High-performance piezoresistive sensors based on transfer-free large-area PdSe₂ films for human motion and health care monitoring

Two-dimensional transition metal dichalcogenides (TMDs) are needed in highperformance piezoresistive sensors due to their strong strain-induced bandgap modification and thereby large gauge factors. However, integrating a conventional high-temperature chemical vapor deposition (CVD)-grown TMD with a flexible substrate necessitates a transfer process that inevitably degrades the sensing properties of the TMDs and increases the overall fabrication complexity. We present a high-performance piezoresistive strain sensor that employs largearea PdSe2 films grown directly on polyimide (PI) substrates via plasma-assisted selenization of a sputtered Pd film. The reliable strain transfer from the substrate to the PdSe2 film ensures an outstanding strain-sensing capability of the sensor. Specifically, the sensors have a gauge factor of up to 315 +/- 2.1, a response time under 25 ms, a detection limit of 8 x 10(-6), and an exceptional stability of over 10(4) loading-unloading cycles. By attaching the sensors to the skin surface, we demonstrate their application for measuring physiological parameters in health care monitoring, including motion, voice, and arterial pulse vibration. Furthermore, using the PdSe2 film sensor combined with deep learning technology, we achieved intelligent recognition of artery temperature from arterial pulse signals with only a 2% difference between predicted and actual temperatures. The excellent sensing performance, together with the advantages of low-temperature fabrication and simple device structure, make the PdSe2 film sensor promising for wearable electronics and health care sensing systems.