A button switch inspired duplex hydrogel sensor based on both triboelectric and piezoresistive effects for detecting dynamic and static pressure

The capability to sense complex pressure variations comprehensively is vital for wearable electronics and flexible human-machine interfaces. In this paper, inspired by button switches, a duplex tactile sensor based on the combination of triboelectric and piezoresistive effects is designed and fabricated. Because of its excellent mechanical strength and electrical stability, a double-networked ionic hydrogel is used as both the conductive electrode and elastic current regulator. In addition, micro-pyramidal patterned polydimethylsiloxane (PDMS) acts as both the friction layer and the encapsulation elastomer, thereby boosting the triboelectric output performance significantly. The duplex hydrogel sensor demonstrates comprehensive sensing ability in detecting the whole stimulation process including the dynamic and static pressures. The dynamic stress intensity (10-300 Pa), the action time, and the static variations (increase and decrease) of the pressure can be identified precisely from the dual-channel signals. Combined with a signal processing module, an intelligent visible door lamp is achieved for monitoring the entire "contact-hold-release-separation"state of the external stimulation, which shows great application potential for future smart robot e-skin and flexible electronics.