A Dual-Mode Flexible Sensor Based on the Combination of Triboelectric and Piezoresistive Sensing to Simultaneously Monitor Non-Contact/Contact Pressure

High-performance flexible sensors have broad application prospects in various fields such as robotic skin, intelligent prosthetic hands, and wearable devices. However, a single sensing type of sensor is limited by its own type and cannot adapt to different types of application scenarios. Herein, this paper proposes a dual-mode flexible sensor based on the combination of triboelectric and piezoresistive sensing (TRS) to simultaneously monitor noncontact/contact pressure in real time. In the triboelectric sensing mode, the object proximity distance can be determined by its voltage and current outputs, and the sharpness can be further judged by the electrode array. It can realize the accurate detection of distance within 2 cm of the object proximity distance, and it can generate a voltage signal of 2.75 V when the minimum proximity distance of the object is 0.5 cm. In the piezoresistive sensing mode, the sensing performance is optimized by adding a pyramid microstructure on the surface of the piezoresistive layer, making its sensitivity reach −0.1147 kPa at a pressure of 0–6 kPa and having high dynamic response and stability in repeatability testing. The combination of the two modes solves the problem of difficulty in accurately sensing pressure signals and noncontact signals for a single type of sensor. In practical applications, the system has been used to identify two states of object proximity and pressure and has shown ideal performance. This provides strategies and references for further expanding the application scenarios of flexible sensors and has broad application prospects in providing stronger human–machine interaction interfaces.