Fluid mixing in low aspect ratio chambers

Abstract

A method and system for performing mixing in a low volume, low aspect ratio microfluidic chamber ( 3 ) is described. Two or more mixing bladders ( 13,15 ) formed adjacent the microfluidic chamber are inflated and deflated in reciprocating fashion to cause inward and outward deflection of discrete regions of the chamber wall to mix fluid within the chamber. Mixing bladders are actuated by air or another gas, or by a liquid such as water, pumped in and out of the bladders with a pump which may be located remote from the microfluidic device including the microfluidic chamber. In an alternative embodiment, mixing is generated by applying alternating mechanical forces to a surface of a flexible chamber forming device. The microfluidic chamber may be a hybridization chamber formed on a microarray ( 25 ) slide with the use of a microarray interface device, or it may be a microfluidic chamber formed in various other types of microfluidic devices.

1 . A microfluidic device comprising: 
 a. at least one low aspect ratio chamber comprising: 
 i. two substantially parallel main walls;  
 ii. a perimeter wall forming a boundary of said chamber and defining a length and width of said chamber, said chamber being further bounded by said two main walls, the distance between said main walls being small with respect to the length of said chamber; and  
 iii. at least two flexible diaphragm regions located in said parallel main walls at opposite ends of said at least one chamber and adapted to flex inward and outward with respect to said chamber; and  
   b. at least one inlet port through which fluid may be introduced into said at least one low aspect ratio chamber, wherein said at least one inlet port is sealable to maintain a substantially constant volume within said chamber.    
     
     
         2 . The microfluidic device of  claim 1 , wherein said microfluidic device comprises a plurality of low aspect ratio chambers, wherein each of said low aspect ratio chambers comprises: 
 a. two substantially parallel main walls;    b. a perimeter wall forming a boundary of said chamber and defining a length and width of said chamber, said chamber being further bounded by said two main walls, the distance between said main walls being small with respect to the length of said chamber; and    c. at least two flexible diaphragm regions located in said parallel main walls at opposite ends of said at least one chamber.    
     
     
         3 . The microfluidic device of  claim 2 , wherein each of said at least two flexible diaphragm regions is located adjacent to a bladder connected to an external pressure source and adapted to flex inward or outward in response to pressure changes in said bladder, and wherein one said bladder is located adjacent to diaphragm regions of multiple chambers.  
     
     
         4 . The microfluidic device of  claim 1 , wherein said flexible diaphragm regions are separated by a region at least equal in area to one of said diaphragm regions.  
     
     
         5 . The microfluidic device of  claim 1 , wherein said flexible diaphragm regions displace between about 0.1% and about 50% of the volume of said chamber.  
     
     
         6 . The microfluidic device of  claim 1 , wherein said flexible diaphragm regions displace between about 1% and about 30% of the volume of said chamber.  
     
     
         7 . The microfluidic device of  claim 1 , wherein said microfluidic device further comprises a chemically active region on at least one of said parallel main walls, and wherein said flexible diaphragm regions are positioned so that they do not overlay said chemically active region.  
     
     
         8 . The microfluidic device of  claim 2 , wherein the ratio of the distance between said main walls to the length of said chamber is between about 1:300 and about 1:10,000.  
     
     
         9 . The microfluidic device of  claim 2 , wherein the ratio of the distance between said main walls to the length of said chamber is between about 1:100 and about 1:1,000.  
     
     
         10 . The microfluidic device of  claim 2 , wherein the distance between said main walls is between about 10 μm and about 50 μm.  
     
     
         11 . The microfluidic device of  claim 2 , wherein the distance between said main walls is between about 15 μm and about 30 μm.  
     
     
         12 . The microfluidic device of  claim 2 , wherein the distance between said main walls is between about 50 μm and about 300 μm.  
     
     
         13 . The microfluidic device of  claim 1 , wherein said at least two flexible diaphragm regions are located at opposite ends of one of said main walls.  
     
     
         14 . The microfluidic device of  claim 1 , wherein one flexible diaphragm region is located on one wall, and at least one other flexible diaphragm region is located on the other main wall.  
     
     
         15 . The microfluidic device of  claim 1 , wherein each of said at least two flexible diaphragm regions is located adjacent to a bladder connected to an external pressure source, and adapted to flex inward or outward in response to changes in pressure within said bladder.  
     
     
         16 . The microfluidic device of  claim 15 , wherein said pressure source changes the pressure of a gas or gaseous mixture within said bladder.  
     
     
         17 . The microfluidic device of  claim 15 , wherein said pressure source changes the pressure of a liquid within said bladder.  
     
     
         18 . The microfluidic device of  claim 1 , wherein each of said at least two flexible diaphragm regions is adapted to flex inward or outward in response to mechanical pressure delivered by a mechanical actuator.  
     
     
         19 . The microfluidic device of  claim 18 , wherein said mechanical actuator comprises a roller or a brayer.  
     
     
         20 . The microfluidic device of  claim 18 , wherein said mechanical actuator comprises mechanical feet adapted to alternately apply and release pressure to said flexible diaphragm regions.  
     
     
         21 . The microfluidic device of  claim 1 , wherein said device comprises a substantially rigid base material.  
     
     
         22 . The microfluidic device of  claim 21 , wherein said diaphragm regions are formed integrally with said substantially rigid base material.  
     
     
         23 . The microfluidic device of  claim 21 , wherein said diaphragm regions are formed by a method selected from molding, cutting, machining, printing methods, etching, vapor deposition, and embossing.  
     
     
         24 . The microfluidic device of  claim 21 , wherein said diaphragm regions are formed from flexible sheet material adhered to said substantially rigid base material.  
     
     
         25 . The microfluidic device of  claim 1 , wherein said device is formed from flexible material.  
     
     
         26 . The microfluidic device of  claim 25 , wherein said diaphragm regions are formed by a method selected from molding, cutting, machining, printing methods, etching, vapor deposition, and embossing.  
     
     
         27 . The microfluidic device of  claim 25 , wherein said diaphragm regions are formed from flexible sheet material adhered to said substantially rigid base material.  
     
     
         28 . The microfluidic device of  claim 1 , further comprising at least one outlet port through which fluid may escape from said at least one low aspect ratio chamber, wherein said at least one outlet port is sealable to maintain a substantially constant volume within said chamber.  
     
     
         29 . The microfluidic device of  claim 1 , further comprising a plurality of outlet ports through which fluid may escape from said at least one low aspect ratio chamber, wherein each said outlet port is salable to maintain a substantially constant volume within said chamber  
     
     
         30 . The microfluidic device of  claim 29 , wherein said chamber comprises a plurality of outlet regions tapering toward said outlet ports.  
     
     
         31 . A reaction chamber forming device comprising an open low aspect ratio chamber adapted to be sealed against a substrate, said chamber comprising: 
 a. at least one substantially planar main wall, comprising two flexible diaphragm regions adapted to flex inward and outward with respect to said chamber in response to applied pressure;    b. a perimeter wall forming a boundary of said chamber and defining a length and width of said chamber, the height of said perimeter wall defining the height of said chamber, said height of said chamber being small with respect to the length of said chamber, said height of said chamber being small with respect to the length of said chamber;    c. at least one inlet port through which fluid may be introduced into said chamber;    d. at least one outlet port through which fluid may be removed or released from said chamber; and    e. a gasket adapted to reversibly seal said open low aspect ratio chamber to a planar surface of a substrate bearing a sample to form a closed low aspect ratio chamber containing said sample and having one wall formed by said surface of said substrate.    
     
     
         32 . The microfluidic device of  claim 31 , wherein the height of said chamber is between about 10 μm and about 50 μm.  
     
     
         33 . The microfluidic device of  claim 31 , wherein the height of said chamber is between about 15 μm and about 30 μm.  
     
     
         34 . The microfluidic device of  claim 31 , wherein the height of said chamber is between about 50 μm and about 300 μm.  
     
     
         35 . The reaction chamber forming device of  claim 31 , further comprising at least one bladder adjacent to said main wall, wherein said main wall is adapted to flex inward and outward with respect to said chamber in response to inflation and deflation of said bladder.  
     
     
         36 . The reaction chamber forming device of  claim 31 , wherein said device comprises a substantially rigid base material.  
     
     
         37 . The reaction chamber forming device of  claim 36 , wherein said diaphragm regions are formed integrally with said substantially rigid base material.  
     
     
         38 . The reaction chamber forming device of  claim 37 , wherein said diaphragm regions are formed by a method selected from molding, cutting, machining, printing methods, etching, vapor deposition, and embossing.  
     
     
         39 . The reaction chamber forming device of  claim 37 , wherein said diaphragm regions are formed from flexible sheet material adhered to said substantially rigid base material.  
     
     
         40 . The reaction chamber forming device of  claim 31 , wherein said device comprises a base structure formed of flexible material.  
     
     
         41 . The reaction chamber forming device of  claim 40 , wherein said diaphragm regions are formed by a method selected from molding, cutting, machining, printing methods, etching, vapor deposition, and embossing.  
     
     
         42 . The reaction chamber forming device of  claim 40 , wherein said diaphragm regions are formed from flexible sheet material adhered to said base structure.  
     
     
         43 . The reaction chamber forming device of  claim 31 , wherein said microfluidic device comprises a plurality of open low aspect ratio chambers, wherein each of said open low aspect ratio chambers comprises: 
 a. a substantially planar main wall;    b. a perimeter wall forming a boundary of said chamber and defining a length and width of said chamber, the height of said perimeter wall defining the height of said chamber, said height of said chamber being small with respect to the length of said chamber;    wherein said gasket comprises a plurality of openings formed therethrough, each opening corresponding to one said chamber.    
     
     
         44 . The microfluidic device of  claim 43 , further comprising at least one bladder adjacent to the main walls of multiple said chambers, wherein said main walls are adapted to flex inward and outward with respect to said chambers in response to inflation and deflation of said bladder, wherein said at least one bladder is connected to an external pressure source and adapted to flex inward or outward with respect to said plurality of chambers in response to pressure changes in said bladder.  
     
     
         45 . The microfluidic device of  claim 31 , wherein the ratio of the distance between said main walls to the length of said chamber is between about 1:30 and about 1:10,000.  
     
     
         46 . The microfluidic device of  claim 31 , wherein the ratio of the distance between said main walls to the length of said chamber is between about 1:100 and about 1:1,000.  
     
     
         47 . The microfluidic device of  claim 31 , wherein the ratio of the distance between said main walls to the length of said chamber is between about 1:200 and about 1:300.  
     
     
         48 . The microfluidic device of  claim 31 , wherein said at least one outlet port is sealable to maintain a substantially constant volume within said chamber.  
     
     
         49 . The microfluidic device of  claim 31 , comprising a plurality of outlet ports through which fluid may escape from said at least one low aspect ratio chamber, wherein each said outlet port is sealable to maintain a substantially constant volume within said chamber.  
     
     
         50 . The microfluidic device of  claim 49 , wherein said chamber comprises a plurality of outlet regions tapering toward said outlet ports.  
     
     
         51 . A fluid handling device comprising: 
 a. low aspect ratio chamber formed in a base structure;    b. at least one inlet through which fluid can be introduced into said low aspect ratio chamber, wherein said at least one inlet is sealable to maintain a substantially constant volume within said chamber;    c. a first mixing bladder located at a first end of said chamber;    d. a first channel communicating with said first mixing bladder;    e. a second mixing bladder located at a second end of said chamber; and    f. a second channel communicating with said second mixing bladder;    wherein said first and second mixing bladders may be alternately and reciprocally inflated and deflated to produce movement of fluid within said chamber while maintaining said chamber at said substantially constant volume.    
     
     
         52 . The fluid handling device of  claim 5   1 , wherein said base structure is formed of flexible material.  
     
     
         53 . The fluid handling device of  claim 52 , wherein said first and second mixing bladders are formed from a layer of a flexible sheet material secured over recesses formed in said base structure.  
     
     
         54 . The fluid handling device of  claim 52 , wherein each of said first and second mixing bladders is formed from a separate diaphragm of a flexible sheet material secured over a recess formed in said base structure.  
     
     
         55 . The fluid handling device of  claim 52 , wherein each of said first and second mixing bladders is formed from a balloon-like structure separately formed and secured within said chamber.  
     
     
         56 . The fluid handling device of  claim 51 , wherein said base structure is formed of a rigid or semi-rigid material.  
     
     
         57 . The fluid handling device of  claim 56 , wherein said first and second mixing bladders are formed from a layer of a flexible sheet material secured over recesses formed in said base structure.  
     
     
         58 . The fluid handling device of  claim 56 , wherein each of said first and second mixing bladders is formed from a separate diaphragm of a flexible sheet material secured over a recess formed in said base structure.  
     
     
         59 . The fluid handling device of  claim 56 , wherein each of said first and second mixing bladders is formed from a balloon-like structure separately formed and secured within said chamber.  
     
     
         60 . The fluid handling device of  claim 56 , wherein said base structure is formed from at least two layers of rigid material secured together, and wherein each of said first and second mixing bladders comprises: 
 a. a diaphragm formed integrally with a layer of said base structure; and    b. a recess formed in a face of a layer of said base structure;    wherein said recess is enclosed by securing together two layers of said base structures.    
     
     
         61 . The fluid handling device of  claim 60 , wherein said diaphragm is formed by molding, cutting, machining, printing methods, etching, vapor deposition, and embossing.  
     
     
         62 . The fluid handling device of  claim 51 , wherein said first and second mixing bladders are inflated and deflated by gas pressure differentials transmitted via said first and second channels.  
     
     
         63 . The fluid handling device of  claim 5   1 , wherein said first and second mixing bladders are inflated and deflated by liquid pressure differentials transmitted via said first and second channels.  
     
     
         64 . A method of mixing fluid within a low aspect ratio chamber, said chamber comprising: 
 a. two substantially planar and substantially parallel main walls;    b. a perimeter wall forming a boundary of the low aspect ratio chamber and defining a length and width of said chamber, said chamber being further bounded by said two main walls, the distance between said main walls being small with respect to the length of said chamber; and    c. at least first and second flexible diaphragm regions located in at least one of said parallel main walls at opposite ends of said chamber;    d. at least first and second mixing bladders, one mixing bladder adjacent to each said flexible diaphragm region; and    e. an inlet port through which fluid may be introduced into said low aspect ratio chamber;    said method comprising the steps of: 
 i. loading a volume of fluid into said chamber via said inlet port;  
 ii. sealing said inlet port to retain said volume of fluid within said chamber;  
 iii. inflating said first mixing bladder to cause deflection of said first flexible diaphragm region into said chamber; and  
 iv. deflating said first mixing bladder to cause deflection of said first flexible diaphragm region out of said chamber;  
   wherein said volume of said chamber remains substantially constant during said steps of inflating and deflating said first mixing bladder.    
     
     
         65 . The method of  claim 64 , wherein steps iii) and iv) are repeated one or more times, and wherein each repetition of steps iii) and iv) comprises one mixing cycle.  
     
     
         66 . The method of  claim 65 , wherein each said mixing cycle has a cycle time of between about 5 seconds and about 3 hours.  
     
     
         67 . The method of  claim 65 , wherein each said mixing cycle has a cycle time of between about 5 seconds and about 1 minute.  
     
     
         68 . The method of  claim 64 , wherein said first mixing bladder is actively inflated and actively deflated.  
     
     
         69 . The method of  claim 64 , wherein said first mixing bladder is actively inflated and passively deflated.  
     
     
         70 . The method of  claim 64 , wherein said first mixing bladder is passively inflated and actively deflated.  
     
     
         71 . The method of  claim 64 , comprising the further step of alternately deflating said second mixing bladder to cause deflection of said second flexible diaphragm region out of said chamber as said first mixing bladder is inflated, and inflating said second mixing bladder to cause deflection of a second flexible diaphragm region into said chamber as said first mixing bladder is deflated.  
     
     
         72 . The method of  claim 71 , wherein said first and second mixing bladders are actively inflated and actively deflated.  
     
     
         73 . The method of  claim 71 , wherein said first and second mixing bladders are actively inflated and passively deflated.  
     
     
         74 . The method of  claim 71 , wherein said first and second mixing bladders are passively inflated and actively deflated.  
     
     
         75 . The method of  claim 71 , wherein said first and second mixing bladders are connected to inlet and outlet ends of a common pressure source.  
     
     
         76 . The method of  claim 71 , wherein said first and second mixing bladders are connected to separate pressure sources calibrated to produce equal and opposite pressures.  
     
     
         77 . The method of  claim 71 , wherein each of said first and second mixing bladders is switched alternately between a positive pressure source and a negative pressure source through the use of a valve.  
     
     
         78 . The method of  claim 64 , wherein said second mixing bladder is vented to the atmosphere, so that said second flexible diaphragm is permitted to passively deflect outward when said first flexible diaphragm is deflected inward, and passively deflect inward when said first flexible diaphragm is deflected outward.  
     
     
         79 . The method of  claim 64 , wherein said first and second mixing bladders are alternately and reciprocally switched between a positive pressure source and atmospheric pressure.  
     
     
         80 . The method of  claim 64 , wherein said first and second mixing bladders are alternately and reciprocally switched between a negative pressure source and atmospheric pressure.  
     
     
         81 . The method of  claim 64 , wherein said first and second mixing bladders are alternately and reciprocally switched between a positive pressure source and a negative pressure source.  
     
     
         82 . A fluid handling device comprising a low aspect ratio chamber, the low aspect ratio chamber comprising 
 a. a substantially planar first main wall;    b. a substantially planar second main wall positioned substantially parallel with respect to said first main wall; and    c. a perimeter wall bounding the region between said first and second main walls, the height of said perimeter wall defining a microscale distance between said first and second main walls that is significantly smaller than the length and width of said first and second main walls;    wherein edges of said first and second main walls are fixed with respect to said perimeter wall, wherein at least one said first and second main walls comprises a central wall region adapted to flex inward and outward with respect to said chamber, wherein inward flexing of said central wall region causes the distance between said first and second main walls to be less in the central wall region of said chamber than in a peripheral region adjacent said perimeter wall, and wherein outward flexing of said central wall region causes the distance between said first and second main walls to be greater in said central wall region than in said peripheral region.    
     
     
         83 . The device of  claim 82 , further comprising at least one pumping mechanism for pumping fluid back and forth alternately in a first direction and a second direction within said low aspect ratio chamber, wherein said at least one central wall region is flexed outward when fluid is driven in said first direction, causing fluid to move preferentially in the central region of said chamber, and wherein said at least one central wall region is flexed inward when fluid is driven in said second direction, causing fluid to move preferentially along the sides of said chamber, thereby producing circulating movement of said fluid within said chamber.  
     
     
         84 . The device of  claim 83 , wherein said at least one central wall region is flexed inward and outward actively by a displacement mechanism.  
     
     
         85 . The device of  claim 83 , wherein said at least one central wall region is flexed inward and outward passively by the force of the fluid as it is moved back and forth in said chamber by said pumping mechanism  
     
     
         86 . A method of mixing fluid within a microfluidic device comprising a substantially fixed volume low aspect ratio chamber, wherein at least selected regions of the wall of said device adjacent said chamber can be moved inward or outward with respect to said chamber, the method comprising the steps of: 
 a. filling said chamber with fluid;    b. sealing said chamber to retain fluid within said chamber;    c. pumping said fluid in a first direction within said chamber;    d. deflecting a central wall region off the wall of said device so that in at least a portion of said chamber, the height of said chamber is greater in the central wall region of said chamber than on the periphery of said chamber;    e. pumping said fluid in a second direction within said chamber;    f. deflecting a central wall region off the wall of said device so that in at least a portion of said chamber, the height of said chamber is less in the central wall region of said chamber than on the periphery of said chamber;    g. repeating steps c. through f. to generate circulating fluid movement within said chamber.    
     
     
         87 . A method of mixing fluid within a fluid-filled microfluidic device comprising a substantially fixed volume low aspect ratio chamber, wherein at least selected regions of the wall of said device adjacent said chamber can be moved inward or outward with respect to said chamber, the method comprising applying pressure alternately to movable wall regions on opposite ends of said chamber by a brayer, a roller, or mechanical feet.  
     
     
         88 . A microfluidic device comprising: 
 a. at least one low aspect ratio chamber comprising: 
 i. two substantially parallel main walls;  
 ii. a perimeter wall forming a boundary of said chamber and defining a length and width of said chamber, said chamber being further bounded by said two main walls, the distance between said main walls being small with respect to the length of said chamber;  
 iii. at least one flexible diaphragm region located in one of said parallel main walls adapted to flex inward and outward with respect to said chamber; and  
 iv. and least one vent, said vent being sufficiently long that fluid displaced by the inward and outward flexing of said at least one flexible diaphragm region can move up and down within said vent while remaining contained within said vent; and  
   b. at least one inlet port through which fluid may be introduced into said at least one low aspect ratio chamber.    
     
     
         89 . The device of  claim 82 , further comprising at least one displacement mechanism operably connected to the central wall region and at least one fluid injector operably connected to the low aspect ratio chamber, wherein when the central wall region is flexed outward, fluid moves preferentially in the central region of the chamber, and when the central wall region is flexed inward, fluid moves preferentially along the sides of the chamber, thereby allowing control over fluid movement within the chamber.  
     
     
         90 . The device of  claim 89 , wherein the displacement mechanism is capable of flexing at least one central wall region inward and outward.  
     
     
         91 . The device of  claim 89 , wherein the fluid injector is capable of driving fluid flow through the low aspect chamber.  
     
     
         92 . The device of  claim 89 , wherein the displacement mechanism is selected from the group consisting of one or more mechanical feet, one or more brayers and one or more injectors.  
     
     
         93 . The device of  claim 89 , wherein the fluid injector is selected from the group consisting of micropipette, pipette, microsyringe and syringe.  
     
     
         94 . The device of  claim 82 , further comprising at least one displacement mechanism operably connected to the central wall region capable of flexing at least one central wall inward and outward and at least one fluid injector operably connected to the low aspect ratio chamber capable of driving fluid flow through the low aspect ration chamber, wherein when the central wall region is flexed outward, fluid moves preferentially in the central region of the chamber, and when the central wall region is flexed inward, fluid moves preferentially along the sides of the chamber, thereby allowing control over fluid movement within the chamber.  
     
     
         95 . The device of  claim 82 , further comprising at least one displacement mechanism operably connected to the central wall region and at least one pump operably connected to the low aspect ratio chamber, wherein when the central wall region is flexed outward, fluid moves preferentially in the central region of the chamber, and when the central wall region is flexed inward, fluid moves preferentially along the sides of the chamber, thereby allowing control over fluid movement within the chamber.  
     
     
         96 . The device of  claim 95 , wherein the displacement mechanism is capable of flexing at least one central wall region inward and outward.  
     
     
         97 . The device of  claim 95 , wherein the pump is capable of driving fluid flow through the low aspect chamber.  
     
     
         98 . The device of  claim 95 , wherein the displacement mechanism is selected from the group consisting of one or more mechanical feet, one or more brayers and one or more pumps.  
     
     
         99 . The device of  claim 95 , wherein the pump is selected from the group consisting of micropipette, pipette, microsyringe and syringe.  
     
     
         100 . The device of  claim 95 , further comprising at least one displacement mechanism operably connected to the central wall region capable of flexing at least one central wall inward and outward and at least one pump operably connected to the low aspect ratio chamber capable of actuating fluid flow through the low aspect ration chamber, wherein when the central wall region is flexed outward, fluid moves preferentially in the central region of the chamber, and when the central wall region is flexed inward, fluid moves preferentially along the sides of the chamber, thereby allowing control over fluid movement within the chamber.