Self-powered wire type UV sensor using in-situ radial growth of BaTiO3 and TiO2 nanostructures on human hair sized single Ti-wire

A flexible, non-planar, human hair sized [Diameter (Ø) ≈100 μm, Length (L) ≤6 cm] Ti-wire/BaTiO3 (BTO) core-shell nanostructures (NSs) was developed using chemical oxidation-modification (COM) method followed by a low-temperature hydrothermal technique. COM method of flexible/non-flexible Ti-wires (Ø ≈ 800 μm, 100 μm) outer surface generates uniform distribution/continuous radial growth of TiO2 nanoneedles/nanoparticles having anatase crystalline phase. Photo-responsive performance investigated by fabricating the TiO2 NSs/Ti wire (TW) based UV sensors as a function of fixed bias voltages (±1 V and ±7 V) under various light sources having wavelengths (λ) 365 nm, 405 nm and 535 nm. TW-UV sensor (Ø ≈ 800 μm) has higher photo-responsivity ≈35.024 μA/W than the TW-UV sensor (Ø ≈ 100 μm) under the light intensity ≈18 mW/cm2 (λ ≈ 365 nm) at bias voltage ≈−1 V, respectively. Further, the XPS spectra of the tetragonal crystalline phase of radially grown BTO NSs confirms the presence of Ba 2+ and Ti +4 oxidation states directly connected to the internal stresses of TiO6 octahedron in BTO lattice. Next, flexible wire based piezoelectric nanogenerator (FW-PNG) was fabricated to harness the mechanical energy, biomechanical motions into useful electrical energy. Realized self-powered UV sensor by the parallel connection between FW-PNG and TW-UV sensor as a function of constant mechanical load (2 N) under various light intensities (18, 40 and 60 mW/cm2) of source wavelength 365 nm, respectively. This study can pave the way for developing micro/nanodevices on non-planar mechanical structures; human hair sized energy harvesters and self-powered sensors.