Piezoelectric Nanomesh-Empowered Skin-Attachable Capacitive Auditory Sensor

Wearable auditory sensors hold vast potential in the upcoming Internet of Things (IoT) era for their use in sound-driven smart home, healthcare, and human-machine interface applications. In this work, a piezoelectric polyvinylidene fluoride (PVDF)-based nanomesh is exploited as a self-charge generating diaphragm to power a skin-attachable capacitive auditory sensor. The piezoelectric nanomesh is self-poled <i>via</i> a simple, scalable electrospinning fabrication process, eliminating the need for an additional cumbersome high voltage poling procedure. The deformation-induced charges in the piezoelectric nanomesh generate an electric field between two capacitive electrodes, supplying the bias voltage crucial for the operation of capacitive sensors. Importantly, this reduces the necessity of a bulky power source or environmentally susceptible electrets, which has remained a critical limitation of capacitive auditory sensors to date. Moreover, combined with its inherent porous structure and enhanced mechanical flexibility, the piezoelectric nanomesh allows the sensor to exhibit a flat frequency response (100-3000 Hz), good linearity (50-75 dB_SPL), and a high signal-to-noise ratio (SNR) (≥30 dB). Once attached to human skin, e.g., the neck, the auditory sensor successfully detects and decouples various acoustic information, including voice, gulping, and coughing, showing significant potential as a next-generation electronic skin for voice biometrics, human-machine interfaces, and mobile healthcare.