A novel method to improve the line resolution of stretchable graphene-based line by embedded uniform droplet printing

Solution-phase printing of nanomaterials is a low-cost and effective way to build functional devices. While a multitude of industries have witnessed steady progress in it, the low line resolution remains a challenge for inkjet printing, since the droplet spreading on a substrate inevitably widens the printing tracks. In the present work, a novel embedded printing method based on a liquid viscous film to produce high-resolution lines without a small nozzle(<20 μm in diameter) or modified substrates was demonstrated. The influences of pre-cured time, substrate velocity and solvent ratio on the diameter of a single droplet and the continuity of multiple droplets were explored. A cylindrical reduced graphene oxide (rGO) line with a diameter of 10 μm had been deposited on the surface of the viscous liquid substrate and slowly wrapped into polydimethylsiloxane (PDMS) thin film by using a nozzle of 110 μm in diameter after optimizing the experimental parameters. The rGO lines encapsulated into PDMS could be stretched to 180% of its original length, during which no shedding or breaking occurred. This work presents a facile way to improve the line resolution of flexible/stretchable graphene-based lines, which probably contribute to further application of inkjet printing technology in the field of flexible and stretchable devices.