Upcycling Emperor Fish Scales for Biocompatible Piezoelectric Energy Harvesting

Tons of fish waste is discarded from many foods processing industries which are indeed a good source of collagen which exhibits piezoelectric properties. Collagen is found in the scales, skin, fin, bladder bones of the fishes. Among these, the scales contain the maximum proportion of glycine composition. This article reports a systematic procedure based on chemical treatments to extract collagen from fish scales and incorporate in polydimethylsiloxane polymer, which is also biocompatible to develop the flexible, biocompatible piezoelectric harvester. The unpoled energy harvester can deliver an output voltage of 5 V, the short circuit current of 30 mA, and a corresponding maximum output power density of 649 mW/cm2 with a load resistance of $100\ \Omega$ under compressive stress applied at a frequency of 30 Hz. Such biocompatible energy harvesters are highly suited for human body-attached solutions that could harvest energy from gait and the hand-arm movement.