A Highly Sensitive Bending Sensor Based on Controlled Crack Formation Integrated with an Energy Harvesting Pyramid Layer

A highly sensitive bending sensor composed of patterned Pt lines, integrated with energy harvesting capability, is reported. The sensitivity of the bending sensor increases as the width of the Pt lines decreases, owing to the increase in crack density with decreasing line width. Furthermore, sensitivity increases with increasing bending cycles, but saturates at around 1000 cycles. Such a behavior corresponds to the increase and eventual saturation of crack density with increasing bending cycles. A microstructured polydimethylsiloxane layer is placed on top of the Pt lines to serve as a triboelectric energy harvesting layer, where human skin and the Pt lines are utilized as electrodes. Voltage and current of 18.6 V and 209 nA are generated, respectively, from gentle finger tapping. These demonstrations make the device highly useful for a wide variety of portable and wearable flexible electronic applications.