Graphene ink holds promise for low cost, foldable electronics

Led by Professor Mark Hersam, the team has developed a graphene based ink that is highly conductive and tolerant to bending, and has used it to inkjet print graphene patterns that could be used for extremely detailed, conductive electrodes. The resulting patterns are said to be 250 times more conductive than previous attempts to print graphene based electronic patterns, and could be a step toward bendable tablets and electronic newspapers that fit neatly inside your back pocket. "Graphene has a unique combination of properties that is ideal for next generation electronics, including high electrical conductivity, mechanical flexibility and chemical stability," said Prof Hersam. "By formulating an inkjet printable ink based on graphene, we now have an inexpensive and scalable path for exploiting these properties in real world technologies." While inkjet printing with graphene is extremely promising, it has so far remained a challenge for researchers because it is difficult to harvest a sufficient amount of graphene without compromising its electronic properties. The Northwestern team claims to have overcome this and has found a way to mass produce graphene while maintaining its conductivity, using a process that can be carried out at room temperature using ethanol and ethyl cellulose to exfoliate graphite. This relatively clean process is said to minimise residues and result in a powder with a high concentration of nanometre sized graphene flakes. This is then mixed into a solvent to create the ink. The researchers demonstrated printing the ink in multiple layers, each 14nm thick, to create precise patterns. In testing, the ink's conductivity remained virtually unchanged, even when bent to a great degree, suggesting that graphene inks could be used to create foldable electronic devices in the future.