Methods and devices for immobilization of single particles in a virtual channel in a hydrodynamic trap

Abstract

Disclosed herein are methods of immobilizing a particle which comprise focusing the flow of a sample fluid containing the particle into a virtual channel which flows towards an unoccupied hydrodynamic trap in a microfluidic channel such that the particle flows into the hydrodynamic trap and becomes immobilized therein. Also disclosed are microfluidic devices which comprise at least one microchannel having at least one hydrodynamic trap, at least one focusing fluid inlet, said focusing fluid inlet is upstream of the hydrodynamic trap such that a focusing fluid introduced therein results in a virtual channel of a sample fluid when present which preferentially flows toward the hydrodynamic trap.

We claim: 
     
         1 . A method of immobilizing a particle which comprises
 focusing the flow of a sample fluid containing the particle into a virtual channel which flows towards an unoccupied hydrodynamic trap in a microfluidic channel such that the particle flows into the hydrodynamic trap and becomes immobilized therein.   
     
     
         2 . The method of  claim 1 , wherein hydrodynamic focusing and a focusing fluid is used for focusing the flow. 
     
     
         3 . The method according to  claim 1 , wherein the center of mass of the particle is located in the virtual channel. 
     
     
         4 . The method according to  claim 1 , wherein the flow stream of the sample fluid towards the unoccupied hydrodynamic trap is greater than the flow stream of the sample fluid which passes by the unoccupied hydrodynamic trap. 
     
     
         5 . The method according to  claim 1 , wherein the hydrodynamic trap is a cavity having a diameter of about 20 μm. 
     
     
         6 . The method according to  claim 1 , wherein the hydrodynamic trap has a micropore. 
     
     
         7 . The method according to  claim 1 , which further comprises flowing a subsequent particle in the focused flow past the immobilized particle. 
     
     
         8 . The method of  claim 7 , wherein the flow path of the subsequent particle is towards a subsequent hydrodynamic trap. 
     
     
         9 . The method of  claim 8 , wherein the subsequent particle becomes immobilized in the subsequent hydrodynamic trap. 
     
     
         10 . The method according to  claim 1 , wherein the subsequent particle is the same or different from the particle. 
     
     
         11 . The method according to  claim 1 , wherein the subsequent hydrodynamic trap is the same or different from the hydrodynamic trap. 
     
     
         12 . The method according to  claim 1 , which further comprises subjecting the focused flow to secondary fluid focusing. 
     
     
         13 . The method of  claim 12 , wherein the secondary fluid focusing is conducted with a second focusing fluid which is the same or different from the focusing fluid. 
     
     
         14 . The method of  claim 12 , wherein the secondary fluid focusing changes the dimensions of the virtual channel. 
     
     
         15 . The method according to  claim 1 , which further comprises detecting and selecting the particle prior to focusing the sample fluid. 
     
     
         16 . The method according to  claim 1 , wherein the hydrodynamic trap has a trapping agent which may be the same or different. 
     
     
         17 . A method of making an array of a plurality of particles each individually immobilized in a plurality of hydrodynamic traps which comprises immobilizing each particle according to  claim 1 .