Silk fibroin-based biodegradable piezoelectric composite nanogenerators using lead-free ferroelectric nanoparticles

Silk fibroin-based biodegradable composite-type nanogenerators are demonstrated with controllable lifetime for powering to the implantable devices. The 2D thin film- and 1D wire-type composites consist of the well-dispersed lead-free ferroelectric (BaTiO3, ZnSnO3, Bi-0.5(Na(0.82)k(0.18))(0.5)TiO3, and K0.5Na0.5Nb0.995Mn0.005O3) nanoparticles. Ag nanowires are used to enhance the dispersion of the nanoparticles and polyvinylpyrrolidone prevents Ag nanowires from connecting with each other. A maximum output voltages and current densities of 2.2 V and 0.12 mu A/cm(2) in the thin film, and 1.8 V and 0.1 mu A/cm(2) in the wire are obtained under the motion of a foot step for when 30 wt% KNN:Mn nanoparticles are well-dispersed in the solution because of the largest piezoelectric coupling figure of merit. The properties of water-soluble composite films are also controlled with the glycerol content up to two days. (C) 2015 Elsevier Ltd. All rights reserved.