Flexible resistive pressure sensor with silver nanowire networks embedded in polymer using natural formation of air gap

A new type of flexible pressure sensor with air gap has been designed based on polydimethylsiloxane (PDMS) and silver nanowires (AgNWs). During fabrication, the interdigitated Ag electrode was fabricated on the bottom PDMS layer by doctor blading and AgNWs were embedded in the top PDMS layer, with a naturally formed air gap between the AgNW layer and the interdigitated electrodes. The thus -formed air gap was controlled by the number of AgNW layers and played an important role in enhancing sensitivity by decreasing the off current in the absence of pressure. The maximum sensitivity of 16.1 kPa(-1) was obtained via optimization of the air gap thickness, the AgNW sensing area, and the channel length of the electrodes. The stability of the sensors was confirmed by durability, repeatability, bending, and hysteresis tests. The pressure sensor based on the highly sensitive AgNW network could provide a great opportunity for measuring various types of forces and displacements in wearable devices.