Lead-free flexible Bismuth Titanate-PDMS composites: A multifunctional colossal dielectric material for hybrid piezo-triboelectric nanogenerator to sustainably power portable electronics

This study presents a multiunit hybrid piezo-triboelectric nanogenerator (HNG), utilizing both the triboelectric and piezoelectric effects, constructed from Bismuth Titanate, Bi4Ti3O12 (BiTO)/polydimethylsiloxane (PDMS) composite films through a simple and cost-effective fabrication technique. The BiTO samples synthesized by a mixed oxide route crystallize in the orthorhombic symmetry, as confirmed by the Rietveld refinement of the structural data. The temperature- and frequency-dependent dielectric spectra elucidate the colossal dielectric properties of BiTO, originating from the combined effects of interfacial polarization, hopping polarization, and extrinsic electrode effect. The colossal dielectric BiTO leads to the amplification of internal polarization, providing enhanced output performance of the HNG device. As a result, the HNG devices exhibit multiple folds improvement in terms of power density compared to individual PDMS-BiTO composite-based PENG and TENG devices. Subsequently, a new design of device structure comprising a multiunit HNG device is constructed with the help of a 3D printed structure and a ball, delivering the voltage and current output of 300 V and 4.7 μA, respectively. Finally, the HNG device is utilized for biomechanical energy harvesting and powering various electronics like LEDs, a calculator, and a wristwatch.