The investigation of the energy harvesting performance using electrospun PTFE/PVDF based on a triboelectric assembly

Abstract

Abstract This work presents an investigation into the energy harvesting performance of a combination of PTFE and PVDF materials prepared using a one-step electrospinning technique. Before electrospinning, different percentages of the 1-micron PTFE powder were added to a PVDF precursor. The surface morphology of the electrospun PTFE/PVDF fibre was investigated using a scanning electron microscope (SEM) and tunnelling electron microscope (TEM). The structure was investigated using Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction analysis (XRD). A highly porous structure was observed with a mix of the α- and β-phase PVDF. The amount of β-phase was found to reduce when increasing the percentage of PTFE. The maximum amount of PTFE that could be added and still be successfully electrospun was 20%. This percentage showed the highest energy harvesting performance of the different PTFE/PVDF combinations. Electrospun fibres with different percentages of PTFE were deployed in a triboelectric energy harvester operating in the contact separation mode and the open circuit voltage and short circuit current were obtained at frequencies of 4 to 9 Hz. The 20% PTFE fibre showed 4 (51 to 202 V) and 7 times (1.3 to 9.04 µA) the voltage and current output respectively when compared with the 100% PVDF fibre. The Voc and Isc were measured for different load resistances from 1kΩ to 6GΩ and achieved a maximum power density of 348.5 mW/m2 with a 10 MΩ resistance. The energy stored in capacitors 0.1, 0.47, 1, and 10 µF from a book shaped PTFE/PVDF energy harvester were 1.0, 16.7, 41.2 and 136.8 µJ, respectively. The electrospun fibre is compatible with wearable and e-textile applications as it is breathable and flexible. The electrospun PTFE/PVDF was assembled into shoe insoles to demonstrate energy harvesting performance in a practical application.