Capillary microvalve

Abstract

The invention provides microvalves for controlling fluid flow from microreservoirs into transfer channels using capillary valving mechanisms. This invention provides microvalving means for use in apparatus useful for performing microanalytic and microsynthetic analyses and procedures, such as microminiaturization of genetic, biochemical and chemical processes related to analysis, synthesis and purification of biological, chemical, environmental and other compounds.

We claim:  
     
         1 . A capillary valve in a fluidic microchannel wherein the microchannel comprises a first portion of an interior wall having a first contact angle with a fluid contained therein and a second portion of the interior wall having a second contact angle with a fluid contained therein, wherein the contact angle in the first portion of the interior wall permits fluid to flow through a section of the microchannel bounded by the first portion of the interior wall when the fluid is propelled through the microchannel at a first pressure but the contact angle in the second portion of the interior wall does not permit fluid to flow through a section of the microchannel bounded by the second portion of the interior wall unless the fluid is propelled through the microchannel at a second pressure that is greater than the first pressure, thereby forming a capillary valve in the microchannel.  
     
     
         2 . A capillary valve according to  claim 1 , wherein fluid is propelled through the microchannel by centripetal force.  
     
     
         3 . A capillary valve according to  claim 2 , wherein the first pressure that does not permit fluid to flow past the capillary valve is increased to the second pressure propelling the fluid through the microchannel that permits fluid to flow past the capillary valve by increasing the speed of rotation of a platform comprising the microchannel.  
     
     
         4 . A capillary valve according to  claim 1  wherein the second contact angle is greater than 90 degrees.  
     
     
         5 . A capillary valve according to  claim 1 , wherein the first contact angle in the first portion of the interior wall of the microchannel is less than 90 degrees.  
     
     
         6 . A capillary valve according to  claim 1 , wherein the first contact angle in the first portion of the interior wall of the microchannel and the second contact angle are greater than 90 degrees and the second contact angle is greater than the first contact angle.  
     
     
         7 . A capillary valve according to  claim 1 , wherein the first contact angle in the first portion of the interior wall of the microchannel and the second contact angle in the second portion of the interior wall of the microchannel differ by treating the interior wall of the second portion of the interior wall of the microchannel with a substance that increases the contact angle of said second portion of the interior wall of the microchannel.  
     
     
         8 . A capillary valve according to  claim 1 , wherein the first contact angle in the first portion of the interior wall of the microchannel and the second contact angle in the second portion of the interior wall of the microchannel differ due to a difference in the substrate comprising the first and second portions of the interior wall of the microchannel with a substance that increases the contact angle of said second portion of the interior wall of the microchannel.  
     
     
         9 . A capillary valve according to  claim 1 , wherein the first contact angle in the first portion of the interior wall of the microchannel and the second contact angle in the second portion of the interior wall of the microchannel differ by a difference in cross-sectional diameter of the first portion of the microchannel and the cross-sectional diameter of the second portion of the second portion of the interior wall of the microchannel.  
     
     
         10 . A capillary valve according to  claim 1 , wherein the first portion of the interior wall of the microchannel is wettable and the second portion of the interior wall of the microchannel is non-wettable.  
     
     
         11 . A capillary valve according to  claim 1  wherein the fluidic microchannel connects a first and a second fluid reservoir on a microsystems platform.  
     
     
         12 . A capillary valve according to  claim 11  wherein the first portion of the interior wall of the microchannel is closer to the axis of rotation of the microsystems platform than is the second portion of the interior wall of the microchannel.  
     
     
         13 . A capillary valve according to  claim 1  wherein the second portion of the interior wall of the microchannel comprises an annular ring.  
     
     
         14 . A capillary valve according to  claim 1  wherein the second portion of the interior wall of the microchannel comprises a patch.