Dissolving droplet microfluidic particle assembly devices and methods, and particle assemblies obtained therefrom

1. A device for assembling a plurality of particles into particle assemblies, said device comprising:

(a) a microfluidic droplet-generating region;

(b) a first inlet to said droplet-generating region, wherein said first inlet is configured to feed a first fluid containing particles and a solvent for said particles;

(c) a second inlet to said droplet-generating region, wherein said second inlet is configured to feed a second fluid that is not fully miscible with said first fluid;

(d) a droplet outlet from said droplet-generating region, wherein said droplet outlet is configured to withdraw droplets of said first fluid dispersed in said second fluid; and

(e) a droplet-dissolving region configured to receive said droplets from said droplet outlet, wherein said droplet-dissolving region is configured to remove said solvent from said droplets, thereby forming particle assemblies.

2. The device of claim 1 , said device further comprising a third inlet to said droplet-generating region, wherein said third inlet is configured to feed said second fluid.

3. The device of claim 1 , wherein said droplet-generating region contains said first fluid and said second fluid.

4. The device of claim 3 , wherein said droplet-dissolving region contains a third fluid that is different than said first fluid, and wherein said first fluid is partially soluble in said third fluid.

5. The device of claim 4 , wherein said third fluid is different than said second fluid.

6. The device of claim 4 , wherein said third fluid is the same as said second fluid.

7. The device of claim 1 , wherein said droplet-dissolving region is configured with agitation.

8. The device of claim 1 , wherein a temperature-control component is in thermal communication with said device or with a region of said device.

9. A method of assembling a plurality of particles into particle assemblies, said method comprising:

(a) obtaining a first fluid containing particles and a solvent for said particles;

(b) obtaining a second fluid, wherein said first fluid is not fully miscible in said second fluid;

(c) obtaining a third fluid, wherein said first fluid is partially soluble in said third fluid;

(d) introducing said first and second fluids into a microfluidic droplet-generating region, thereby generating an emulsion containing a dispersed phase of droplets of said first fluid in said second fluid;

(e) introducing said emulsion to a droplet-dissolving region containing said third fluid; and

(f) dissolving said solvent from said droplets into said third fluid, thereby forming particle assemblies.

10. The method of claim 9 , wherein said first fluid has a solubility in said second fluid from 0 vol % (completely immiscible) to about 20 vol %.

11. The method of claim 9 , wherein said third fluid is different than said second fluid.

12. The method of claim 9 , wherein said droplet-dissolving region is agitated.

13. The method of claim 9 , wherein the temperature of said first fluid, the temperature of said second fluid, and/or the temperature of said third fluid are controlled with one or more temperature-control components.

14. The method of claim 9 , wherein steps (d), (e), and (f) are continuous.

15. The method of claim 14 , wherein the flow rate of said second fluid is at least ten times the flow rate of said first fluid.

16. The method of claim 9 , said method further comprising adjusting pH of said first fluid, prior to step (d).

17. The method of claim 9 , wherein the assembly dispersity index of said particle assemblies is less than 0.1.

18. The method of claim 9 , wherein in step (f), the number of said particle assemblies equals the number of said droplets.

19. The method of claim 9 , wherein said method does not utilize a substrate for said particle assemblies.

20. The method of claim 9 , wherein said particles include first particles and second particles, wherein said second particles are larger than said first particles, and wherein said particle assemblies are core-shell particle assemblies.

21. An assembly of nanoparticles, wherein said assembly has a volume from 1 μm 3 to 1 mm 3 , a packing fraction from 20% to 100%, and an average relative surface roughness less than 5%, wherein said average relative surface roughness is calculated as a ratio of size of an assembly-surface protrusion to the diameter of said assembly, averaged across the entire surface of said assembly, and wherein said assembly is not disposed on a substrate.

22. The assembly of claim 21 , wherein said packing fraction is at least 90%.

23. The assembly of claim 21 , wherein said average relative surface roughness is less than 1%.

24. The assembly of claim 21 , wherein said assembly is spherical.

25. The assembly of claim 21 , wherein said assembly has an aspect ratio of at least 1.2.

26. The assembly of claim 21 , wherein said assembly is a core-shell assembly.

27. The assembly of claim 21 , wherein said assembly contains a material selected from the group consisting of metals, metal oxides, metal fluorides, metal sulfides, metal phosphides, semiconductors, ceramics, glasses, polymers, and combinations thereof.

28. The assembly of claim 21 , wherein said assembly is free of organic ligands.