Roll-to-Roll Transfer Printing of Reduced Graphene Oxide Thin Film

A novel thin film transfer mechanism has been studied and developed to transfer chemically reduced graphene oxide (r-GO) thin film using a roll-to-roll printing system. We discover that shear stress generated on the silicon rubber stamp surface facilitates delamination of the deposited r-GO thin film efficiently.A roll-to-roll apparatus is assembled to demonstrate the shear-induced transfer printing in a large scale printing system. Shear stress is applied on the stamp surface by rotating the stamp side roller faster than the substrate side roller.The hydrophobic surface is changed to hydrophilic by polydopamine modification for 15 minutes at 60˚C in order for r-GO thin film to be directly deposited on the rubber stamp.Roll-to-roll printing parameters such as evaporation time during deposition of r-GO, vertical deformation of stamp, RPM, and RPM ratio between two rollers are investigated and adjusted for successful transfer of r-GO.With the adjusted roll-to-roll printing parameters, r-GO thin film has been transferred successfully to glass and PET substrates at a printing rate of 5mm/min. The shear stress required to transfer r-GO thin film in our experiment condition with glass substrate is estimated to be 325.43 kPa by experimental data and computation with ANSYS.A flexible transparent capacitive touch sensor is fabricated with printed r-GO thin film after the sheet resistance is significantly improved by thermal annealing process.Both the shear-induced roll-to-roll printing method and the stamp modification process are expected to contribute to large scale manufacturing systems for flexible printed electronics.