Bio-waste onion skin as an innovative nature-driven piezoelectric material with high energy conversion efficiency

Development of non-toxic, ultra-sensitive, and flexible bio-inspired piezoelectric nanogenerator has become a great challenge for next generation biomedical applications. High performance organic/inorganic materials based piezoelectric nanogenerators suffer from several unavoidable problems such as complex synthesis and high toxicity. Biodegradable and biocompatible piezoelectric material is utmost needed in in-vivo condition to harvest energy for biomedical applications. Here, we report a novel bio-piezoelectric nanogenerator (BPNG) using naturally abundant self-aligned cellulose fibrous untreated onion skin (OS) as efficient piezoelectric material having piezoelectric strength of similar to 2.8 pC/N. The fabricated OSBPNG generated output voltage, current, instantaneous power density and high piezoelectric energy conversion efficiency of approximate to 18 V, approximate to 166 nA, approximate to 1.7 mu W/cm(2), and approximate to 61.7%, respectively, and turn on 30 green LEDs by a single device under repeated compressive stress of approximate to 34 kPa and approximate to 3.0 Hz frequency. In addition, maximum output voltage (approximate to 106 V) was achieved when 6 units are connected in series, which instantaneously turns on 73 combined LEDs (30 green, 25 blue, and 18 red). OSBPNG is highly effective during throat movement such as coughing, drinking and swallowing. Furthermore, because it works at very low pressure originating from heart pulse or beat, it could be used in pacemakers and health care units. Finally, OSBPNG successfully differentiates speech signals, indicating its potential for speech recognition.