3D printing using phase changing matertials as support

1. A cartridge for three-dimensionally printing, the cartridge comprising:

a housing configured for insertion in a three-dimensional printing device;

a recess in the housing;

a first material within the recess, the first material comprising a Herschel-Bulkley material, wherein the Herschel-Bulkley material is a soft granular gel made from polymeric packed micro-particles having a yield stress less than 100 Pascals; and

an opening in the housing configured for an injector to pass through the housing into the recess and displace the first material with a second material,

wherein the first material is permeable by focused energy applied to a region of the first material using a focused energy source.

2. The cartridge of claim 1 , wherein the polymeric packed micro-particles are between 0.1 and 100 micrometers in diameter.

3. The cartridge of claim 1 , wherein the polymeric packed micro-particles are approximately 5 micrometers in diameter.

4. The cartridge of claim 1 , wherein the polymeric packed micro-particles are at a concentration by weight in the soft granular gel of less than 2%.

5. The cartridge of claim 4 , wherein the polymeric packed micro-particles are at a concentration by weight in the soft granular gel of between 0.5% and 1%.

6. The cartridge of claim 1 , wherein the polymeric packed micro-particles are at a concentration by mass in the soft granular gel of between 0.2% and 0.7%.

7. The cartridge of claim 1 , wherein the first material comprises a hydrogel.

8. The cartridge of claim 7 , wherein the hydrogel comprises a carbomer polymer.

9. The cartridge of claim 7 , wherein the hydrogel comprises crosslinked polymers of acrylic acid.

10. The cartridge of claim 7 , wherein the hydrogel comprises a polyelectrolytic microgel.

11. The cartridge of claim 1 , wherein the first material comprises a silicone elastomer dispersion.

12. The cartridge of claim 11 , wherein the silicone elastomer dispersion comprises a silicone elastomer dispersed in PDMS.

13. The cartridge of claim 1 , wherein the yield stress of the first material is between 1 and 100 Pascals.

14. The cartridge of claim 13 , wherein the yield stress of the first material is between 10 and 100 Pascals.

15. The cartridge of claim 1 , wherein a shear stress of the first material is independent of shear rate at a shear rate of 10 −3 s −1 .

16. The cartridge of claim 1 , wherein the shear stress of the first material at a shear rate of 10 −3 s −1 is dependent only on an elastic component of the first material.

17. The cartridge of claim 1 , wherein the yield stress of the first material is below a hydrostatic pressure of the first material.

18. The cartridge of claim 1 , wherein the first material has a thixotropic time between 0.25 second and 2.5 second.

19. The cartridge of claim 1 , wherein the first material has a thixotropic index between 4 and 7.

20. The cartridge of claim 18 , wherein the first material has a thixotropic time between 0.25 seconds and 1.5 seconds.

21. The cartridge of claim 1 , wherein the first material and the second material are miscible.

22. An apparatus for creating a three-dimensional structure, the apparatus comprising:

a container to hold a first material;

a focused energy source configured to cause a phase change in a region of the first material by applying focused energy to the region; and

an injector configured to displace first material in the region with a second material,

wherein the first material is a Herschel-Bulkley material, the Herschel-Bulkley material comprising a soft granular gel made from polymeric packed micro-particles having a yield stress less than 100 Pascals.

23. The apparatus of claim 22 , wherein the focused energy source is configured to cause a reverse phase change in the region of the first material.

24. The apparatus of claim 22 , wherein the second material comprises extracellular matrix materials precursor solution.

25. The apparatus of claim 22 , wherein the second material comprises one or more cells.

26. The apparatus of claim 22 , further comprising:

a platform configured to cause relative displacement between the first material and the injector.

27. The apparatus of claim 26 , wherein the relatively displacement between the first material and the injector comprises relative rotation between the first material and the injector.

28. The apparatus of claim 27 , wherein the relative rotation between the first material and the injector comprises rotation about an axis of the first material.

29. The apparatus of claim 26 , wherein the platform is configured to cause the relative displacement between the first material and the injector at a displacement rate faster than a characteristic breakup time of a jet of the second material.

30. The apparatus of claim 22 , further comprising:

an actuator configured to cause relative displacement between a focus point of the focused energy source and the first material.

31. The apparatus of claim 30 , wherein the platform and/or the actuator are configured such that motion of the platform is synchronized with motion of the actuator.

32. The apparatus of claim 22 , wherein the first material is releasable from containment.

33. The apparatus of claim 22 , further comprising:

a second injector to wash away the first material to release the second material from the first material.

34. The apparatus of claim 33 , wherein the second injector is configured to inject one or more salts and/or organic solvents into the first material.

35. The apparatus of claim 22 , wherein the apparatus is configured to operate the injector to displace the first material with the second material for an indefinite time.

36. The apparatus of claim 22 , wherein the apparatus is configured to operate the injector to continuously displace the first material with the second material for a time greater than one day.