A new multifunctional energy harvester based on mica nanosheet-dispersed PVDF nanofabrics featuring piezo-capacitive, piezoelectric and triboelectric effects

Abstract

In recent years, there has been a significant rise in the popularity of piezoelectric and triboelectric nanogenerators as alternative power sources for miniature devices and internet of things devices (IoT). Herein, piezoelectric nanogenerators (PNG) and triboelectric nanogenerators (TENG) based on mica nanosheet (MNS)-infused poly(vinylidene fluoride) (PVDF) composite nanofabrics were developed. The morphology, crystallinity, and polymorphism of PVDF/MNS composite nanofabrics were studied using different characterization techniques. The incorporation of MNS into PVDF resulted in enhanced electroactive β-phase content, reaching a maximum of 84.3% in the composite nanofabric containing 0.75 wt% of MNS. The same nanofabric exhibited a dielectric constant ∼1.64 times that of pure PVDF nanofabric, substantially enhancing the capacitive sensing capability by ∼4.4 times. The PNG developed using the nanofabric containing 0.75 wt% of MNS displayed an open-circuit voltage (V_OC) of ∼8.4 V and a power density of ∼3 μW cm⁻² when subjected to 8 N force. The TENG based on the aforementioned nanofabric produced a maximum V_OC of ∼163 V and a power density of ∼585 μW cm⁻² when subjected to one-finger tapping. With the same TENG upon one-finger tapping, 35 LEDs were illuminated. A fluttering-driven TENG utilizing the same nanofabric generated a maximum V_OC of ∼70 V when exposed to a wind speed of 7 m s⁻¹. The results indicate that the nanofabrics developed herein could potentially be utilized to fabricate energy harvesting devices to power health monitoring sensors, IoT and nano/micro devices.