Microfabricated diffusion-based chemical sensor

Abstract

A channel-cell system is provided for detecting the presence and/or measuring the presence of analyte particles in a sample stream comprising: a) a laminar flow channel; b) two inlet means in fluid connection with said laminar flow channel for respectively conducting into said laminar flow channel (1) an indicator stream which may comprise an indicator substance which indicates the presence of said analyte particles by a detectable change in property when contacted with said analyte particles, and (2) said sample stream; c) wherein said laminar flow channel has a depth sufficiently small to allow laminar flow of said streams and a length sufficient to allow particles of said analyte to diffuse into said indicator stream to the substantial exclusion of said larger particles in said sample stream to form a detection area; and d) outlet means for conducting said streams out of said laminar flow channel to form a single mixed stream.

1 . A microfluidic device comprising: 
 (a) a microfluidic channel having a first end and a second end; and    (b) means for simultaneously introducing at least two fluid streams into said first end of said channel; whereby said streams flow in parallel laminar flow within said channel;    (c) said channel having a length sufficient to allow particles flowing in a first one of said streams to diffuse into a second of said streams to form a detection area.    
     
     
         2 . The microfluidic device of  claim 1  wherein said channel contains no internal structures.  
     
     
         3 . The microfluidic device of  claim 1  also comprising said first and second streams flowing in parallel laminar flow therein.  
     
     
         4 . The microfluidic device of  claim 3  wherein said first stream contains particles larger than said particles which diffuse into said second stream, which larger particles remain substantially in said first stream in said channel throughout the length of said channel.  
     
     
         5 . The microfluidic device of  claim 1  also comprising means for detecting said diffused particles in said second stream cooperatively connected with said channel.  
     
     
         6 . A method for transporting particles across a fluid interface comprising: 
 (a) forming a fluid interface between two or more streams flowing within a microfluidic channel by: 
 (i) simultaneously flowing said streams into a laminar flow channel; and  
 (ii) allowing said streams to flow in side-by-side laminar flow within said channel; and  
   (b) allowing particles in a first of said streams to diffuse into a second of said streams.    
     
     
         7 . The method of  claim 6  wherein said streams are of equal volume.  
     
     
         8 . The method of  claim 6  wherein said streams are of equal flow rate.  
     
     
         9 . The method of  claim 6  comprising forming a fluid barrier between said streams.  
     
     
         10 . The method of  claim 9  wherein said fluid barrier is formed by flowing a greater volume of one stream than the other stream into said channel.  
     
     
         11 . The method of  claim 9  wherein the fluid barrier is formed by allowing a lesser volume of one stream that the other to exit said channel.  
     
     
         12 . The method of  claim 6  wherein said streams comprise a particle-containing stream and a particle-receiving stream, and particles contained in the particle-containing stream are allowed to diffuse into the particle-receiving stream.  
     
     
         13 . The method of  claim 6  wherein diffused particles are detected in said second stream.