Laser-induced transfer of graphene on flexible substrates for touch sensor application

Abstract

In the current work we will present the transfer of graphene pixels and arrays. The process we used to accomplish the transfer was the Laser Induced Transfer technique. We will exhibit the advantages of the certain technique, the resolution of the transferred pixels and the characterization of the samples. Also, we will demonstrate the transfer of graphene arrays on both flexible polymeric and rigid substrates. The transfer of the graphene pixels was accomplished for resolution from 40 μm to 15 μm, whereas the digital manipulation of the transfer enables the deposition of arrays with dimension up to 1 mm2. Furthermore, in this work we will present the fabrication of a flexible capacitance touch sensor. The device is composed by LIFT transfer bottom electrodes and top electrodes and between them we deposit a insulating layer with the assistance of a spin-coater. For bottom electrodes we used silver nanoparticles ink, which was LIFT transferred and laser sintered in order to be conductive and form two pads with a line to connect them. The top electrode is a transferred graphene array with dimension at 1 mm2 and the insulating layer we used is an in-house fabricated PDMS, which was deposited on the half of the bottom electrodes. The quality and quantity of graphene layers were measured and characterized with Scanning Electron Microscopy and micro-Raman spectroscopy. Electrical measurements were conducted on the same samples in order to receive the sheet resistance and the capacitance values. The capacitance measurements were conducted at the top electrode of the flexible touch sensor. Finally, we will introduce the next step in the demonstration of the touch sensor, which is the application of tensile or compressive stress on the flexible touch sensor, which will result in accumulation of different capacitance.