A flexible lead-free piezoelectric nanogenerator based on vertically aligned BaTiO3 nanotube arrays on a Ti-mesh substrate

A uniform piezoelectric film on a flexible substrate is highly desirable for the construction of mechanical energy harvesting devices and self-powered sensors. In this study, we synthesized piezoelectrically active tetragonal phase BaTiO3 (BTO) nanotube arrays uniformly coated on a flexible Ti-mesh substrate by in situ conversion of anodized TiO2 nanotubes using a low temperature hydrothermal process. The direct conversion of the TiO2 nanotube to tetragonal phase BTO provides an excellent way to make flexible composites with a uniform distribution and enhanced volume fraction of piezoelectrically active BTO film. Based on the merits of the tetragonal phase BTO film on a Ti-mesh substrate, a novel fully bendable and mechanically robust piezoelectric nanogenerator (PENG) was fabricated. The oriented tetragonal phase BTO nanotube film on the Ti-mesh substrate was encapsulated in a polydimethylsiloxane (PDMS) elastomeric layer and assembled between two indium tin oxide (ITO) coated polyethylene terephthalate (PET) electrodes to form a flexible PENG. The PENG device can harvest mechanical energy from repeated bending and releasing motions. The resulting output voltage and current reached up to 10.6 V and 1.1 mu A, respectively. The output power generated was sufficient to instantaneously light a full screen liquid crystal display (LCD). The Ti-mesh/BTO-based PENG device is lead-free and does not have a toxic dispersion enhancer. It is a promising candidate for self-powered sensors and biomedical device applications.