Mixed mode microfluidic systems

Abstract

Methods and systems that employ hybrid fluid flow profiles for optimized movement of materials through channel networks. These systems employ hybrid pressure-based and electrokinetic based flow systems for moving materials through interconnected channel networks while maintaining interconnection among the various channel segments. In particular, the invention is generally directed to channel networks where flow in a first channel segment is driven by pressure flow with its consequent parabolic flow profile, while flow in an interconnected channel segment is dominated by electrokinetic flow with its consequent plug flow profile. The invention also provides channel networks wherein fluid flow in channel segments is driven by both pressure and electric field and the multiple species contained in a fluid plug are separated by altering the applied pressure and electric fields in the various channel segments of the channel networks.

1 . A method of transporting material, comprising: 
 providing a first channel segment, a second channel segment, and a third channel segment, each channel segment having first and second ends, wherein the second end of the first channel segment, the first end of the second channel segment, and the first end of the third channel segment are fluidly coupled at a first fluid junction;    applying a pressure differential between the first end of the first channel segment and the second end of the third channel segment to produce a first flow profile in the first channel segment, the first flow profile being dominated by non-electrokinetically driven pressure flow; and    applying a voltage differential between the second end of the second channel segment and the second end of the third channel segment to produce a second flow profile in the second channel segment, the second flow profile being dominated by electrokinetic flow;    thereby transporting material through the first channel segment and into the second channel segment.    
     
     
         2 . The method of  claim 1 , wherein the second flow profile is substantially devoid of non-electrokinetically driven flow.  
     
     
         3 . The method of  claim 1 , wherein the second flow profile comprises a slower flow rate than a flow rate in the first flow profile.  
     
     
         4 . The method of  claim 3 , wherein the flow rate of the second flow profile is less than one half the flow rate of the first flow profile.  
     
     
         5 . A system for transporting material, comprising: 
 a first channel segment having first and second ends, and a second channel segment having first and second ends, the second end of the first channel segment being fluidly coupled to the first end of the second channel segment at a first fluid junction;    a flow access channel fluidly coupled to the first fluid junction; and    a flow control system operably coupled to the flow access channel and the first and second channel segments, the flow control system being configured to provide a first flow profile through the first channel segment and a second flow profile through the second channel segment, the first flow profile being dominated by non-electrokinetic pressure flow, and the second flow profile being dominated by electrokinetic flow, the first and second flow profiles combining to yield a flow of material through the first channel segment into the second channel segment with substantially no flow of material into or out of the flow access channel.    
     
     
         6 . The system of  claim 5 , wherein the first and second channel segments and flow access channel are disposed in a body structure of a microfluidic device.  
     
     
         7 . The system of  claim 5 , wherein the flow of material through the first channel segment into the second channel is constant.  
     
     
         8 . The system of  claim 6 , wherein the flow control system comprises at least a first pressure source and at least a first voltage source.