Lead-Free Perovskite Nanowire-Employed Piezopolymer for Highly Efficient Flexible Nanocomposite Energy Harvester.

In the past two decades, mechanical energy harvesting technologies have been developed in various ways to support or power small-scale electronics. Nevertheless, the strategy for enhancing current and charge performance of flexible piezoelectric energy harvesters using a simple and cost-effective process is still a challenging issue. Herein, a 1D-3D (1-3) fully piezoelectric nanocomposite is developed using perovskite BaTiO3 (BT) nanowire (NW)-employed poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) for a high-performance hybrid nanocomposite generator (hNCG) device. The harvested output of the flexible hNCG reaches up to ≈14 V and ≈4 µA, which is higher than the current levels of even previous piezoceramic film-based flexible energy harvesters. Finite element analysis method simulations study that the outstanding performance of hNCG devices attributes to not only the piezoelectric synergy of well-controlled BT NWs and within P(VDF-TrFE) matrix, but also the effective stress transferability of piezopolymer. As a proof of concept, the flexible hNCG is directly attached to a hand to scavenge energy using a human motion in various biomechanical frequencies for self-powered wearable patch device applications. This research can pave the way for a new approach to high-performance wearable and biocompatible self-sufficient electronics.

A flexible energy harvester based on a lead-free and piezoelectric BCTZ nanoparticle-polymer composite.

Lead-free piezoelectric 0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Zr0.2Ti0.8)O3 (BCTZ) nanoparticles (NPs) composed of earth-abundant elements were adopted for use in a flexible composite-based piezoelectric energy harvester (PEH) that can convert mechanical deformation into electrical energy. The solid-state synthesized BCTZ NPs and silver nanowires (Ag NWs) chosen to reduce the toxicity of the filler materials were blended with a polydimethylsiloxane (PDMS) matrix to produce a piezoelectric nanocomposite (p-NC). The naturally flexible polymer-based p-NC layers were sandwiched between two conductive polyethylene terephthalate plastic substrates to achieve a flexible energy harvester. The BCTZ NP-based PEH effectively generated an output voltage peak of ∼15 V and a current signal of ∼0.8 µA without time-dependent degradation. This output was adequate to operate a liquid crystal display (LCD) and to turn on six blue light emitting diodes (LEDs).

The effects of propionic acid on nano-sized BaTiO3 particles synthesized by a hydrothermal method.

The influence of propionic acid on BaTiO3 particles prepared via hydorthermal method is discussed. The amount of the acid is varied in the experimental processes to enhance understanding of the roles of the propionic acid. Smaller sized BaTiO3 powders with more uniform particle sizes can be achieved at 200 degrees C after 24 h using propionic acid. The acid is found to be excellent for size reduction and narrow size distribution. Reitveld refinement of the XRD patterns revealed that the synthesize BaTiO3 nanopowders have tetragonal asymmetry dominant structures. The "micro-capsules" caused by the acid are observed using high temperature in-situ TEM analysis. High vacuum condition of the TEM is attributed to the notable differences. It can thus be posited that the reduction of particle size and the narrow size distribution result from the "micro-capsule" effects of propionic acid. Moreover, the "capsules" are attributed to a decrease of intragranular pores in the BaTiO3 particles.