Water flow and finger-tapping mediated piezoelectric energy generation using a natural hematite-based flexible PVDF-HFP membrane

Energy demand is increasing exponentially nowadays, which is the primary cause of the burning of fossil fuels, creating enormous amounts of environmental degradation. To arrest this, there is an emerging need for clean and green technologies. Herein, piezoelectric materials have become a favourite choice among scientists. Previously, many groups have exploited this fascinating technology by imparting pressure from different available sources. This article deals with gadolinium (Gd)-incorporated naturally occurring hematite nanocrystals, which show an efficient piezoelectric effect when incorporated into a PVDF-HFP polymer. In reality, PVDF-HFP is capable of producing nominal piezoelectric polarization (40-60% beta-polarization), which in our case is found to be around 80.3%. Such elevated polarizability helps to generate piezoelectric power under water flow or finger tapping. This reported material is not only flexible and bendable but can also produce maxima of 16.92 V and 0.52 mu A instantaneous voltage and current, respectively, under simple finger tapping, but 8 V under flowing water. Moreover, these phenomena have been discussed and analyzed in great depth by involving various characterization tools such as XRD, FESEM, TEM, FTIR, and zeta potential. This is probably the first time that a rare-earth-incorporated natural nano-rock mineral has been used to fabricate such a multifunctional device. Piezoelectric energy generation using finger tapping and non-invasive water flow as mechanical stimuli by a Gd3+-doped natural hematite rock-based flexible free-standing PVDF membrane.