Title of Invention

A MONOLITHIC POLYMERIC FILTER MEMBRANE AND A METHOD FOR MAKING THE SAME

Abstract

A filter membrane, methods of making such filter membrane and apparatus employing such filter membrane are disclosed, in which the filter membrane is a monolithic polymeric membrane (20) that includes a polymeric filter layer (22) including a micro-scale precision-shaped pores (24) and a polymeric support layer (26) that has a precision-shaped porous support for the filter layer. Several methods are disclosed for making such a membrane using micromachining technique, including lithographic, laser ablation and x-ray treatment techniques. Several filter apparatuses employing such a membrane are disclosed.

Full Text

FORM 2 THE PATENTS ACT, 1970 [39 OF 1970] THE PATENTS RULES, 2003 COMPLETE SPECIFICATION [See Section 10; rule 13] "A MONOLITHIC POLYMERIC FILTER MEMBRANE AND A METHOD FOR MAKING THE SAME" BAXTER INTERNATIONAL INC., a Delaware corporation, of One Baxter Parkway, Deerfield, Illinois, 60015, United States of America, The following specification particularly describes the nature of the invention and the manner in which it is to be performed:- The present invention relates to a monolithic polymeric filter membrane and a method for making the same. The present invention relates generally to microporous membranes, to methods for making microporous membranes and to filtration or separation apparatus employing microporous membranes. More specifically, the present invention relates to microporous membranes of the type employing precisely dimensioned, micron-scale pores, and- to methods for making such membranes and apparatus employing such membranes. Background Filters that discriminate based on size and/or shape are well known. One type of filter, for example, provides a tortuous path through which particles must navigate to pass through the filter. These are sometimes referred to as depth filters, and typically use a filter element made of a thick bed of fiber or other material. Due to their thickness and tortuous path filtration technique, these filters sometimes require relatively high transmembrane, i.e. transfilter, pressures to facilitate flow through the filter, due to its thickness and the tortuous path filtration technique. In contrast to depth filters, another well-known type of filter employs relatively thin filter membranes, which typically have nominal pore sizes. Such membranes have been used in a wide variety of medical and industrial applications. For example, such filter membranes, with nominal pore size as low as 0.22 microns, have been used to filter bacteria and other matter from liquids, such as intravenous solutions. Such microporous WE CLAIM: 1. A monolithic polymeric filter membrane comprising: (a) a polymeric filter layer having micron-scale precision-shaped pores and (b) a polymeric support layer having a precision-shaped porous support structure for the filter layer. 2. The filter membrane as claimed in claim 1, wherein the support layer is thicker than the filter layer. 3. The filter membrane as claimed in claim 2, wherein the support layer is thicker than the filter layer by a factor of between 2 and 250. 4. The filter membrane as claimed in claim 1, wherein the support layer is coextensive with the filter layer. 5. The filter membrane as claimed in claim 1, wherein the support layer has at least two sublayers, a first sublayer of a selected porosity and a second sublayer of different porosity than the first sublayer and disposed between the first sublayer and the filter layer. 6. The filter membrane as claimed in claim 1, wherein the support structure has a first plurality of spaced apart support struts, the being spaced apart a distance greater than the size of the micron-scale pores. The filter membrane as claimed in claim 6, wherein the support structure has a second plurality of spaced apart support struts, the second plurality of struts intersecting the first plurality of struts to define a support grid. The filter membrane as claimed in claim 6 or 7, wherein the struts are spaced apart a distance in the range of 50 to 1000 microns. The filter membrane as claimed in claim 6 or 7, wherein the struts are between 10 and 100 microns in width. The filter membrane as claimed in claim 1, wherein the support structure has a support grid. The filter membrane as claimed in claim 10, wherein the support grid has at least two subgrids, a first subgrid comprising struts of selected width and spaced apart a selected distance and a second subgrid disposed between the first subgrid and the filter layer, the second subgrid having support struts of different width or spacing than the struts in the first subgrid. The membrane as claimed in claim 10, wherein the grid has a plurality of intersecting walls, said walls being curved at least at the intersections. 13. The filter membrane as claimed in claim 12, wherein the grid has a plurality of intersecting walls defined by spaced apart, generally cylindrically or elliptically shaped pores. 14. The filter membrane as claimed in claim 1, wherein the filter layer and support layer are has of different materials that are sufficiently compatible to form a monolithic membrane. 15. The filter membrane as claimed in claim 1, wherein.the filter layer and the support layer are defined on opposite sides of a single film, the pores communicating with the porous support structure to allow the passage of filtrate therethrough. 16. The filter membrane as claimed in claim 1, wherein the filter layer and support layer are formed separately of the same material and joined together to form the monolithic membrane. 17. The filter membrane as claimed in claim 1, wherein the polymeric material of the filter layer is photosensitive, etchable or suitable for laser ablation or X-ray treatment, and the polymeric material of the support layer is photosensitive, etchable or suitable for laser ablation or X-ray treatment. 18. The filter membrane as claimed in claim 1, wherein the polymeric material of the filter layer is etchable, and the polymeric material of the support layer is photosensitive or suitable for laser ablation. 19. The filter membrane as claimed in claim 1, wherein the polymeric material of the filter layer and support layer is an etchable polyimide material. 20. The filter membrane as claimed in claim 1, wherein the polymeric material of the filter layer and the support layer has photosensitive polyimide material. 21. The filter membrane as claimed in claim 1, wherein the filter membrane is flexible. 22. The filter membrane as claimed in claim 21, wherein the filter membrane is sufficiently flexible to be disposed along a radius of curvature of at least one-half inch. 23. The filter membrane as claimed in claim 1, wherein the pore size is less than or equal to about 20 microns. 24. The filter membrane as claimed in claim 1, wherein the pore size is less than or equal to about 0.65 microns. The filter membrane as claimed in claim 1, wherein the pore size is less than or equal to about 0.22 microns. The filter membrane as claimed in claim 1, wherein the pore size is less than or equal to about 2 microns. The filter membrane as claimed in claim 1, wherein the pore size is less than or equal to about 0.08 microns. The filter membrane as claimed in claim 1, wherein said micron-scale precision-shaped pores are non-circular. The filter membrane as claimed in claim 28, wherein said pores are elongated. The filter membrane as claimed in claim 28, wherein the pores are sized and shaped to prevent the passage of human blood white cells and permit the passage of cells and platelets. A method for making a monolithic polymeric filter membrane comprising at least a filter layer having micron-scale precision-shaped pores and a support layer having a precision-shaped support structure for the filter layer, the method comprising: forming the filter membrane layer by removing selected material from one side of a polymeric film, to define the precision-shaped micron-scale pores of the filter layer; and forming the support structure layer by removing selected material from the other side of said membrane to define the precision-shaped porous support structure, the pores communicating with the porous support structure to allow the passage of filtrate therethrough. A method for making a monolithic polymeric filter membrane comprising at least a filter layer having micron-scale precision-shaped pores therethrough and a support layer having a porous support structure for said filter layer, the method comprising: forming the filter layer by removing selected material from a first polymeric film to define a plurality of micron-scale precision-shaped pores therethrough; forming the support structure layer by removing selected material from a second polymeric film to define a precision-shaped porous support structure; and joining the filter and support layers together in overlying relationship to form a monolithic filter membrane. The method as claimed in claim 31 or 32, wherein at least one of said filter layer and support layer is formed by: providing a polymeric film that is of polyimide material applying a metallic film to one surface of said polyimide film, applying a photoresist material to said metallic film, creating a first pattern on said photoresist layer to define micron scale pores or support structure and removing selected material from said photoresist layer; removing material from said metallic film in the areas where said photoresist material has been removed; and removing selected material from the polyimide film in the areas where the metallic film has been removed to define the pores or support structure; removing any remaining photoresist material and the metallic film from the polyimide film. The method as claimed in claim 31 or 32, wherein at least one of said filter layer and said support layer has a photoimageable polymeric film and the at least one layer is formed by exposing the film to light through a mask defining a pattern and removing selected portions of said polymeric film defined by pattern to form the pores or support layer. The method as claimed in claim 33, wherein said polymeric film is a negative-acting photoimagable film and said removing is carried out by removing the non-exposed portions of said film. 36. The method as claimed in claim 33, wherein said film is a positive-acting photoimagable film and said removing is carried out by removing the exposed portions of said film. 37. The method as claimed in claim 33, wherein the removing of selected material from the polyamide file in carried by dry etching. 38. The method as claimed in claim 31 or 32, wherein at least one of the steps of removing material has" ablating the film by laser or treating the film with ionizing radiation. 39. The method as claimed in claim 38, employing an excimer laser to ablate said film. 40. The method as claimed in claim 65 or 66, wherein the support layer is thicker than the filter layer. 41. The method as claimed in claim 40, wherein the support layer is thicker than the filter layer by a factor of between 2 and 250. 42. The method as claimed in claim 34, wherein a continuous web of the photoimageable polymeric film is continuously supplied and the pattern is progressively created on said film and selected material is progressively removed to define the pores or support structure. 43. The method as claimed in claim 31 or 36, wherein a continuous web of laser ablatable polymeric film is continuously supplied and selected material is progressively removed to define the pores or support structure. 44. The method as claimed in claim 34, wherein said photoimageable polymeric film has a polyimide. 45. The method as claimed in claim 31 or 32, wherein the support structure has first plurality of spread apart support struts in which said struts are spaced apart a distance greater than the size of said micron-scale pores. 46. The method as claimed in claim 45, wherein said support structure has a second plurality of spaced apart struts intersecting said first plurality of struts to define a support grid. 47. The method as claimed in claim 45, wherein said struts are spaced apart a distance in the range of 50 to 1000 microns. 48. The filter membrane as claimed in claim 45, wherein the struts are between 10 and 100 microns in width. 49. The method as claimed in claim 31 or 32, wherein the support structure has a grid. The method as claimed in claim 31 or 32, wherein the support structure has at least two sublayers, a first sublayer of a selected porosity and a second sublayer of different porosity than the first sublayer and disposed between the first sublayer and the filter layer. The method as claimed in claim 49, wherein the support grid has at least two subgrids, a first subgrid having struts of selected width and spaced apart a selected distance and a second subgrid disposed between the first subgrid and the filter layer, the second subgrid having support struts of different width or spacing than the struts in the first subgrid. The method as claimed in claim 49, wherein the grid has a plurality of intersecting walls, said walls being curved at least at the intersections. The method as claimed in claim 52, wherein the grid has a plurality of intersecting walls defined by spaced apart, generally cylindrically or elliptically shaped pores. The method as claimed in claim 32, wherein support structure layer is formed by removing material from two non-fully cured polymeric films, one film having material removed to define a support structure of selected porosity, and another film having material removed to define a support structure of greater porosity that the one film, said filter layers film and support films being bonded together to form an integral filter membrane. The method as claimed in claim 31 or 32, wherein the filter membrane is flexible. The method as claimed in claim 55, wherein the filter membrane is sufficiently flexible to be disposed along a radius of curative of 1/2 inch. A separator comprising: a housing including a fluid inlet and a first fluid outlet, a flow path defined in said housing between said inlet and said first outlet, a monolithic polymeric filter membrane as claimed in. claim 1, disposed in the flow path to allow filtrate to pass therethrough, such membrane comprising: a filter layer including micron-scale precision-shaped pores through which filtrate may pass, and a support layer including a precision-shaped porous support structure for the filter"layer. The separator claim 57, wherein the filter membrane is curved. The separator as claimed in claim 58, wherein the filter membrane is curved along a radius of curvature of at least about one-half inch. A separator as claimed in claim 57, having: the housing has a generally cylindrical interior surface; a rotor rotatably mounted within the housing and including a generally cylindrical outer surface spaced from the interior surface of the housing; a monolithic flexible polymeric membrane disposed on selected of the generally cylindrical outer surface of the rotor and the generally cylindrical interior surface of the housing; the flexible membrane comprising a filter layer including micron-scale precision-shaped pores and a support layer including a precision-shaped porous support layer for the filter layer; an inlet in the housing for introducing suspension into the space between the rotor and housing surfaces; a first outlet in the housing for removing a portion of the suspension from the space between the rotor and housing surfaces; and a second outlet communicating with the support layer of the membrane for removing any filtrate passing through the membrane. The separator as claimed in claim 60, wherein the membrane is curved to conform to the generally cylindrical surface of the rotor or housing on which it is disposed. The separator as claimed in claim 57 or 60, wherein the support layer is thicker than the filter layer. 63. The separator as claimed in claim 62, wherein the support layer is thicker than the filter layer by a factor of between 2 and 250. 64. The separator as claimed in claim 57 or 60, wherein which the support layer is substantially coextensive with the filter layer. 65. The separator as claimed in claim 57 or 60, wherein the support layer includes at least two sublayers, a first sublayer of a selected porosity and a second sublayer of different porosity than the first sublayer and disposed between the first sublayer and the filter layer. 66. The separator as claimed in claim 57 or 60, wherein the support structure comprises a first plurality of spaced apart support struts, the struts being spaced apart a distance substantially greater than the size of the micron-scale pores. 67. The separator as claimed in claim 66, wherein the support structure comprises a second plurality of spaced apart support struts, the second plurality of struts intersecting the first plurality of struts to define a support grid. 68. The separator as claimed in claim 66, wherein the struts are spaced apart a distance in the range of 50 to 1000 microns. 69. The separator as claimed in claim 66, wherein the struts are between 10 and 100 microns in width. 70. The separator as claimed in claim 57 or 60, wherem the support structure has a support grid. 71. The separator as claimed in claim 57, wherein the support ahs at least two subgrids, a first subgrid having struts of selected width and spaced apart a selected distance and a second subgrid disposed between the first subgrid and the filter layer, the second subgrid including support struts of different width or spacing than the struts in the first subgrid. 72. The separator as claimed in claim 70, wherein the grid has a plurality of intersecting walls, said walls being curved at least at the intersections. 73. The separator as claimed in claim 72, wherein the grid has a plurality of intersecting walls defined by spaced apart, generally cylindrically or elliptically shaped pores. 74. The separator as claimed in claim 57 or 60, wherein said pores are sized to separate red cells and white cells from plasma and platelets. 75. The separator as claimed in claim 57 or 60, wherein the filter layer and support layer are comprised of different materials that are sufficiently compatible to form a monolithic membrane. 76. The separator as claimed in claim 57 or 60, wherein the filter layer and the support layer are defined on opposite sides of a single, film, the pores communicating with the porous support structure to allow the passage of filtrate therethrough. 77. The separator as claimed in claim 57 or 60, wherein the same material and joined together to form the monolithic membrane. 78. The separator as claimed in claim 57 or 60, wherein the polymeric material of the filter layer is photosensitive, etchable or suitable for laser ablation or x-ray treatment, and the polymeric material of the support layer is photosensitive, etchable or suitable for laser ablation or x-ray treatment. 79. The separator as claimed in claim 57 or 60, wherein the polymeric material of the filter layer is etchable, and the polymeric material of the support layer is photosensitive or suitable for laser ablation or x-ray treatment. 80. The separator as claimed in claim 57 or 60, wherein the polymeric material of the filter layer and support layer is an etchable polyimide material. 81. The separator as claimed in claim 57 or 60, wherein the polymeric material of the filter layer and the support layer comprises photosensitive polyimide material. 82. The separator as claimed in claim 57 or 60, wherein the filter membrane is flexible. 83. The separator as claimed in claim 57 or 60, wherein the pore size is less than or equal to 20 microns. 84. The separator as claimed in claim 57 or 60, wherein the pore size is less than or equal to 0.65 microns. 85. The separator as claimed in claim 57 or 60, wherein pore size is less than or equal to 0.22 microns. 86. The separator as claimed in claim 57 or 60, wherein pore size is less than or equal to 2 microns. 87. The separator as claimed in claim 57 or 60, wherein pore size is less than 0.08 microns. 88. The separator as claimed in claim 57 or 60, wherein said micron-scale precision-shaped pores are non-circular. 89. The separator as claimed in claim 88, wherein said pores are elongated. 90. The separator as claimed in claim 88, wherein the pores are sized and shaped to prevent the passage of human blood white cells and permit the passage of red cells and platelets. Dated this 19th day of July, 2001. (RITUSHKANEGl) OF REMFRY & SAGAR ATTORNEY FOR THE APPLICANTS

Documents:

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in-pct-2001-00851-mum-cancelled pages(12-07-2005).pdf

in-pct-2001-00851-mum-claims(granted)-(12-07-2005).doc

in-pct-2001-00851-mum-claims(granted)-(12-07-2005).pdf

in-pct-2001-00851-mum-correspondence(31-12-2007).pdf

in-pct-2001-00851-mum-correspondence(ipo)-(27-12-2007).pdf

in-pct-2001-00851-mum-drawing(12-07-2005).pdf

in-pct-2001-00851-mum-form 1(19-07-2001).pdf

in-pct-2001-00851-mum-form 13(27-07-2007).pdf

in-pct-2001-00851-mum-form 19(28-04-2004).pdf

in-pct-2001-00851-mum-form 1a(12-07-2005).pdf

in-pct-2001-00851-mum-form 1a(27-07-2007).pdf

in-pct-2001-00851-mum-form 2(granted)-(12-07-2005).doc

in-pct-2001-00851-mum-form 2(granted)-(12-07-2005).pdf

in-pct-2001-00851-mum-form 3(19-07-2001).pdf

in-pct-2001-00851-mum-form 5(19-07-2001).pdf

in-pct-2001-00851-mum-form-pct-isa-210(12-07-2005).pdf

in-pct-2001-00851-mum-petition under rule 138(12-07-2005).pdf

in-pct-2001-00851-mum-power of authority(12-07-2005).pdf