connected to a syringe 14, which can be removable, via a
fast-switching microsolenoid valve 12. At the lower end of
the syringe 14, there is a nozzle opening 16. The opposite
end of the fluid conduit 10 is connected to a syringe pump
20 via a switching valve 18. Further, a fluid reservoir 22
is also connected to the switching valve 18 via a further
f1uid conduit 24.
The switching valve 18 has two switching states. In a first
switching state, a pump chamber 26 of the syringe pump 20
is fluidically connected to the fluid reservoir 22 via the
fluid conduit 24, so that liquid 28 can be drawn from the
fluid reservoir into the pump chamber 26, by increasing the
volume of the pump chamber 26 by a corresponding movement
of the piston 30 of the syringe pump. This process serves
process, the switching valve 13 is switched to effect a
fluidic connection of the pump chamber 2 6 to the
microsolenoid valve 12 via the fluid conduit 10. By using
the piston 30, pressure is applied to the liquid inside the
pump chamber 26, so that by fast switching the
microsolenoid valve 12 switching time 1 mi, liquid can
Dosing apparatuses of the type shown in Fig. 7 are, for
example, sold by the company Cartesian.
An alternative principle, as is practiced, for example, by
the companies Delo and Vermes, is shown in Fig. 8. In this
alternative method, a pressure container 40 is provided,
containing liquid 42 under pressure. An outlet of the
pressure container 40 is connected to a quickly switchable
valve 46 via a fluid conduit 44, which is again connected
to a nozzle opening, shown merely schematically as arrow in
Fig. 8, via a fluid conduit 48. In this arrangement, liquid
can also be dispensed in a free jet from the nozzle opening
by fast switching of the valve 46.

described in DE.-A- 1 9-02 36" , DF-A-19802368 and EP-A-0725267.
The microdOSinq apparatuses described there comprise a pump
chamber abutting to a flexible membrane and connected to a
reservoir "ia a supply line and to a nozzle opening via a
drain. An example for such a microdosing apparatus will be
discussed below with reference to Figs. 9a - 9c.
microdosing apparatus in the resting position is shown. The
dosing apparatus comprises a dosing head 50 and an
actuating 'device 52. In the shown example, the dosing head
50 is formed by two interconnected substrates 54, 56, in
which respective recesses are formed. The first substrate
5-1 is structured such that a reservoir connection 58, an
inlet channel 60 and a dosing chamber 62 are formed in the
same. The lower substrate 56 is structured such that a
nozzle connection 6-1, a nozzle 66 having a nozzle channel
and an outlet opening, and an outlet area 68 having a
significantly larger cross section than the outlet opening
Further, a membrane 64 is formed the upper substrate 54 by
the structuring of the same.
The actuating device 52 has a displacer 72, by which the
membrane can be deflected downwards to reduce the volume
of the dosing chamber 62, as shown in Fig. 9b. By this
reduction oi the volume or the dosing chamber z, on the
one hand, a backflow 74 results through the inlet channel
60 and the reservoir connection 58. On the other hand, a
forward flow results through the nozzle connection 64 and
the nozzle 66, so that dispensing liquid 76 takes place at
the outlet end of the nozzle 66. The ratio between backflow
74 and dosed liquid 76 depends on the ratio of flow
resistance of fluid connection between reservoir and dosing
chamber to the flow resistance between dosing chamber and
outlet opening of the nozzle 66.

Alter the dosing process, the displacer 72 is moved upwards
by using the actuating device 52, see Fig. 9c, so that the
same finally resumes its original position by elasticity,
as shown in Fig. 9a. By this resetting of the membrane 70,
an increase of the volume of the dosing chamber 62 results,
so that a refill flow 78 from the reservoir through the
reservoir connection 58 and the inlet channel 60 occurs. In
order to avoid an intake of air through the nozzle 66
during this phase, resetting the membrane 70 has to be
performed slowly enough, so that capillary forces keeping
the liquid in nozzle 66 are not overcome thereby.
Microdosing apparatuses as described above with reference
to Figs. 9a - 9c have originally been developed for enzyme
dosage in biochemistry. By using these apparatuses, liquids
with viscosities up to 100 mPas in a volume range of 1 nL
to 1000 nL can be dosed very media independent and
precisely. The liquid to be dosed is thereby dosed by
displacing a dosing chip, preferably made of silicon, in
free jet from the dosing chamber, which is. However, this
method requires a comparatively complex micro device.
Finally, a droplet ejection system is known from U.S
3,683,212, wherein a tube shaped piezoconverter connects a
fluid conduit to a nozzle plate wherein a nozzle opening is
formed. A voltage pulse with short rise time is applied to
the converter to effect contraction of the converter. The
resulting sudden decrease of the enclosed volume causes a
small amount of fluid to be ejected from the opening in the
opening plate. Thereby, the liquid is kept under no or no
low pressure. The surface tension at the opening prevents
that liquid flows out when the converter is not operated.
The ejected liquid is replaced by a capillary forward flow
of liquid in the conduit.
It has been found out that according to US- 3 , 683,212, the
drop is generated with the help of an acoustic principle

similar to the piezoelectric inkjet methods. Here, an
acoustic pressure wave is generated in a rigid fluid
conduit, for example a rigid glass capillary, which results
in a high pressure gradient locally at an output position,
which leads to drop separation. The actuating time of the
actuator iS here in the range of the sound propagation in
the system, which is normally several microseconds. Thus,
in this context, the acoustic impedance of the fluid
conduits below and above the actuator is of significance
for the design. Thus, this is an impulse method where a
high acoustic impulse is generated with a low volume
displacement. In other words, a sound wave with pressure
maxima and pressure minima is generated between the
actuation position and the disposing position, wherein
ejection of liquid is effected at the dispensing position
by a corresponding pressure. According to US 3,683,212, the
fluid conduct is only negligibly deformed, the actuator
mainly only transmits sound and the elasticity of the fluid
conduit has no significant importance.
From DE 4 313 C2, an apparatus for dosing liquids is
known, having a liquid supply tube connected if one end
a liquid reservoir and open at the other end. The tube is
applied to an abutment socket and a hammer is provided on
the side opposing the abutment socket of the tube. The
hammer can vibrated periodically in a direction transversal
to the tube axis, so that the whole tube cross section is
crimped by the hammer, i.e. the flow area is substantially
brought to zero. Therebv, impulsive force impact's are
exerted on the tube and individual liquid drops are driven
out of the open end.
Tt is the ohiect of the present invention to provide a
microdosing apparatus with a simple structure, which
further preferably allows an easy change of a dosing volume
to be dispensed. It is a further object of the present
invention to provide a method for dosed dispensing of
liquids.

This object is achieved by microdosing apparatuses
according to claims 1 and 9 and a method according to claim
20, 29 and 30 .
The present nvention provides a microdosing apparatus
comprising:
a fluid conduit having a flexible tube, preferably a
polymer tube, with a first end for connecting to a liquid
reservoir and a second end where an output opening is
located; and
an actuating device having a displacer with adjustable hub,
by which the volume of a portion of the flexible tube can
be changed, to thereby dispense liquid as free flying
droplets or as free flying jet at the outlet opening by
moving the displacer between the first end position and the
second end position, wherein the tube is partly compressed
at least in the first end position or the second end
position.
Further, the present invention provides a microdosing
apparatus, comprising:
reservoir and a second end where an outlet opening is
located, the fluid conduit having a portion along which a
cross section of the fluid conduit can be varied to effect
a change of the volume of the fluid conduit;
portion of the fluid conduit for effecting a change of the
volume oi the fluid conduit to thereby dispense liquid as
free flyiny droplets or free flying jet from the outlet
opening;

wherein a ratio of the fluidic impedance between the
position of the actuating device and the outlet opening to
a fluidic impedance between the fluid reservoir and the
position of the actuating device is variable by changing
the position of the actuating device, so that a dosing
volume dispensed at the outlet opening is variable by at
least 10
Here, impedance means the combination oi fluidic
resistance and fluidic inductance determined by the length
and the flow cross section of a line.
Thus, the present application allows adjusting of the
dosing volume either by adjusting the hub of the actuating
device acid or adjusting the position of the actuating
device along a fluid conduit whose volume can be changed.
Such a vara ability of the ratio of the mentioned flow
resistances can be preferably achieved by designing the
fluid conduit between fluid reservoir and ejection opening
with a substantially linear structure, i.e. the same has a
cross section without erratic cross section changes between
fluid and ejection opening. In the simplest case,
this can be achieved by a fluid conduit having a
substantially constant cross section between fluid
reservoir and ejection opening in the resting position.
The present invention requires no fine-mechanical or
microstructured members as required in other drop
reduced and the operation security is increased. Further,
the fluid carrying part can be produced as disposable
members, simply of plastics, for example polyimide, whereby
an expensive cleaning 'when changing media is omitted.
Further, according to the invention, no limited pressure-
chamber is used tor generating pressure, but a variable
"active area". Thereby, optimization possibilities result

for fluids by varying the displacer position,
i.e. the position of the actuating device along the portion
of the fluid conduit along which the cross section of the
fluid conduit can be varied to effect a change of the
volume of the fluid conduit. By an axially asymmetric
volume change, a preferred direction of a fluid flow can be
generated in the fluid conduit in the direction of the
outlet opening. Further, a simple change of the maximum
dosing volume can be caused by increasing the "active
area", for example by using a larger displacer, wherein
such change of the maximum dosing volume does not require
construction changes at the fluid carrying parts. Finally,
a potential pressure difference between input opening and
output opening can be explicitly provided to ensure a
preferred direction during refill or to avoid leaking of
the liquid from the outlet opening. Thus, media that cannot
be moved by capillary forces in the fluid conduit can also
be dosed.
Further, the present invention provide; a method for
dispensing of liquids, comprising the steps of:
filling a fluid conduit having a flexible tube, preferably
a polymer tube, with a liquid to be dosed;
effecting a volume change of a portion of the flexible tube
by a displacer with adjustable hub, to thereby dispense
liquid as free flying droplets or as free flying jet at an
outlet opening of the fluid conduit by moving the displacer
between a first end position and a second end position,
wherein the tube is partly compressed at least, in the first
end position or the second end position.
Further, the present invention provides methods for
adjusting a desired dosing volume in a dosing process by
using an inventive microdosing apparatus, comprising the
step of:

disposing the actuating device at a predetermined position
along the portion of the fluid conduit, so that due to the
effecting a change of the volume of the fluid conduit, a
desired dosing volume can be dispensed at the outlet
opening.
Further, the present invention provides a method for
adjusting a desired dosing volume in a dosing process by
using an inventive microdosing apparatus, comprising the
step of:
selecting a displacer with an axial length with regard to
the portion of the fluid conduit, which is adapted to allow
dispensing of a desired dosing volume in a step of
effecting a change of the volume of the fluid conduit.
Thus, the fire sent invention allows additional degrees of
freedom when adjusting a desired dosing volume. On the one
hand, with a predetermined hub and thus a predetermined
displacement of the actuating device, a desired dosing
volume can be adjusted by the above-described steps. If the
hub and thus the displacement of the actuating device are
adjustable, a desired dosing volume range can be adjusted
by the above-mentioned steps, wherein then the dosing
volume lying within the desired dosing volume range can be
adjusted by adjusting the hub or the displacement of the
actuating device, respectively.
A characteristic property and a significant advantage of
volume displacer systems, as they are realized by the
present invention, is that in the same the dosing volume is
largely independent of the viscosity of the liquid to be
dosed.
Above that, according to the present invention, the
actuating device can be designed together with the fluid
conduit to allow a full crimping of the fluid conduit by

the dispiacer as an extreme case of volume displacement. In
that case, additionally, a valve function can be
implemented. The possibility of fully interrupting the
fluid conduit between reservoir and dispensing position can
thus represent a further advantage compared to known
methods.
In contrast to the teachings of US-3,682, 212, in the
inventive microdosing apparatuses, a continuous pressure
gradient is built up across the whole fluid conduit,
wherein the fluid is actually pushed out of the conduit
starting from the displacer. The whole fluid between
displacer and outlet opening is moved in direction of the
outlet opening. Acoustic phenomena play no part, since the
volume displacement is performed on a time scale of a few
milliseconds significantly slower than with impulse
methods.
Preferred embodiments of the present invention will be
discussed below with reference to the accompanying
drawings. They show:
Figs, la schematic cross section views for explaining an
- 1c embodiment of an inventive dosing process;
Figs. 2a schematic views of an embodiment of an
- 2d inventive microdosing apparatus;
Fig. 2 schematically an image sequence of the drop
formation;
Fig. 4 a diagram showing drop volumes generated via a
prototype;
Figs. 5a schematic representations for illustration how
and 5b a dosing volume range can be adjusted in an
inventive microdosing apparatus;

Figs. 6a schematic views for illustration how a dosing
and 6b volume range can alternatively be adjusted
according to the invention;
Figs. 7 schematic representations of known microdosing
- 9 systems; and
Figs. 10a schematic representations of alternative
and 10d embodiments of inventive microdosing
apparatuses.
With regard to the schematic representations in Figs, la to
1c, the essential features of the present invention as well
as: the concept underlying the same will be discussed below.
The present invention relates to an apparatus or a method,
respectively, for generating microdrops or microjets,
respectively, mainly in the nanoliter to picoliter range. A
fluid carrying conduct is a central element of an inventive
microdosing apparatus, whose inlet opening is connected to
a liquid reservoir, in which the media to be dosed is
located, on the other end of the conduit is an cutlet
opening through which the liquid to be dosed can be
dispensed. The fluid carrying conduit is preferably mainly,
made of an elastic material, so that the volume of the
conduit between inlet opening and outlet opening can be
varied by deforming the conduit, for example compressing
the same.
The essential elements of an inventive dosing apparatus
during different phases of a dosing process are shown in
Figs, 1a t o 1c.
As shown in Fig. la, a fluid conduit 100, which is an
elastic polymer tube in preferred embodiments of the
present invention, comprises an inlet-side end 102, which
serves for connecting to a fluid reservoir, and an outlet-
side end where microdrops or microjets, respectively,

can be dispensed. The outlet-side end 104 can thus also be
referred to as nozzle. Respective walls 106 of the elastic
polymer tube 100 are illustrated in Figs. la to 1c by
dotted lines.
An actuator 108 in form of a displacer is provided, which
has a connection part 110 where the displacer 108 can be
attached to an actuating member for driving the displacer
108 .
In the shown embodiment, the elastic polymer tube has a
substantially constant cross section, which will normally
be circular, from its input end 102 to its output end 104.
In such a microdosing apparatus, an area 112 disposed below
the displacer 108 can be referred to as dosing chamber
area, which is defined by the position of the displacer 108
with regard to the elastic polymer tube 100. An area 114
beginning substantially at the right end of the displacer
108 represents an outlet channel fiuidicaily connecting the
displacer area 112 to the outlet end 104. An area 116,
which is illustrated in the figures in a reduced form and
extends from the left end of the displacer 108 towards the
left, represents an input channel fiuidicaily connecting
the displacer area 112 to the input end 102.
As further shown in Fig. la, the displacer 108 can comprise
a displacer surface 120 running diagonally to the wall 106
of the polymer tube 100, which allow generation of a
preferred direction of a fluid flow in direction towards
the outlet opening 104 by an axially asymmetric volume
change during operation of the microdosing apparatus.
In the following, the mode of operation of the inventive
microdosing apparatus will be discussed.

When switching on the dosing system, the fluid conduit 100
will be filled automatically either by an externally
generated pressure difference or by capillary forces.
An externally generated pressure difference can, for
example, be applied by using a fluid reservoir wherein the
fluid is put under pressure .
When applying a static pressure positive with regard to the
outlet end coverpressure, it has to be considered that the
pressure by which the liquid in the conduit 100 is
provided, is not higher than the capillar forces be which
the liquid is kept in the conduit, since otherwise leaking
of liquid would occur from the output end 104 in the non-
operated state of the microdosing apparatus.
Alternatively, pressure negative with regard to the output
end underpressure can be applied to avoid leaking of
liquid from the output end in the non-operated state if the
capillary torces are too weak. This opposing pressure has
to be overcome by the capillary forces during refill.
At the begining of a dosing process, in a first phase,
which can be referred to as dosing phase, liquid is
displaced from the conduit by reducing the conduit volume
between inlet opening and outlet opening. This is achieved
by moving the displacer 108 downwards, i.e. in direction
towards the polymer tube 100, so that a compression of the
polymer tube occurs in the displacer area 112. This
downward movement is illustrated in Fig. lb by arrows 122.
Thus, the displacer area 112 represents the active area of
the invention microdosing apparatus .
The liquid displaced from the conduit due to this volume
change of the fluid conduit 100 is pressed out of the ends
of the conduit or stored at another position by changing
the conduit cross section when the conduit has a fluidic
capacity.

By the volume change of the fluid conduction 100 caused by
a fast movement 122 of the displace: 108, on the one hand,
a fluid flow towards the outlet, opening 104 takes place, as
indicated by an arrow 124. On the other hand, a backflow
into the fluid reservoir through the input channel 116
takes place, as indicated by an arrow 126. By the forward
flow 124, a fluid ejection in the form of a microdrop or a
microjet, respectively, takes place at the outlet opening
104 .
Which portion of the fluid will be dispensed through the
outlet opening 104 as jet or drop, respectively, depends on
the position, type and dynamic of the volume change. As has
already been mentioned above, a preferred direction of the
current in the direction towards the outlet opening 104 can
be affected by an axiaiiy asymmetrical volume change as
caused by the displacer 103 and particularly the displacer
surface 120. For generating a jet or a drop dispensed in
the dosing phase at the outlet end 104, the volume change
occurs sufficiently fast to transfer the required impulse
to the fluid drop or fluid jet, respectively, so that the
same can separate from the outlet opening 104. Thereby,
both the fluid properties, such as density, viscosity,
surface tension and the same, as well as a pressure
difference that can exist between inlet opening and outlet
opening play an important part. Further, the fiuidic
resistances bet; ween outlet opening 104 and the active area
112, where in the volume change is performed i.e. the
fluidic impedance of the outlet channel 114 as well as the
fluidic impedance of the conduit part between active area
14 and inlet opening 112 ie. the fiuidic impedance of the
inlet channel 116 i are determining for the ratio between
dispensed dosing amount forward flow 124 and the fluid
amount fed back into the reservoir backflow 126. A good
dosing quality can, for example, be achieved when the
volume change is performed close to the outlet opening

104 with high dynamic for example 50 nL within one
Ey positioning the displacer close to the outlet opening
be effected that the fiuidic impedance of the
outlet channel 114 is low compared to the fiuidic impedance
of the inlet channel 116, so that a large part of the
displaced fluid is ejected from the outlet opening 104.
Thereby, it can be said that the displacer is disposed
close to the outlet opening 104 when the length of the
inlet channel 116 is at least twice the size of the length
of the outlet; channel 114, preferably at least five times
as large and more preferred at least ten times as large.
After the fluid drop or fluid jet, respectively,
in a second phase, which can roe referred to as refill
phase, the volume between inlet opening 102 and outlet
opening 104 is increased again. This is achieved by moving
the displacer 108 away from the fluid conduit 100 in the
direction of an arrow 132, as shown in Fig. 1c. Due to this
volume change, liquid flows from the reservoir through the
inlet opening 102 and the inlet channel 116 into the
conduit and particularly into the active area 112 of the
same, as indicated in Fig. lc by arrow 134. The drawing in
of air through the outlet opening 104 is prevented through
capillary forces, with correspondingly small conduit cross
from the reservoir can Lee determined by a hydrostatic
pressure difference between inlet opening and outlet
opening. For this purpose, the fluid reservoir could, for
example, again be provided with pressure.
At the end of the refill phase, again, the situation shown
in Fig. la is present, wherein then a dosing process can be
preformed again.
Figs. 2a to 2d show a drop generator using an inventive
microdosing apparatus with respective mounts for the fluid

conduit or the actuator, respectively. Fig. 2a shows a side
view of the drop generator, while 2b shows a bottom view of
the same. Fig. 2c shows a sectional view along line P.-A of
Fig. 2b, while Fig. ?d illustrates an enlargement of
portion in the scale 5:1.
The drop generator shown in Figs. 2a to 2d comprises a
polyimide tube 150, which can have, for example, an inner
diameter of 200 µm. For storing the polyimide tube 150, a
storage block 152 and an abutment block 154 are provided. A
guide groove is provided in the storage block 152 and or
the abutment block 154, wherein the polyimide tube is
inserted, so that the polyimide tube is securely stored
between storage block and abutment block in a stabilized
way. The storage block 152 and the abutment block 154 are,
for example, attached to a mounting portion 160 of a mount
162 by using mounting screws 156. Further, the mount formed to hold a displacer 164 on the side of the polyimide
tube 150 opposing the abutment 154, with the help of which
the tube can be compressed in the active area of the same,
whereby the invention volume change between inlet opening
and outlet opening is obtained. Thereby, the dispiacer is
driven by a piezostack actuator mot shown, whose
displacement can be electronically controlled, and which is
connected to the dispiacer 164 via an adapter 166. In order-
to effect a preferred direction of a drop ejection 168 by
the outlet opening or the polyimide tube 150, the dispiacer
164 again has a displacing surface, which is diagonal in
relation to the polyimide tube, i.e. running in an angle to
the same.
Further, the mount 162 comprises a receiver 170 tor the
driving unit. in the form of the piezostack actuator.
Further, the mount 162 can have a recess 172 penetrating
the same to allow attaching the same at a device, which
also includes the drive unit, for example by using a screw
joint.

With regard to the structure shown in Figs. 2 a to 2d, a
prototype has been build and successfu11y experimentailly
tested. Fig. 3 shows different phases of a dosing process
performed with the prototype, wherein the polyimide tube
150 is shown with its outlet end 180 in each case.
Fig. 4 shows the dispensed mass in microgram with a number
of 1800 dosing processes by using the prototype, wherein
water has been used as liquid to be dosed. The medium drop
mass was 21.57 µg, with a standard deviation a of 0.35 µg.
The polyimide tube had a diameter of 200 urn. The
gravimetric measurement of the reproducibility illustrated
in Fig. 4 proves that a precision at least corresponding to
the one of conventional dosing apparatuses and even
superior to the same can be obtained with the inventive
concept.
With regard to Figs. 5a, 5b, 6a and 6b, it will be
discussed below how a desired dosing volume or a desired
dosing volume range, respectively, can be adjusted in an
inventive microdosing apparatus.
In Figs. 5a and 5b, the polymer tube 100 is shown
schematically, whose inlet opening 102 is fluidically
connected to a liquid reservoir 200 and whose outlet end
104 represents an ejection opening. The active area 112 as
well as the outlet channel 114 and the inlet channel 116
are defined by the position of the displacer 108. In the
arrangement shown in Fig. 5a, the input channel 116 and the
outlet channel 114 have substantially the same lengths xi
and so that the fluidic impedance of the same is
substantially identical, when a constant cross section of
the tube 100 is assumed. Thus, in the shown form of the
displacer 106, which effects no preferred flow direction,
a volume displacement effected by the displacer 108' would
cause that flows of the same size would flow in the
direction of the outlet opening 104 and the inlet opening
102. Thus, when neglecting the fluid capacity of the tube

conduit 100, the volume ejected by the outlet opening 104
would be half as much as the volume displacement caused by
According to Fig. 5b, the displacer 108' is disposed close
to the outlet opening 104. In other words, the length of
the inlet channel 116 is about five times as large as the
length of the outlet channel x-. Thus, with a constant
cross section of the tube 100, the fluidic impedance of the
inlet channel 116 is five times as high as the one of the
outlet channel 114, so that a much higher portion of the
volume change effected by the displacer 103' effects a flow
in the direction of the outlet opening 104 and thus an
ejection through the same.
In the above-mentioned way, a desired dosing volume can be
adjusted by changing the position of the displacer relative
to the conduit 100. Further, if the drive means of
the displacer allows a selective adjusting of the hub of
the same, i.e. a selective adjustment of the movement of
the same by different distances vertically to the fluid
conduit, so that the displacer can effect different volume
changes in the dependence on its control, the above
adjustment of the position can represent an adjustment of a
desireo volume range, while the final adjusting of
the desired dosing volume in the adjusted dosing volume
range is performed by a corresponding control of the
displacer.
According to the invention, the dosing volume dispensed at
the out Lot opening is adjustable by changing the position
of the displacer, as long as the ratio of the flow
resistances from inlet channel and outlet channel can be
significantly changed by changing the position of the
displacer. Here, significantly should mean a change which
causes a change of a dosing volume dispensed at the outlet
opening by at least 10, whereby the actual adjustment
range with depend on across which range the position of the

displace r can be adjusted. Thereby, by using the irventive
microelosina apparatuses, changes of the dispensed dosing
can be realized by changing the
positive the displacer. This inventive adjustability of
the ratio of the flow resistances of inlet channel and
outlet channel is preferably enabled according to the
invention in that no erratic cross section changes occur-
between dosing chamber, i.e. active area, and inlet channel
or outlet channel, respectively. In even more preferred
embodiment;-: ot the present invention, the cross section or
the fluid conduit is constant from the segment of
displacement, i.e. the active area, to the outlet opening
in the resting position. Further, in preferred embodiments,
the whole fluid conduit between fluid reservoir and outlet
opening has a substantially constant cross section.
A second possibility, how a desired dosing volume or a
desired dosing volume range, respectively, can be adjusted
according to the invention, can be taken from E igs . 6a and
6b. According to Fig. 6a, the displacer 108' has a length
along the tube 100, while according to Fig. 6b, a
displacer 208 has a length along the tube 100. The
length 1_ is longer than the length so that the
displacer 208 allows a larger volume change of the fluid
conduit 100 with the same hub. Thus, according to the
indention, by changing the length of the displacer along
the fluia conduit with constant hub, a desired dosing
volume, or similar to the above discussions, a desired
dosing volume range can be adjusted.
Thus, the present invention provides a microdosing
apparatus having a fluid conduit filled with a medium to be
dosed, whose one end can be connected to a fluid reservoir
and at whose other end an outlet opening is located, as
segment of the fluid conduit can be temporally changed, so
that through the volume change, fluid is dispensed as free
flying droplets or as free flying jet at the outlet

opening. According to the invention, the whole fluid
conduit can be formed by a flexible polymer tube.
Alternatively, only the mentioned determined segment can be
formed by a flexible polymer tube, while feed and drain
from this segment are formed by a rigid fluid conduit.
As explained above, according to the invention, the
displacement occurs at an elastic segment of the fluid
conduit. Preferably, the elastic segment can resume the
starting position in the fluid conduit, for example the
flexible polymer tube or the membrane, respectively, after
operation automatically, so that the displacer does not
have to be connected to the fluid conduit in a fixed way,
so that the fluid conduit can be designed as a simple
disposable member.
The present invention also comprises drop generators,
wherein several inventive microdosing apparatuses are
disposed in parallel. Such microdosing apparatuses disposed
in parallel can be controlled separately, to dose different
liquids or the same liquids. Alternatively, the drop
generator can have several fluid conduits, which can be
controlled simultaneously by a displacer, so that the same •
or different liquids can be dosed by the same. For that
purpose, the inlet ends of the different fluid conduits can
be connected to the same or different liquid reservoirs.

Thus, an inventive microdosing apparatus can consist of one
or several microdrop generators, each having a relastic
fluidic conduit filled with a medium to be dosed, whose one
end has an inlet opening connected to a fluid reservoir and
whose other end has an outlet opening, wherein a pressure
differenc can exist between inlet opening find
opening, and an actuating device by which the volume of the
conduit between fluid reservoir and outlet opening can be
temporally changed, wherein during a first phase the
fluidic volume between inlet opening and outlet opening is
reduced with sufficient speed from its initial volume to a
smaller volume, whereby a microdrop or a microjet,
respectively, is ejected through the outlet opening and
part of the displaced volume can leak out to the inlet
opening, wherein the volume of the microdrop or microjet,
respectively, plus the volume receding into the reservoir
through the inlet opening substantially corresponds to the
volume change caused by the actuating device, and in a
second phase, wherein the volume between inlet opening and
outlet opening is increased again, the fluid conduit is
again fi I led from the reservoir driven by pressure or
capillary forces .
Apart from the mount described with reference to Figs. 2a
to 2d an automatic mount can be provided, which allows
automatic adjustment of the position of the displacer to
the fluid conduct, for example in response to a signal
indicating dosing volume range or a desired
dosing volume, respectively.
By using the inventive microdosing apparatuses, thus,
individual free flying microdroplets are generated
preferabl'.' at an outlet openinq in contact with the
surrounding atmosphere, to dispense fluid as free living
droplets or free flying jet at the outlet opening. Thereby,
the present invention allows ejecting of a droplet already
with a single operating cycle of the actuating device,

volume of the fluid conduit to thereby eject the droplet.
The present invention allows adjusting the dosing volume by
adjusting the hub of the actuating device and/or disposing
the actuating device at a predetermined position along the
adapted axial length can be chosen.
When using an adjustable hub for adjusting the dosing
volume, the hub h of the actuating de-vice or the displacer,
respectively, is variable and smaller than the diameter of
the tube, i.e. the cross section dimension of the same in
actuating device.
In the case where the whole tube cross section is crimped,
i.e. the flow area is substantially brought to zero, as
required in DE 4.31434 3 C2, the drop volume is determined by
tube diameter. By crimping the tube, the whole volume
within the relevant tube portion is displaced.
Approximately, for the displaced volume which then
significantly determines the drop volume with otherwise
equal arrangement- the following applies:

Here, 7 represents the displaced volume, a the length of
the displacer and d the diameter of the tube.
Compared with this, in a displacer with adjustable hub, the
role. Here, the displaced volume depends on the hub h and
can be approximately be described by the volume of a
laterally trimmed cylinder:

Here, h is the distance by which the tube is compressed.
by this dependence the displaced volume on hub h and
its described effect on the drop volume, the present
invention allows a variable adjustment of the dosing volume
without having to connect a tube with different diameter or
a displacer with different dimensions, respectively.
According to the invention, there is a connection between
volume displacement and drop generation or drop volume,
respectively, in a single dosing process, so that the
present invention allows dosing with a non-periodic
excitation. This is advantageous, for example, when
specific non-periodic patterns are to be printed on 3
In the above-described embodiments, the actuating device is
designed to effect an actuation of the tube starting from
are possible where the tube is partly or fully crimped,
i.e. compressed, in standby mode. A schematic cross section
representation of such an embodiment is shown in Fig. 10a.
The tube 100 is applied to a counter mount 300 at its
backside. On the opposing side of the tube 100, a
piezoactuator 301' is mounted to a mount 302 of an actuating
device. A displacer 306 is disposed at the front end of the
piezoactuator 302 .
In the arrangement shown in Fig. 10a, the tube 100 is fully
crimped in the standby mode. The dosing cycle starts with
slowly pulling back the plezoactuator 302, so that the
cross section of the tube 100 is partly freed. During this
phase, fluid flows from the reservoir, to which the tube
100 is connected at the end 102 opposing the outlet opening

104, in the previously crimped area, in order to compensate
the increasing tube volume. The actual dosing process with
the drop formation at the outlet end 104 is then performed
by quickly extending the piezoactuator 302 to decrease the
tube volume again. As in the above-described embodiments,
the dosed volume is defined by the adjustment travel of the
piezoactuator 302 and can thus be controlled by varying the
operating voltage or by the variation of the charging
current or discharge current at the piezoactuator 302,
respectively. It is an advantage of the configuration shown
in Fig. l0a that the crimped tube has a significantly lower
evaporation rate of dosed material compared to the normally
open tube.
Thus, this embodiment contains an integrated closing
mechanism. However, it is a disadvantage that in
commercially available conventional piezostack actuators
the extended state of the piezoactuator is that state where
the electric voltage is applied. When taking away the
electric voltage, the piezostack actuator becomes shorter,
the reduced state. Accordingly, this means that the
embodiment of an integrated closing mechanism snown in Fig.
10a effects a continuous but slight energy consumption. In
order to fully use the advantages of the integrated closing
mechanism, it is advantageous in the embodiment shown in
Fig. 10a to apply an electrical voltage continuously or to
dosing system is not used.
An integrated closing mechanism with reduced energy
consumption can be implemented by providing the actuating
device with a biasing means, for example a spring, pressing
the displacer against the polymer tube in order to achieve
partial or full crimping of the tube in the standby mode.
Then, the actuating device preferably has an actuator,
which is disposed to move the displacer against the force
of the biasing means and to release the tube cross section
partly or fully.

An embodiment tor such an integrated closing mechanism is
shown in Fict. 10b. Again, the tube 100 is applied against a
counter mount 310. In this embodiment, an actuating device
comprises combination of a sprinq 312 and a piezostack
actuator 31-1. Further, the actuating device comprises a
displacer 31c, which is rigidly coupled to an actuating
plate 318. In Fig. 10b, two couplings rods 320 and 322 are
shown as exemplary coupling means. The spring 312 is
presses the displacer 316 against tube 100 to crimp the
same in the non-operated state of the actuator 31-1. This
embodiment allows the realization of a dosing apparatus
whose tube is crimped with switched off electrical supply
voltage, so that the same has an integrated closing
mechanism without continuous energy consumption.
In the off state, the displacer 316 is pressed on
to the tube 100 by the spring such that the same is pressed
onto the counter mount 310 and crimped. If a dosing process
is to be performed, the piezoactuator 314 is extended by
applying an electrical voltage, and thus the displacer 316
is reset against the sprinq force. The tube relaxes and the
liquid to be dosed flows in from the reservoir connected to
the side 102 of the tube opposed to the outlet opening 10-J.
By quickly driving back the piezostack actuator 318, the
tube 100 is again crimped via the spring 312, which is
dimensioned in a sufficiently strong way. The spring is
dimensioned rigidly enough so that liquid is dispensed from
the outlet opening 10-1 as free flying jet. The dosed volume
is again defined by the adjustment travel of the
piezoactuator and can thus be controlled be varying the
operating voltage or by varying the charging or discharge
current in the piezostack actuator, respectively.
Here, it should be noted that embodiments discussed with
regard to FIGS. 10a and 10b also function when the tube is
not fully.

In the embed i mentis of the present invention, where the
dosing volume is adjusted via the adjustable hub of the
displacer or the actuating device, respectively, the
displacer is moved between a first end position and the
second end position, wherein the polymer tube is partly
compressed in the first end position and the second end
position. Thereby, the first end position defines a larger
tube volume than the second end position, so that by moving
the displacer from the first end position, into the second
end position liquid is dosed out of the ejection end.
Thereby, the first end position can define a fully relaxed
state of the tube or a partly compressed state of the same.
The second end position can comprise a partly compressed
state or a fully compressed state of the polymer tube, in
other words, in the inventive embodiments, where the dosing
volume is adjustable by an adjustable hub of the actuating
device, the tube wall is moved by the actuating device or
by the dispiacer, respectively, 'via a part of the light
cross section of the flexible polymer tube. In contrary,
when fully crimping the tube from a non-crimped state to a
fully crimped state, the tube wall is moved across the
whole light cross section of the tube.
The embodiments shown in Figs. 10a and 10b can also be
implemented such that the position of the actuating device
can be varied to thereby be able to vary the dosing volume
dispensed from the cutlet opening.

WE CLAIM:
1. A microdosing apparatus, comprising:
a fluid conduit (100; 150) having a flexible tube with a first end (102) for
connecting to a liquid reservoir (200) and a second end where an outlet
opening (10) is located; and
an actuating device having a displacer (108; 108'; 208; 306; 316) with
adjustable hub, by which the volume of a portion of the flexible tube can
be changed, to thereby dispense liquid as free flying droplets or as free
flying jet at the outlet opening (104) by moving the displacer (108; 108';
208; 306; 316) between a first end position and a second end position,
wherein the tube is partly compressed at least in the first end position or
the second end position.
2. The microdosing apparatus as claimed in claim 1, wherein the flexible
tube consists of polyimide.
3. The microdosing apparatus as claimed in claim 1 or 2, wherein the
flexible tube has at least one portion wherein the same has no erratic
cross section changes, so that by changing the position of the actuating
device (108; 108'; 164; 208) along the portion, a ratio of a fluidic
impedance between the position of the actuating device and the outlet
opening (104) to a fluidic impedance between the first end (102) and the

position of the actuating device is variable, so that the liquid volume
output at the outlet opening (104) is variable by at least 10%.
4. The microdosing apparatus as claimed in one of claim 1 to 3, wherein the
tube can be compressed across a predetermined length by the displacer
(108; 108'; 208; 306; 316) in order to effect the volume change of the
tube.
5. The microdosing apparatus as claimed in claim 4, wherein the displacer
(108) has a form to effect an axially asymmetric volume change with
regard to the tube.
6. The microdosing apparatus as claimed in one of claims 1 to 5, comprising
means (150, 152, 162) for holding the actuating device at one or the
position along the tube.
7. The microdosing apparatus as claimed in one of claims 1 to 6, comprising
a biasing means (312), to bias the tube into a fully or partly compressed
state through a displacer (316).
8. The microdosing apparatus as claimed in claim 7, wherein the actuating
device has an actuator (314, 320, 322), which is disposed to move the
displacer (316) against the bias of the biasing means (312).
9. A microdosing apparatus, comprising:

a fluid conduit (100; 150) with a first end (102) for connecting to a fluid
reservoir (100) and a second end where an outlet opening (104) is
located, the fluid conduit (100; 150) having a portion along which a cross
section of the fluid conduit can be varied to effect a change of the volume
of the fluid conduit;
an actuating device (108'; 164; 208) disposed at a position along the
portion of the fluid conduit for effecting a change of the volume of the
fluid conduit to thereby dispense liquid as free flying droplets or free
flying jet from the outlet opening (104),
wherein a ratio of a fluidic impedance between the position of the
actuating device (108; 108;; 164; 208) and the outlet opening (104) to a
fluidic impedance between the first end (102) and the fluid conduit (100;
150) and the position of the actuating device is variable by changing the
position of the actuating device, so that a volume dispensed at the outlet
opening (104) is thereby variable by at least 10%.
10. The microdosing apparatus as claimed in claim 9, wherein the actuating
device has a displacer (108; 108'; 164; 208) by which the portion of the
fluid conduit (100; 150) can be compressed across a predetermined
length to effect the volume change of the portion of the fluid conduit.
11. The microdosing apparatus as claimed in claim 10, wherein the displacer
(108) has a form to effect an axially asymmetric volume change with
regard to the portion of the fluid conduit (100; 150).

12. The microdosing apparatus as claimed in one of claims 9 to 11,
comprising means (150, 152, 162) for holding the actuating device at the
position along the portion of the fluid conduit.
13. The microdosing apparatus as claimed in one of claims 1 to 12, wherein
the fluid conduit (100; 150) has no erratic cross section changes between
the first end (102) and the outlet opening (104) in the resting state.
14. The microdosing apparatus as claimed in one claims 1 to 12, wherein the
fluid conduit (100; 150) has a substantially constant cross section
between the first end (102) and the outlet opening (104) in the resting
position.
15. The microdosing apparatus as claimed in one of claims 1 to 14,
comprising means for providing the fluid conduit with a pressure
difference.
16. The microdosing apparatus as claimed in one of claims 1 to 15, wherein
the fluid conduit (100; 150) has such a cross section area that a liquid to
be dosed can be moved through the same by capillary forces.
17. The microdosing apparatus as claimed in one of claims 1 to 16,
comprising a plurality of respective fluid conduits, so that several equal or
different liquids can be dispensed simultaneously or successively.

18. The microdosing apparatus as claimed in claim 17, comprising an
actuating device for simultaneously effecting the volume change of the
plurality of fluid conduits.
19. The microdosing apparatus as claimed in claim 18, wherein the actuating
device is a common displacer.
20. A method for dispensing a desired volume of liquids in a microdosing
apparatus, the method comprising the steps of:
filling a fluid conduit (100; 150) having a flexible tube with a liquid to be
dispensed; effecting a volume change of a portion of the flexible tube by
a displacer (108; 108'; 208; 306; 316) with adjustable hub, to thereby
dispense liquid as free flying droplets or as free flying jet at an outlet
opening (104) of the fluid conduit (100; 150) by moving the displacer
(108; 108'; 208; 306; 316) between a first end position and a second end
position, wherein the tube is partly compressed at least in the first end
position or the second end position.
21. The method as claimed in claim 20, comprising the step of providing a
displacer (108; 108'; 164; 208) at a position along the tube, by which the
tube can be compressed across a predetermined length to effect the
volume change of the portion of the same.

22. The method as claimed in claim 21, wherein the fluid conduit (100; 150)
has a first end (102) connected to a fluid reservoir (200) and a second
end where the outlet opening (104) is located, comprising the step of:
selecting the position of the displacer along the tube to adjust a ratio of a
fluidic impedance between the position of the displacer (108; 108'; 164;
208) and the outlet opening (104) to a fluidic impedance between the
first end (102) and the position of the actuating device, to thereby
dispense a desired liquid volume at the outlet opening (104) by effecting
the volume change.
23. The method as claimed in claim 21 or 22, comprising a step of selecting a
displacer (108; 108'; 164; 208) with a length axial with regard to the
flexible tube, to effect the volume change by using the displacer and to
dispense a desired liquid volume at the outlet opening (104).
24. The method as claimed in one of claims 22 to 23, wherein in the step of
effecting the volume change, a volume change axially asymmetric with
regard to the flexible tube is performed to effect a fluid flow with a
preferred direction towards the outlet opening (104) in the fluid conduit
(100; 150).
25. The method as claimed in one of claims 20 to 24, comprising a step of
providing the fluid conduit (100; 150) with a static pressure.

26. The method as claimed in claim 25, wherein the static pressure with
regard to the outlet end is an overpressure to effect a fluid flow with a
preferred direction towards the outlet opening (104) when effecting the
volume change in the fluid conduit (100; 150), and/or to support a refill
after a dispensing process.
27. The method as claimed in claim 25, wherein the static pressure with
regard to the outlet end is a subpressure to prevent leaking of liquid from
the outlet end when no volume change is effected.
28. The method as claimed in one of claims 20 to 27, comprising a step of
reversing the volume change after the step of effecting a volume change,
so that the tube returns to the initial state, wherein during this step a
capillary refill of the fluid conduit (100; 150) takes place.
29. A method for dispensing a desired volume of a liquid in a dispensing
process adapting a microdosing apparatus as claimed in claim 10, the
method comprising the step of:
disposing the actuating device (108; 108'; 164) at a predetermined
position along the portion of the fluid conduit (100; 150), so that due to
the resulting ratio of fluidic impedances in the step of effecting a change
of the volume of the liquid conduit (10; 150), a desired liquid volume can
be dispensed at the outlet opening (104).

30. A method for dispensing a desired volume of a liquid in a dispensing
process adapting a microdosing apparatus, the method comprising the
step of:
selecting a displacer (108; 108'; 164; 208) with an axial length (11, 12)
with regard to the portion of the fluid conduit (100; 150), which is
adapted to allow dispensing of a desired volume at the outlet opening
(104) in the step of effecting a change of the volume of the liquid conduit
(100; 150).

The invention relates to a microdosing apparatus, comprising a fluid conduit
(100; 150) having a flexible tube with a first end (102) for connecting to a liquid
reservoir (200) and a second end where an outlet opening (10) is located; and
an actuating device having a displacer (108; 108'; 208; 306; 316) with
adjustable hub, by which the volume of a portion of the flexible tube can be
changed, to thereby dispense liquid as free flying droplets or as free flying jet at
the outlet opening (104) by moving the displacer (108; 108'208; 306; 316)
between a first end position and a second end position, wherein the tube is
partly compressed at least in the first end position or the second end position.

Documents:

299-kolnp-2006-granted-abstract.pdf

299-kolnp-2006-granted-claims.pdf

299-kolnp-2006-granted-correspondence.pdf

299-kolnp-2006-granted-description (complete).pdf

299-kolnp-2006-granted-drawings.pdf

299-kolnp-2006-granted-examination report.pdf

299-kolnp-2006-granted-form 1.pdf

299-kolnp-2006-granted-form 18.pdf

299-kolnp-2006-granted-form 2.pdf

299-kolnp-2006-granted-form 26.pdf

299-kolnp-2006-granted-form 3.pdf

299-kolnp-2006-granted-form 5.pdf

299-kolnp-2006-granted-reply to examination report.pdf

299-kolnp-2006-granted-specification.pdf

299-kolnp-2006-granted-translated copy of priority document.pdf

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Patent Number

227608

Indian Patent Application Number

299/KOLNP/2006

PG Journal Number

03/2009

Publication Date

16-Jan-2009

Grant Date

14-Jan-2009

Date of Filing

10-Feb-2006

Name of Patentee

ROLAND ZENGERLE

Applicant Address

AM SCHANZLE 3 79183 WALDKIRCH

Inventors:

#	Inventor's Name	Inventor's Address
1	ROLAND ZENGERLE	AM SCHANZLE 3 79183 WALDKIRCH
2	PETER KOLTAY	BENZHAUSERSTR.5, 79232 MARCH
3	WOLFGANG STREULE	TALSTR. 21 79183 WALDKIRCH
4	GERHARD BIRKLE	JOHANN-SEBASTIAN-BACH-STR. 14 79104 FREIBURG

PCT International Classification Number

B01L 3/02

PCT International Application Number

PCT/EP2004/009063

PCT International Filing date

2004-08-12

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	103 37 484.1-52	2003-08-14	Germany