Repeatedly Bendable Paper Touch Pad via Direct Stamping of Silver Nanoink With Pressure-Induced Low-Temperature Annealing

We report fabrication of mechanically bendable touch sensor pads by direct stamping of nanoinks with silver nanoparticles (AgNPs) dispersed in an organic solvent. Direct stamping lowers annealing temperature of silver nanoparticles and enhances mechanical flexibility. The directly stamped silver electrode reaches the silver nanoink's final conductivity at lower annealing temperature, 130 °C, than the As-sprayed silver electrode. And also the directly stamped silver electrodes have much lower resistance than the As sprayed one even before annealing of AgNPs. In addition, the touch sensor pads fabricated by direct stamping shows no significant decrease in sensitivity even after repeated bending stroke test at 1 Hz for 10 000 cycles. These results of mechanical stability and low annealing temperature are possible because the compressive force, which is applied to the AgNPs inside the trenches of a stamp during the direct stamping process, induces removal of pores between neighboring AgNPs, and subsequent, densification of the layers of AgNPs.