Flexible Triboelectric Laminates—Energy Harvesters for Wearable Electronics

Triboelectric nanogenerator (TENG) devices have attracted considerable interest in the field of mechanical energy harvesting due to their low weight and mechanical softness. There are many innovative TENG devices from low-cost materials presented in the literature for mechanical energy harvesting from human motion, vibrations, wind, water flow, and waves[1].<br/>Herein we report a new paradigm of triboelectric polymers – the triboelectric laminate – a volumetric material with electromechanical response comparable to the benchmark soft piezoelectric material polyvinylidene difluoride. The electromechanical response in the triboelectric laminate arises from aligned dipoles, generated from orientation of contact electrification in the laminates bulk volume. The triboelectric laminates where the polymer bilayers with different triboelectric properties are stacked to form laminates, together with the separator between each bilayer and for an electrodes we use flexible polyisoprene conductive carbon black composite. The dipoles are forming between sequential bilayers consisting of two different polymer fibres of different diameter. The loose interface between fibre bilayers ensures friction and triboelectric charging between two polymers. The electric output from the electrospun triboelectric laminate increases with increasing the density of bilayers.Triboelectric laminate generates Volumetric energy density of 21.13 µJ cm⁻³ and a peak average power density of 46.19 µW cm⁻³ are observed from six layer laminate. Our material concept has clear benefits over the other flexible devices for mechanical energy harvesting. It does not require any poling procedures and electromechanical response is stable over 24 hours of continuous operation. Moreover, the electromechanically responsive material can be made from all types of polymers, thus providing ample of room for further improvements or functionalities such as stretchability, biodegradability, or biocompatibility. The concept of a triboelectric laminate can be introduced into existing triboelectric nanogenerator form factors, to dramatically increase charge harvesting of a variety of devices.<br/><br/>This work has been supported by the European Regional Development Fund within the Activity 1.1.1.2 “Post-doctoral Research Aid” of the Specific Aid Objective 1.1.1 “To increase the research and innovative capacity of scientific institutions of Latvia and the ability to attract external financing, investing in human resources and infrastructure” of the Operational Programme “Growth and Employment” (No.1.1.1.2/VIAA/3/19/404)<br/><br/>1.Wang, S., Lin, L. & Wang, Z.L. , "Triboelectric nanogenerators as self-powered active sensors", Nano Energy, (2015)vol. 11, pp. 436-462.