Particle focusing systems and methods

Abstract

A particle focusing system includes an inlet; an inertial focusing microchannel disposed in a substrate and connected to the inlet; and a pressure/flow source configured to drive a particle-containing fluid through the inertial focusing microchannel, where the inertial focusing microchannel includes a side wall having an irregular surface. The side wall includes a first irregularity protruding from a baseline surface away from a longitudinal axis of the inertial focusing microchannel. Alternatively or additionally, the first irregularity and the baseline surface form an angle more than or equal to 135 degrees. The inertial focusing microchannel may have a substantially rectangular cross-section having a height and a width, and a ratio of height to width is approximately 5:4 to 4:1. The system may also include a downstream expanding region having a side wall, where the side wall has a stepped surface.

1 . A particle focusing system, comprising:
 an inlet;   an inertial focusing microchannel disposed in a substrate and connected to the inlet; and   a pressure/flow source configured to drive a particle-containing fluid through the inertial focusing microchannel, wherein the inertial focusing microchannel comprises a side wall having an irregular surface.   
     
     
         2 . A particle analyzing system, comprising:
 an inlet;   an inertial focusing microchannel disposed in a substrate and connected to the inlet;   a pressure/flow source configured to drive a particle-containing fluid through the inertial focusing microchannel; and   a particle analyzer disposed adjacent a distal end of the inertial focusing microchannel and configured to analyze particles in the distal end of the inertial focusing microchannel, wherein the inertial focusing microchannel comprises a side wall having an irregular surface.   
     
     
         3 . The system of  claim 1 , wherein the side wall comprises a first irregularity protruding from a baseline surface away from a longitudinal axis of the inertial focusing microchannel. 
     
     
         4 . The system of  claim 3 , wherein the first irregularity and the baseline surface form an angle more than or equal to 135 degrees. 
     
     
         5 . The system of  claim 3 , wherein the side wall further comprises a second irregularity protruding from the baseline surface away from a longitudinal axis of the inertial focusing microchannel. 
     
     
         6 . The system of  claim 5 , wherein the first irregularity and the second irregularity have different shapes. 
     
     
         7 . The system of  claim 6 , wherein each irregularity has a shape selected from the group consisting of trapezoidal, triangular, rounded, and rectangular. 
     
     
         8 . The system of  claim 5 , wherein the inertial focusing microchannel further comprises a first section having first irregularities protruding from the baseline surface away from a longitudinal axis of the inertial focusing microchannel and a second section having second irregularities protruding from the baseline surface away from a longitudinal axis of the inertial focusing microchannel, and wherein the first irregularities are axially shorter than the second irregularities. 
     
     
         9 . The system of  claim 1 , wherein the side wall comprises a plurality of irregularities protruding from a baseline surface away from a longitudinal axis of the inertial focusing microchannel. 
     
     
         10 . The system of  claim 9 , wherein at least two irregularities are axially separated from respective next irregularities by different axial distances. 
     
     
         11 . The system of  claim 9 , wherein at least two of the irregularities have different shapes. 
     
     
         12 . The system of  claim 1 , further comprising an additional inlet. 
     
     
         13 . The system of  claim 1 , wherein the inertial focusing microchannel has a substantially rectangular cross-section having a height and a width, and a ratio of height to width is approximately 5:4 to 4:1. 
     
     
         14 . The system of  claim 1 , further comprising a downstream expanding region having a side wall, wherein the side wall has a stepped surface. 
     
     
         15 . The system of  claim 1 , further comprising a downstream expanding region having a side wall, wherein the side wall has a curved surface. 
     
     
         16 . A method of focusing particles in a fluid into a substantially axially aligned and ordered particle stream, comprising:
 flowing an unprocessed fluid having particles suspended therein through a particle focusing system, wherein the particle focusing system comprises:
 a first inlet; 
 an inertial focusing microchannel disposed in a substrate and connected to the inlet; and 
 a pressure/flow source configured to drive a particle-containing fluid through the inertial focusing microchannel, wherein the inertial focusing microchannel comprises a side wall having an irregular surface. 
   
     
     
         17 . The method of  claim 16 , wherein the inertial focusing microchannel has width W, and the fluid has density ρ, maximum velocity U m , and viscosity μ, and wherein the unprocessed fluid is flowed through the particle focusing system at a flow rate such that channel Reynolds number, R c =ρU m W/μ, is larger than 1. 
     
     
         18 . The method of  claim 16 , wherein flowing unprocessed fluid through the particle focusing system comprises flowing the unprocessed fluid over the irregular surface of the microchannel side wall to increase a rate of focusing. 
     
     
         19 . The method of  claim 16 , wherein the particle focusing system further comprises a second inlet and wherein the unprocessed fluid having particles suspended therein is flowed through the first inlet, the method further comprising flowing a particle free fluid through the second inlet simultaneously with flowing the unprocessed fluid through the first inlet. 
     
     
         20 . The method of  claim 19 , wherein the side wall comprises a first irregularity protruding from a baseline surface away from a longitudinal axis of the inertial focusing microchannel, and wherein flowing the unprocessed fluid over the irregularity increases an inter-particle spacing in the particle stream. 
     
     
         21 . The method of  claim 19 , wherein the inertial focusing microchannel further comprises a first section having first irregularities protruding from the baseline surface away from a longitudinal axis of the inertial focusing microchannel and a second section having second irregularities protruding from the baseline surface away from a longitudinal axis of the inertial focusing microchannel, wherein the first irregularities are axially shorter than the second irregularities, and wherein flowing unprocessed fluid through the particle focusing system comprises flowing the unprocessed fluid through the first section to increase a rate of focusing and flowing the unprocessed fluid through the second section to tune a particle frequency of the particle stream.