Electrically conductive ink for solvent-cast 3D printing

1. An ink for solvent-cast 3D printing, the ink comprising:

a solution or a gel of a polymer in a volatile solvent, and

carbon nanotubes dispersed in the solution or gel,

wherein the carbon nanotubes are present in a carbon nanotubes:polymer weight ratio between about 20:80 and about 40:60,

wherein the polymer and carbon nanotubes total concentration is between about 20 and about 35 wt %, based on the total weight of the ink, and

wherein the volatile solvent is a solvent that evaporates at room temperature.

2. The ink of claim 1 , wherein the polymer and carbon nanotubes total concentration is between about 25 and about 30 wt %, based on the total weight of the ink.

3. The ink of claim 1 , wherein the polymer is poly(lactic acid), polystyrene, poly(methyl acrylate), poly(methyl methacrylate), poly(n-butyl acrylate), poly(2-hydroxyethyl methacrylate), poly(glycidyl methacrylate), poly(acrylic acid), poly(N-N-dimethylacrylamide), poly(1-vinyl anthracene), poly(2-vinyl pyridine), poly(4-vinyl pyridine), poly(N-vinyl carbazole), poly(N-vinyl carbazole), poly(N-vinyl imidazole), poly(vinyl benzyl chloride), poly(4-vinyl benzoic acid), poly(vinyl acetate), polycaprolactone, poly(11-[4-(4-butylphenylazo)phenoxy]-undecyl methacrylate) (poly(AzoMA)), poly(ferrocenyldimethylsilane), polyisoprene, polybutadiene, polyisobutylene, poly propylene glycol, poly(ethylene glycol), a polysaccharide, or a mixture thereof.

4. The ink of claim 3 , wherein the polysaccharide is chitosan.

5. The ink of claim 1 , wherein the solvent is dichloromethane (DCM), chloroform (CHCl 3 ), tetrahydrofuran (THF), acetone, methanol (MeOH), ethanol (EtOH), or water.

6. The ink of claim 1 , wherein the ink further comprises one or more additive.

7. The ink of claim 1 , wherein the carbon nanotubes are single-wall carbon nanotubes or multiwall carbon nanotubes.

8. The ink of claim 1 , wherein the polymer is poly(lactic acid) and the solvent is dichloromethane, chloroform, tetrahydrofuran, acetone, methanol, or ethanol.

9. The ink of claim 8 , wherein the solvent is dichloromethane.

10. The ink of claim 1 , wherein the polymer is chitosan, the solvent is water, and the solution or gel of the polymer in the volatile solvent is a chitosan hydrogel.

11. The ink of claim 10 , wherein the ink further comprises one or more weak organic acid.

12. The ink of claim 11 , wherein the ink comprises 70 vol % acetic acid alone or together with 10 vol % lactic acid and 3 wt % citric acid, the vol % being based on the total volume of the water and acids and the wt % being based on the total weight of the water and acids.

13. A method of manufacturing the solvent-cast 3D printing ink of claim 1 , the method comprising the steps of:

a) providing a solution or a gel of a polymer in a solvent,

b) providing carbon nanotubes in a carbon nanotubes:polymer weight ratio of between about 20:80 and about 40:60,

c) dispersing the carbon nanotubes in the solution or gel of the polymer by ball milling, thereby producing the ink, and

d) avoid drying the ink, thus keeping the solvent in the ink, until the ink is used for solvent-cast 3D printing.

14. The method of claim 13 , wherein the concentration of the polymer in the solution or gel of step a) is between about 2 wt % and about 15 wt %, based on the total weight of the solution or gel.

15. The method of claim 13 , wherein the ball milling in step c) is carried out for 10 to 30 minutes.

16. The method of claim 13 , further comprising, before or after step d), the step of adding solvent, or removing part of the solvent so that the polymer and carbon nanotubes total concentration in the ink is between about 20 and about 35 wt %, based on the total weight of the ink.

17. The method of claim 13 , further comprising the step of adding one or more additives to the solvent, to the solution or gel of the polymer, or to the ink.

18. The method of claim 13 , further comprising the step of packaging the ink in a 3D printer ink cartridge.

19. A method of using the solvent-cast 3D printing ink of claim 1 for manufacturing a solvent-cast 3D printed material, the method comprising the steps of:

a) providing the solvent-cast 3D printing ink claim 1 ;

b) using a 3D printer, extruding the ink through a needle into a controlled pattern; and

c) allowing solvent evaporation, thereby providing the solvent-cast 3D printed material.