Passive membrane microvalves

Abstract

An exemplary device and method for microfluidic transport is disclosed as providing inter alia a valve membrane sheet ( 400 ), an inlet channel ( 140 ) and an outlet channel ( 150 ). The valve membrane sheet effectively confines transport of fluid from the inlet channel to the outlet channel where fluid may be purged. The valve membrane sheet also generally provides means for preventing or otherwise substantially decreasing the incidence of purged fluid re-entering the inlet channel. Accordingly, the reduction of backflow generally tends to enhance overall pumping performance and efficiency. Disclosed features and specifications may be variously controlled, adapted or otherwise optionally modified to improve micropump operation in any microfluidic application. Exemplary embodiments of the present invention representatively provide for substantially self-priming micropumps that may be readily integrated with, for example, existing portable LTCC technologies for the improvement of device package form factors, weights and other manufacturing and/or device performance metrics.

We claim:  
     
         1 . A passive membrane valve for use with a microfluidic pump, said valve comprising: 
 a valve membrane sheet, an inlet channel and an outlet channel;    said inlet channel suitably adapted to receive fluid for transport across said valve membrane sheet;    said valve membrane sheet comprising an opening region and a valve seating region;    said valve membrane sheet effectively confining transport of fluid from said inlet channel to said outlet channel where fluid may be purged;    said valve membrane sheet comprising passive means for substantially restricting backflow of purged fluid back into said inlet channel wherein said valve seating region seats against a sealing element.    
     
     
         2 . The passive membrane valve of  claim 1 , wherein said means for restricting the backflow of purged fluid further comprises: 
 means for effectively unseating at least a portion of said valve membrane sheet from said sealing element when the direction of fluid pressure tends to flow fluid in a direction away from said inlet channel across said valve membrane sheet toward said outlet channel; and    means for effectively seating said valve membrane sheet against said sealing element when the direction of fluid pressure tends to flow fluid in a direction away from said outlet channel across said valve membrane toward said inlet channel.    
     
     
         3 . The passive membrane valve of  claim 2 , wherein said sealing element comprises a printed ring.  
     
     
         4 . The passive membrane valve of  claim 3 , wherein said printed ring comprises at least one of glass, silicone, silicone-based rubber, rubber and polymer.  
     
     
         5 . The passive membrane valve of  claim 2 , wherein said valve membrane sheet comprises at least one of an inorganic material, an organic material, a metal, a metal alloy, silicone, silicone-based rubber, rubber and polymer.  
     
     
         6 . The passive membrane valve of  claim 2 , further comprising means for retaining said valve membrane sheet between said inlet channel and said outlet channel.  
     
     
         7 . The passive membrane valve of  claim 2 , wherein said valve membrane sheet effectively confines transport of fluid from said inlet channel to said outlet channel by means of peripheral slits oriented normal to the direction of fluid transport.  
     
     
         8 . The passive membrane valve of  claim 7 , wherein said peripheral slits comprise said opening region.  
     
     
         9 . A microfluidic pumping system, comprising a passive membrane valve according to  claim 1  and at least one of a pump actuator and a piezoelectric actuator.  
     
     
         10 . The microfluidic pumping system of  claim 9 , wherein said means for restricting the backflow of purged fluid comprises: 
 means for effectively unseating at least a portion of said valve membrane sheet from said sealing element when the direction of fluid pressure tends to flow fluid in a direction away from said inlet channel across said valve membrane sheet toward said outlet channel; and    means for effectively seating said valve membrane sheet against said sealing element when the direction of fluid pressure tends to flow fluid in a direction away from said outlet channel across said valve membrane sheet toward said inlet channel.    
     
     
         11 . The microfluidic pumping system of  claim 9 , further comprising means for retaining said valve membrane sheet within a microfluidic channel.  
     
     
         12 . The microfluidic pumping system of  claim 9 , wherein said pump actuator comprises at least one of a unimorphic piezoelectric element and a bimorphic piezoelectric element.  
     
     
         13 . The microfluidic pumping system of  claim 9 , further comprising a plurality of microfluidic pumps in fluidic communication with each other.  
     
     
         14 . The microfluidic pumping system of  claim 13 , wherein said fluidic communication of said microfluidic pumps comprises at least one of a series configuration and a parallel configuration.  
     
     
         15 . A multilayer micropump device, comprising a substrate, the passive membrane valve according to  claim 1 , a pump actuator and a pumping cavity.  
     
     
         16 . The multilayer micropump of  claim 15 , wherein said substrate comprises at least one of ceramic, metal, glass, polymer and wood.  
     
     
         17 . The multilayer micropump of  claim 15 , wherein said means for restricting the backflow of purged fluid comprises means for effectively seating said valve membrane sheet against said sealing element when the direction of fluid pressure tends to flow fluid in a direction away from said outlet channel across said valve membrane sheet toward said inlet channel.  
     
     
         18 . The multilayer micropump of  claim 15 , wherein said pump actuator comprises at least one of a unimorphic piezoelectric element and a bimorphic piezoelectric element.  
     
     
         19 . A method of fabricating the multilayer micropump device of  claim 15 , comprising: 
 providing a plurality of substrate layers;    forming into said plurality of substrate layers a transport conduit and a cavity, said transport conduit and said cavity in microfluidic communication to define a fluid transport path and a pumping cavity respectively;    placing within said fluid transport path a passive membrane valve according to  claim 1;  and    laminating each of the plurality of substrate layers to form a substantially monolithic micropump device.    
     
     
         20 . The method of  claim 19 , wherein said substrate layers comprise at least one of ceramic, metal, glass, polymer and wood.  
     
     
         21 . The method of  claim 20 , wherein said step of providing ceramic layers further comprises the step of providing a plurality of green sheets comprised of a ceramic material dispersed in an organic binder.  
     
     
         22 . The method of  claim 21 , wherein the step of forming said channel and said cavity in said plurality of ceramic layers comprises at least one of mechanically punching and laser drilling into each ceramic layer.  
     
     
         23 . The method of  claim 22 , further comprising the step of sintering said ceramic layers to form said monolithic package.  
     
     
         24 . The method of  claim 23 , further comprising the step of providing a pumping actuator element on a surface of said monolithic package, said pumping actuator suitably adapted to exert a pumping force as a result of application of a voltage to the monolithic micropump package.  
     
     
         25 . The method  claim 23 , further comprising the step of providing a pumping actuator element embedded in said monolithic package, said pumping actuator suitably adapted to exert a pumping force as a result of application of a voltage to the monolithic micropump package.