Double Layer Methylcellulose Substrate-Based Wearable Touch Sensor and Display for Communication

In recent years, flexible printed circuit boards (FPCBs) with polyimide substrates have been widely used in electronic devices for industrial and academic research owing to their light weight, high dielectric constant, and flexibility. However, these FPCBs have a critical limitation of recycling, as polyimide is not degradable or eco-friendly. To overcome this issue, we fabricated cellulose-based FPCBs. A transparent and flexible methyl cellulose-based substrate was produced through a simple solvent evaporation process. The interconnect electrode was fabricated with a pattern of Ag/carbon nanotube composite by using a stencil mask. The methyl cellulose-based FPCBs were evaluated for diverse mechanical stresses such as bending, torsional, and tensile stresses. In addition, their surface morphology was analyzed using optical microscopy and scanning electron microscopy. For the electrical properties, in addition to the current–voltage curves, their dielectric properties were analyzed. Finally, we reported the successful wearable communication device of the cellulose-based FPCBs in a 5 × 5 touch panel and a 5 × 5 light-emitting diode display.