A high-performance, flexible, and dual-modal humidity-piezoelectric sensor without mutual interference

High-performance, flexible, and multifunctional humidity-piezoelectric sensors are applicable to respiratory pattern detection, man-machine motion distinction, and dual-modal speech recognition. However, signal disturbances between the humidity and pressure signals remain, and interference from the external environment such as temperature further results in signal vibrations. In this study, a high-performance, flexible, and dual-modal humidity-piezoelectric sensor is introduced to achieve accurate and stable sensing signals by fully prohibiting mutual interference towards simultaneous humidity and pressure stimuli. It is first designed using a high-performance humidity-sensing unit constructed by polyacrylate sodium (PAAS)/carbon nanotube (CNT) film and a piezoelectric sensing unit formed by polyvinylidene fluoride (PVDF)/CNT nanofiber film. The patterned PAAS/CNT unit exhibits a resistance change of 1100 % in relative humidity of 23 %–98 %, minor hysteresis, favorable durability, and negligible pressure interference. The PVDF/CNT piezoelectric unit demonstrates a sensitivity of 0.11 V/kPa in a wide pressure range of 3–115 kPa, good linearity, high durability, negligible humidity and temperature interference, and fully prohibited signal noise. Moreover, the high-performance, flexible, dual-modal humidity-piezoelectric sensors display significant applications for man-machine motion detection, human gestures and object distinction, and dual-modal speech recognition.