Exclusive β-phase, piezoelectric PVDF thin films with high d ₃₃ (−49.6 pm V ⁻¹ ) synthesised via low temperature quenching.

Utilising an interfacial piezoelectric ZnO nanosheet layer, a significant enhancement in the power density is\ud reported for the triboelectric nanogenerators (TENG) based on phase inversion membranes of polyvinylidene\ud fluoride (PVDF) and polyamide-6 (PA6). At an applied force of 80 N, the TENG device incorporating electrochemically\ud deposited ZnO nanosheets produces an output voltage of ~ 625 V and a current density of ~\ud 40 mA m−2 (corresponding a charge density of 100.6 μC m−2), respectively; significantly higher than ~ 310 V\ud and ~ 10 mA m−2 (corresponding a charge density of 77.45 μCm−2) for the pristine TENG device. The enhancement\ud in the surface charge density provided by the interfacial piezoelectric ZnO layer is also reflected in\ud the high piezoelectric coefficient d33 (−74 pm V−1) as compared to the pristine fluoropolymer membranes\ud (−50 pm V−1). For tribo-negative membranes incorporating the interfacial ZnO layer, piezoelectric force microscopy\ud measurements further show enhanced domain size which can be attributed to the interfacial dipoledipole\ud interaction with the ferroelectric polarisation of PVDF, which promotes the alignment with the polar axis\ud of ZnO. Under compressive stress, the piezoelectric potential thus produced in the ZnO nanosheets provides\ud charge injection on to the surface of ZnSnO3-PVDF membrane, improving the charge density, which in-turn\ud significantly enhances the power density from 0.11 to ~ 1.8 W/m2. The TENG devices thus fabricated using a\ud facile electrochemical deposition and phase inversion technique show enhanced output power without the need\ud for high electric field poling or external charge injection process by relying on the coupling of triboelectric and\ud piezoelectric effects

Photo-curable nanocomposite material was formulated by embedding ZnO nanoparticles into a SU-8 matrix and studied for its piezoelectric properties for low cost fabrication of self-powered nanodevices. The piezoelectric coefficient of ZnO nanoparticles was observed to be ranging between 15 and 23 pm/V, which is the highest reported. These experimental studies support the recent theoretical predictions where the piezoelectric coefficients in ZnO nanoparticles were found to be higher compared to the thin films because of the surface relaxation induced volume reductions in the nanometer scale. The photo-curable property of these polymer composite films is exploited to demonstrate fabrication of a micro-cantilever test structure.