Biomimetic Heteromodulus All-Fluoropolymer Piezoelectric Nanofiber Mats for Highly Sensitive Acoustic Detection

Flexible piezoelectric pressure sensors have aroused a plethora of applications in wearable electronics, acoustic transducers, and energy harvesters thanks to many merits such as prompt response, good signal linearity, and ease of shaping. However, as all-polymer piezoelectric films have a low piezoelectric coefficient and severe stress dissipation, it is currently challenging to achieve a high piezoelectric output for the foregoing applications without introducing nanomaterials or piezoelectric ceramics. Here, we report a local stress engineering strategy to fabricate biomimetic all-fluoropolymer piezoelectric film pressure sensors with high-modulus poly(vinylidene fluoride) (PVDF) nanospheres embedded on low-modulus poly(vinylidene fluoride-trifluoride ethylene) (PVDF-TrFE) nanofibers for highly sensitive acoustic detection. High-modulus PVDF nanospheres create many local stress concentration sites on PVDF-TrFE nanofibers and increase the local deformation, leading to significantly improved force/pressure sensitivity. As such, by comparison with the force sensitivity of 60 mV/N for neat PVDF-TrFE, the heteromodulus fiber mats with 10 wt % PVDF nanospheres can achieve a force sensitivity of 145.1 mV/N over 0-25 N dynamic impact force (i.e., 0 ∼ 250 kPa pressure), together with an acoustic detection limit as low as 60 dB or 0.02 Pa.