Microfluidic device for storage and well-defined arrangement of droplets

Abstract

The present invention relates to systems and methods for the arrangement of droplets in pre-determined locations. Many applications require the collection of time-resolved data. Examples include the screening of cells based on their growth characteristics or the observation of enzymatic reactions. The present invention provides a tool and related techniques which addresses this need, and which can be used in many other situations. The invention provides, in one aspect, a tool that allows for stable storage and indexing of individual droplets. The invention can interface not only with microfluidic/microscale equipment, but with macroscopic equipment to allow for the easy injection of liquids and extraction of sample droplets, etc.

What is claimed is: 
     
         1 - 49 . (canceled) 
     
     
         50 . A method of arranging droplets comprising:
 applying an essentially constant pressure gradient along a channel such that a first droplet is urged through a first constriction into a first pot and then urged through a second constriction from the first pot into a second pot.   
     
     
         51 . The method of  claim 50 , further comprising:
 continuing to apply the essentially constant pressure gradient such that a second droplet is urged through the first constriction into the first pot wherein the first droplet is contained within the second pot and the second droplet is contained within the first pot simultaneously.   
     
     
         52 . A method of arranging droplets comprising:
 applying a pressure differential along a channel comprising a series of pots each containing at least one droplet, said pots connected via a series of constrictions arranged such that each pot is in direct fluid communication with no more than two other pots and each pot is connected to exactly two constrictions, and   ejecting the droplets from an exit of the channel in the order in which they were placed in the pots.   
     
     
         53 . The method of  claim 52 , further comprising:
 injecting a fluid after each droplet exits the channel in order to maintain consistent spacing between the droplets that exit the channel.   
     
     
         54 . The method of  claim 53 , further comprising:
 injecting the droplets into a microtiter plate.   
     
     
         55 - 64 . (canceled) 
     
     
         65 . A method of arranging cells at predetermined positions in an array comprising:
 urging a first cell through a first constriction in a channel into a first pot.   
     
     
         66 . The method of  claim 65 , further comprising:
 applying a pressure differential along the channel such that the first cell is urged through a second constriction into a second pot that is downstream of the first pot.   
     
     
         67 . The method of  claim 66 , further comprising:
 applying a pressure differential along the channel such that a second cell is urged through the first constriction into the first pot wherein   upon removal of the applied pressure differential, the first cell is contained within the second pot and the second cell is contained within the first pot simultaneously.   
     
     
         68 . The method of  claim 66 , further comprising:
 transferring the contents of the first pot into a well of a second device through a hole in fluid communication with the first pot.   
     
     
         69 . The method of  claim 65 , wherein the cell remains in a field of view and focal plane of an imaging device while the cell is confined in the pot. 
     
     
         70 . The method of  claim 65 , further comprising:
 urging a plurality of cells toward the channel, wherein:
 the channel comprises a plurality of pots, and 
 at least about 1% of the cells are immobilized within the pots. 
   
     
     
         71 . The method of  claim 70 , wherein the cells are loaded into pots at a rate of at least about 10 cells per second. 
     
     
         72 . The method of  claim 68 , wherein the second device comprises a microtiter plate. 
     
     
         73 . The method of  claim 65 , further comprising:
 measuring a property of the first cell in the first pot using a microarray scanner.   
     
     
         74 . The method of  claim 73 , wherein the property comprises fluorescence. 
     
     
         75 . The method of  claim 74 , further comprising:
 exciting fluorescence in the sample with a laser.   
     
     
         76 . The method of  claim 75 , wherein the excitation is part of a digital PCR process. 
     
     
         77 . The method of  claim 65 , further comprising:
 measuring a property of the first cell in the first pot.   
     
     
         78 . The method of  claim 50 , further comprising transferring the contents of the first pot, through a hole in fluid communication with the first pot, and into a well of a second device. 
     
     
         79 . The method of  claim 50 , wherein the first droplet remains in a field of view and focal plane of an imaging device while the droplet is confined in the second pot.