Diffusion membrane micropump, device, and associated method

Abstract

The present invention is directed to pumps, device, and methods for handling liquids on a microscale. Specifically, a microfluidic pump is described in which liquid in a fluid microchannel may be moved in either direction due to the diffusion of a gas through a diffusion membrane in response to a pressure differential applied through a control microchannel. This pump can provide non-contact, and optionally, bi-directional movement of liquid in microfluidics platforms, as well as bubble-free filling of dead-end microchannels and reservoirs.

1 . A microfluidic pump, comprising:
 a) a diffusion membrane;   b) a control microchannel having an open end and a closed end, wherein the open end is in functional communication with a pressure source configured to produce a pressure change inside the control microchannel, and the closed end is defined at least in part by the diffusion membrane; and   b) a fluid microchannel having at least one open end, and configured to contain a volume of liquid, wherein the diffusion membrane is in communication with an interior of the fluid microchannel so that a pressure change produced by the pressure source induces a permeant gas to move through the diffusion membrane, thereby causing the liquid to move in a direction within the fluid microchannel.   
   
   
       2 . The microfluidic pump of  claim 1 , wherein the pressure source is configured to produce a positive pressure change inside the control microchannel sufficient to move the permeant gas from the control microchannel across the diffusion membrane into the fluid microchannel, thereby pushing the liquid away from the diffusion membrane. 
   
   
       3 . The microfluidic pump of  claim 1 , wherein the pressure source is configured to produce a negative pressure change inside the control microchannel sufficient to move permeant gas from the fluid microchannel across the diffusion membrane into the control microchannel, thereby pulling the liquid toward the diffusion membrane. 
   
   
       4 . The microfluidic pump of  claim 1 , wherein the pressure source is also a source of permeant gas. 
   
   
       5 . The microfluidic pump of  claim 1 , wherein the diffusion membrane comprises polydimethylsiloxane. 
   
   
       6 . The microfluidic pump of  claim 1 , wherein the diffusion membrane has a thickness of from 5 μm to 200 μm. 
   
   
       7 . The microfluidic pump of  claim 6 , wherein the diffusion membrane has a thickness of from 20 μm to 120 μm. 
   
   
       8 . The microfluidic pump of  claim 1 , wherein the average rate of delivery of liquid to another point in the fluid microchannel is from 1 nl/min to 500 nl/min. 
   
   
       9 . The microfluidic pump of  claim 1 , wherein the average rate of delivery of liquid to another point in the fluid microchannel is from 10 nl/min to 200 nl/min. 
   
   
       10 . The microfluidic pump of  claim 1 , wherein the liquid is not in physical contact with the diffusion membrane. 
   
   
       11 . The microfluidic pump of  claim 1 , wherein the device is configured for generating bi-directional flow of the volume of liquid. 
   
   
       12 . The microfluidic pump of  claim 11 , wherein the bi-directional flow is generated by providing a vacuum in the fluid microchannel to drive the volume of liquid in a first direction, and providing increased pressure in the fluid microchannel to drive the volume of liquid in a second direction. 
   
   
       13 . The microfluidic pump of  claim 1 , wherein the volume of liquid is moved without a peristaltic pump. 
   
   
       14 . A microfluidic device, comprising
 a) one or more microfluidic pumps as in  claim 1 ;   b) one or more wells configured to receive liquid from outside the device to be delivered to the one or more microfluidic pumps; and   c) one or more wells configured to receive liquid from the one or more microfluidic pumps for retrieval from the device.   
   
   
       15 . A microfluidic device as in  claim 14 , wherein the device is formed of a material including a member selected from the group consisting of glass, polydimethylsiloxane, photoresist, hydrogel, thermoplastic, and combinations thereof. 
   
   
       16 . A method of moving liquid in a fluid microchannel, comprising:
 a) providing a fluid microchannel which includes an open end and a closed end, said fluid microchannel containing a volume of liquid and a volume of permeant gas at least substantially sealed between the closed end and the volume of liquid, wherein an inner surface of the fluid microchannel proximate the volume of permeant gas is in fluid communication with a diffusion membrane; and   b) removing at least a portion of the volume of permeant gas out of the fluid microchannel through the diffusion membrane, thereby causing the volume of liquid to move due to negative pressure created by removing the portion of the volume of permeant gas.   
   
   
       17 . The method of  claim 16 , wherein the step of removing the at least a portion of the volume of permeant gas further includes dead end channel filling the fluid microchannel with the volume of liquid such that the closed end of the fluid microchannel is substantially free from bubbles of the permeant gas. 
   
   
       18 . The method of  claim 16 , wherein the diffusion membrane comprises polydimethylsiloxane. 
   
   
       19 . The method of  claim 16 , wherein the diffusion membrane has a thickness of from 5 μm to 200 μm. 
   
   
       20 . The method of  claim 16 , wherein the diffusion membrane has a thickness of from 20 μm to 120 μm. 
   
   
       21 . The method of  claim 16 , wherein the average rate of delivery of liquid to another point in the fluid microchannel is from 1 nl/min to 500 nl/min. 
   
   
       22 . The method of  claim 16 , wherein the average rate of delivery of liquid to another point in the fluid microchannel is from 10 nl/min to 200 nl/min. 
   
   
       23 . The method of  claim 16 , wherein the volume of liquid is moved without a peristaltic pump.