Embolization

1. A method of making particles, the method comprising:

combining a plurality of streams of fluid to form drops; and

forming particles from the drops, wherein the particles contain pores and have an arithmetic mean diameter of from about ten microns to about 3,000 microns.

2. The method of claim 1 , wherein the plurality of streams of fluid comprises a first stream including a first material and a second stream including a second material.

3. The method of claim 2 , further comprising flowing the first material through a first orifice defined by a nozzle to form the first stream.

4. The method of claim 3 , wherein the first orifice has a diameter of from about 50 microns to about 1,000 microns.

5. The method of claim 3 , wherein the first orifice has a diameter of from about 50 microns to about 300 microns.

6. The method of claim 3 , further comprising flowing the second material through a second orifice defined by the nozzle to form the second stream.

7. The method of claim 6 , wherein the second orifice has a first diameter of from about 50 microns to about 1,000 microns.

8. The method of claim 6 , wherein the second orifice has a first diameter of from about 100 microns to about 600 microns.

9. The method of claim 6 , wherein the second orifice has a second diameter of from about 50 microns to about 1,000 microns.

10. The method of claim 6 , wherein the second orifice has a second diameter of from about 100 microns to about 600 microns.

11. The method of claim 6 , wherein the first orifice has a diameter and the second orifice has a diameter, and a difference between the diameter of the second orifice and the diameter of the first orifice is at least about 50 microns.

12. The method of claim 6 , wherein the first orifice is disposed within the second orifice.

13. The method of claim 12 , wherein the first orifice and the second orifice are concentric.

14. The method of claim 13 , wherein the first orifice is disposed at a vertical distance of about one millimeter from the second orifice.

15. The method of claim 6 , wherein the first material flows through the first orifice at a rate of from about two milliliters per minute to about ten milliliters per minute.

16. The method of claim 15 , wherein the second material flows through the second orifice at a rate of from about two milliliters per minute to about 20 milliliters per minute.

17. The method of claim 2 , wherein the first material comprises a polymer.

18. The method of claim 2 , wherein the second material comprises a gelling precursor.

19. The method of claim 18 , wherein forming the particles includes converting the gelling precursor from a solution into a gel, and the method further comprises removing at least some of the gel from the particles.

20. The method of claim 2 , wherein the first material and the second material are immiscible.

21. The method of claim 2 , wherein the first stream and the second stream are concentric.

22. The method of claim 2 , wherein the first material forms an interior region of the drops and the second material forms a surface region of the drops.

23. The method of claim 2 , wherein a viscosity of the first material is greater than a viscosity of the second material.

24. The method of claim 2 , wherein a viscosity of the second material is greater than a viscosity of the first material.

25. The method of claim 1 , wherein the particles have a first density of pores in an interior region and a second density of pores at a surface region, the first density being different from the second density.

26. The method of claim 25 , wherein the first density is greater than the second density.

27. The method of claim 1 , wherein the particles have a first average pore size in an interior region and a second average pore size at a surface region, the first average pore size being different from the second average pore size.

28. The method of claim 27 , wherein the first average pore size is greater than the second average pore size.

29. The method of claim 1 , wherein the plurality of streams is two streams.

30. The method of claim 1 , wherein the plurality of streams comprises at least three streams.

31. The method of claim 1 , wherein forming the drops includes exposing the plurality of streams to a periodic disturbance.

32. The method of claim 31 , wherein the periodic disturbance is provided by vibrating the plurality of streams.

33. The method of claim 1 , wherein forming the drops includes establishing an electrostatic potential between the plurality of streams and a vessel configured to receive the drops.

34. A method of making particles, the method comprising:

combining a first stream including a polymer and a second stream including a gelling precursor to form drops; and

forming particles from the drops, wherein the particles contain pores.

35. The method of claim 34 , wherein the particles have an arithmetic mean diameter of from about ten microns to about 3,000 microns.

36. A method of making particles, the method comprising:

forming a plurality of streams of fluid from a plurality of orifices;

combining the plurality of streams of fluid to form drops; and

forming particles from the drops,

wherein the particles contain pores and a first orifice of the plurality of orifices has a diameter of from about 50 microns to about 1000 microns, and a second orifice of the plurality of orifices has a first diameter of from about 50 microns to about 1000 microns and a second diameter of from about 50 microns to about 1000 microns, wherein the second diameter of the second orifice is different from the diameter of the first orifice.

37. The method of claim 36 , wherein the first orifice has a diameter of from about 50 microns to about 300 microns.

38. The method of claim 36 , wherein the second orifice has a first diameter of from about 100 microns to about 600 microns.

39. The method of claim 38 , wherein the second orifice has a second diameter of from about 100 microns to about 600 microns.

40. The method of claim 36 , wherein a difference between the second diameter of the second orifice and the diameter of the first orifice is at least about 100 microns.

41. The method of claim 36 , wherein the first orifice and the second orifice are concentric.