Engineering Polymer Interfaces Toward Controlling Triboelectric Surface Charge for Wearable Systems

Developing pathways and materials that efficiently convert ambient energy from the environment into electricity is critical to powering distributed sensing networks, wearable and implantable electronics, and other Internet of Things (IoT) devices.[1] Mechanical and kinetic motions exist everywhere in our society, from human movement, blood flow, railway vibrations, car vibrations, rain fall bicycle motion, geological activity, or even simply water flowing through pipes. This abundance of motion has led to an explosion of research in small–scale mechanical energy harvesters.The goal of these mechanical energy harvesting technologies is to extract electrical energy from an otherwise stable material and convert it into useable electricity. Adding functionality where a certain material can also harvest heat and/or light can also boost energy generation and reduce energy loss.[2] Generally, such harvesting is practical to autonomously power low-energy devices (µW–mW).<br/>Triboelectric energy harvesting devices, or so called triboelectric nanogenerators (TENG), have recently gained momentum for mechanical energy harvesting to power autonomous microdevices and portable electronics. Polymer-based TENGs can be easily fabricated from cheap, lightweight, flexible, and abundantly available materials. In comparison to piezoelectric, ferroelectret, and piezoelectrochemical principles, TENGs do not require costly materials or processes to enable energy harvesting, although significant developments are overcoming some difficulties in some piezoelectric polymer systems.<br/>In our research within the field of TENG, we have explored the intricate nature of triboelectric charging in polymers and elucidated various strategies for enhancing the performance of TENGs. Our investigations into triboelectric surface charge engineering have encompassed a range of material factors operating at the nanoscale. Key factors we have examined include: Triboelectrification Mechanisms: We have delved into the mechanisms underlying triboelectrification, which encompass mass transfer, ion transfer, and electron transfer processes.<br/>Effect of Surface Roughness: Our studies have investigated how surface roughness influences charge generation, shedding light on its crucial role in TENG performance.Temperature Influence: We have explored the impact of temperature on charge generation, providing valuable insights into optimizing TENG operation under varying environmental conditions. Influence of Fillers: Our research has examined how the presence of fillers within polymers affects charge generation, uncovering strategies to enhance TENG efficiency.<br/>Adhesion and Surface Properties: We have analyzed the interplay of adhesion and surface properties in charge generation, emphasizing their significance in TENG design. Polymer Chemistry and Bond Energy: Our investigations have considered the role of polymer chemistry and bond energy in triboelectric charging processes, offering a comprehensive view of material design.Collectively, these multifaceted aspects have culminated in the development of a flexible wearable triboelectric nanogenerator capable of achieving remarkable results, including a peak power output of 24 mW m^-² and energy generation of 4.5 mJ. This underscores the potential for harnessing TENG technology in wearable applications and beyond.<br/><br/>1. A. Corletto, A. V. Ellis, N. A. Shepelin, M. Fronzi, D. A. Winkler, J. G. Shapter, P. C. Sherrell, <i>Adv. Mater.</i> 2022, 34, 2203849.<br/>2. F.-R. Fan, Z.-Q. Tian, Z. L. Wang, <i>Nano Energy</i> 2012, 1, 328.