Micro-channel chemical concentrator

Abstract

Apparatus and method for increasing the concentration of a chemical substance in a fluid comprise a micro-fluidic elongated channel formed in a substrate, with the channel being in fluid-flow communication with an ambient region along its elongated dimension. In general, the fluid includes first and second chemical substances having different vapor pressures. The apparatus includes an evaporation controller for increasing the evaporation rate of the fluid from the channel into the ambient region, thereby increasing the concentration of the higher vapor pressure (HVP) substance in the portion of the fluid remaining in the channel and increasing the concentration of the lower vapor pressure (LVP) substance in the portion of the fluid evaporated into the ambient region.

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         12 . Apparatus comprising 
 a first substrate including a serpentine first channel disposed toward one end thereof,    an input port for introducing fluid into said first channel, said fluid including a high vapor pressure first substance and a lower vapor pressure second substance,    a second substrate including a serpentine second channel disposed toward the opposite end thereof and further including a collection cavity in fluid-flow communication with said first and second channels,    a gas-permeable membrane disposed between said first and second substrates, said membrane being in fluid-flow communication with said first channel,    means for heating said fluid in said first channel to cause a portion of said fluid to evaporate and pass through said membrane into said cavity, and    means for cooling said fluid portion in said cavity to cause it to condense, said condensed fluid flowing into said second channel.    
     
     
         13 . The apparatus of  claim 12 , further including a coating formed on the surfaces of said channels.  
     
     
         14 . A method of altering the concentrations of a higher vapor pressure first substance and a lower vapor pressure second substance in a fluid, comprising the steps of: 
 (a) introducing the fluid into an input port of an elongated micro-fluidic channel, said channel being in fluid-flow communication with an ambient region along its elongated dimension,    (b) causing the fluid to flow along the channel and to exit from an output port, and    (c) increasing the evaporation rate of said fluid from said channel into said ambient region, thereby increasing the concentration of said second substance in the portion of said fluid remaining in said channel and increasing the concentration of said first substance in the portion of said fluid evaporated into said ambient region.    
     
     
         15 . The method of  claim 14 , further including the step of collecting and condensing the portion of said fluid that evaporates into said ambient region.  
     
     
         16 . The method of  claim 14 , wherein said evaporation rate increasing step includes heating the fluid in said channel.  
     
     
         17 . The method of  claim 16 , wherein said heating step operates in a pulsed mode.  
     
     
         18 . The method of  claim 14 , wherein said evaporation rate increasing step includes reducing the pressure of said ambient region.  
     
     
         19 . The method of  claim 14 , wherein step (c) includes the step of blowing gas across the interface between said fluid and said ambient region.  
     
     
         20 . The method of  claim 14 , wherein a gas-permeable membrane is disposed between said channel and said ambient region, said membrane confining said fluid to said channel but allowing said evaporated first substance to flow therethrough to said ambient region,  
     
     
         21 . The method of  claim 14 , further including the step of collecting the portion of said fluid remaining in said channel.