DROPLET CREATION TECHNIQUES

• US 20120222748A1
• Filed: 10/26/2010
• Published: 09/06/2012
• Est. Priority Date: 10/27/2009
• Status: Active Grant

• Current Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Original Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Inventors: Weitz, David A., Abate, Adam R.
• Granted Patent: US 9,056,289 B2
• Time in Patent Office: Days
• US Class Current: 137/1
• CPC Class Codes: B01F 23/41 Emulsifying
• CPC Class Codes: B01F 33/3011 using a sheathing stream of a fluid surrounding a central stream of a different fluid, e.g. for reducing the cross-section of the central stream or to produce droplets from the central stream
• CPC Class Codes: B01F 33/3021 the components to be mixed being combined in a single independent droplet, e.g. these droplets being divided by a non-miscible fluid or consisting of independent droplets
• CPC Class Codes: B01L 2200/0636 Focussing flows, e.g. to laminate flows
• CPC Class Codes: B01L 2200/0652 Sorting or classification of particles or molecules
• CPC Class Codes: B01L 2300/0681 Filter
• CPC Class Codes: B01L 3/0241 Drop counters; Drop formers making arrays for combinatorial libraries B01J19/0046; automation of dispensing for analysis G01N35/10
• CPC Class Codes: B01L 3/502761 specially adapted for handling suspended solids or molecules independently from the bulk fluid flow, e.g. for trapping or sorting beads, for physically stretching molecules investigating characteristics of particles G01N15/00
• CPC Class Codes: B01L 3/502784 specially adapted for droplet or plug flow, e.g. digital microfluidics automatic analysis using a stream of discrete samples in a tube system G01N35/08
• CPC Class Codes: Y10T 137/0318 Processes
• CPC Class Codes: Y10T 137/8593 Systems

Abstract

The present invention is generally related to systems and methods for producing droplets. The droplets may contain varying species, e.g., for use as a library. In some cases, at least one droplet is used to create a plurality of droplets, using techniques such as flow-focusing techniques. In one set of embodiments, a plurality of droplets, containing varying species, can be divided to form a collection of droplets containing the various species therein. A collection of droplets, according to certain embodiments, may contain various subpopulations of droplets that all contain the same species therein. Such a collection of droplets may be used as a library in some cases, or may be used for other purposes.

Claims

1. A method for forming a plurality of droplets, comprising:

providing at least one droplet comprising a first fluid substantially surrounded by a second fluid; and

passing the at least one droplet through a microfluidic channel to form a plurality of divided droplets.

2. The method of claim 1, wherein the first fluid and the second fluid are substantially immiscible.

3. The method of claim 1, wherein the plurality of divided droplets are substantially surrounded by the second fluid.

4. The method of claim 1, comprising providing a plurality of droplets, each substantially surrounded by the second fluid, and passing at least some of the droplets through the microfluidic channel such that each of the droplets passing through the microfluidic channel are divided to form two or more of the divided droplets.

5. The method of claim 1, comprising providing a plurality of droplets, each substantially surrounded by the second fluid, and passing at least some of the droplets through the microfluidic channel such that each of the droplets passing through the microfluidic channel are divided to form substantially the same number of divided droplets.

6. The method of claim 4, wherein, for each of the droplets passing through the microfluidic channel, the two or more divided droplets that are formed from each of the droplets have a distribution of diameters such that no more than about 5% of the divided droplets have a diameter greater than about 10% of the average diameter of all of the divided droplets that are formed.

7. The method of claim 5, wherein the plurality of divided droplets has a distribution of diameters such that no more than about 5% of the droplets have a diameter greater than about 10% of the average diameter of the droplets.

8. The method of claim 5, wherein the plurality of droplets contains therein at least four distinguishable species, such that no more than about 5% of the droplets contains two or more of the at least four distinguishable species therein.

9. The method of claim 8, wherein the at least four distinguishable species comprises at least four distinguishable nucleic acids.

10. The method of claim 8, wherein the at least four distinguishable species comprises at least four distinguishable identification elements.

11. The method of claim 8, wherein the at least four distinguishable species comprises at least four distinguishable proteins.

12. The method of claim 1, wherein the at least one droplet has an average diameter greater than about 500 microns and the plurality of divided droplets has an average diameter of less than about 500 microns.

13. The method of claim 1, wherein at least about 10 divided droplets are formed from the at least one first droplet.

14. The method of claim 1, wherein at least about 50 divided droplets are formed from the at least one first droplet.

15. The method of claim 1, wherein the average diameter of the plurality of second divided droplets is less than about 1000 microns and wherein the droplets are substantially monodisperse.

16. The method of claim 1, comprising providing a first droplet comprising at least one first species and a second droplet comprising at least one second species distinguishable from the first species.

17. The method of claim 16, comprising forming an emulsion comprising a plurality of divided droplets, each divided droplet comprising a portion of the first droplet or the portion of the second droplet, wherein the average diameter of the divided droplets in the emulsion is less than about 1000 microns.

18. An article, comprising:

a fluid containing a plurality of droplets, at least some of which have distinguishable compositions; and

a flow-focusing device able to produce divided droplets using the plurality of droplets contained within the fluid, the produced divided droplets having a distribution of diameters such that no more than about 5% of the droplets have a diameter greater than about 10% of the average diameter of the droplets.

19. The article of claim 18, wherein the fluid contains at least 5 distinguishable droplets.

20. The article of claim 18, wherein at least 10 divided droplets are produced from each droplet.