Nanosheet-Doped Polymer Composites with High Intrinsic Piezoelectric Properties for Energy Harvesting

Few-layer nanosheets (NSs) of hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS₂) display notable piezoelectric properties. Yet, their integration into polymers typically yields non-piezoelectric composites due to NSs' random distribution. We introduce a facile method for fabricating intrinsic piezoelectric composites incorporated with NSs without electric poling. Our innovative process aligns NSs within polyvinyl alcohol polymer, leveraging ice-water interfacial tension, water crystallization thrust, and directional cross-linking during freezing. The resulting PE composites exhibit a maximum piezoelectric coefficient of up to 25.5–28.4 pC N⁻¹, comparable to polyvinylidene difluoride (PVDF), with significant cost-efficiency, safety, and scalability advantages over conventional materials. Using this composite, we develop highly sensitive wearable pressure and strain sensors, and an ultrasound energy harvester. These sensors detect finger bending and differentiate between walking and running, while the harvester generates ~1.18 V/2.31 μA under 1 W cm⁻² ultrasound input underwater. This universal method offers a novel manufacturing technique for piezoelectric composites, demonstrating remarkable effectiveness in synthesizing intrinsic piezoelectric composites based on 2D materials. Moreover, its potential extends to applications in wearable electronics and energy harvesting, promising significant advancements in these fields.