High-resolution patterning of graphene by screen and gravure printing for highly flexible printed electronics
Graphene ink compositions as can be utilized with gravure and screen printing processes, to provide flexible electronic components with high-resolution printed graphene circuitry.
1. A method of preparing a graphene ink composition, said method comprising:
exfoliating graphene from a graphene source material with a medium comprising an organic solvent and a cellulosic polymer at least partially soluble in said organic solvent;
contacting at least a portion of said exfoliated graphene medium with an aqueous medium to concentrate exfoliated graphene in a composition comprising graphene and a said cellulosic polymer;
contacting said graphene-cellulosic composition with a hydrophobic fluid comprising an ink solvent and a dispersion solvent; and
removing said dispersion solvent from said hydrophobic fluid, to provide a graphene ink composition comprising said ink solvent, said cellulosic polymer, a solids concentration and viscosity.
2. The method of claim 1 wherein said ink solvent is selected from terpenes, terpene alcohols and combinations thereof.
3. The method of claim 2 wherein said hydrophobic fluid component comprises a terpineol and ethanol.
4. The method of claim 1 wherein said graphene source material is graphite.
5. The method of claim 1 wherein said exfoliation comprises shear mixing said graphene source material and said organic solvent.
6. The method of claim 1 wherein said ink composition has a solids concentration of 5 to 10% w/v, and a viscosity of 0.1 to 1.0 Pa·s.
7. The method of claim 6 comprising gravure printing of said ink composition on a substrate.
8. The method of claim 7 wherein said ink composition has a graphene content of 30 to 40 wt %.
9. The method of claim 8 wherein said graphene ink composition is photoannealed to decompose said cellulosic polymer.
10. The method of claim 1 wherein said ink composition has a solids concentration of 10% to 20% w/v, and a viscosity of 5 to 100 Pa·s.
11. The method of claim 10 comprising screen printing of said ink composition on a substrate.
12. The method of claim 11 wherein said ink composition has a graphene content of at least 50 wt %.
13. The method of claim 12 wherein said graphene ink composition is photoannealed to decompose said cellulosic polymer.
14. The method of claim 1 wherein said organic solvent is selected from C 2 -C 5 alcohols, esters, amides, ethers and ketones and combinations thereof.
15. The method of claim 14 wherein said organic solvent is selected from ethanol and dimethylformamide.