Wearable Triboelectric Nanogenerator (Copper TENG) Based Energy Harvester for Biosensing Applications

Energy harvesters have emerged as a promising technology, offering a sustainable alternative to traditional battery-powered systems. Recent trends in energy harvesting technology are focused on increasing power efficiency and integration in daily use applications. Triboelectric nanogenerators (TENGs) have shown a wider and a green approach to harness mechanical energy from environment and convert it into usable electrical power. This research highlights on the design and fabrication of a simple and low-cost TENG designed with copper mesh and polydimethylsiloxane (PDMS) focusing on its ability to sense mechanical force and convert it to electrical power/energy. Here, we have developed a fabrication method the fabrication method, which is simple yet efficient, without using complex chemical/mechanical processes, making it economical, sustainable and accessible. The copper, known for its excellent conductivity and flexibility, serves as an electrode to offer charge collection and transfer. We have utilized the commercially available copper mesh with different thickness for this. PDMS, a biocompatible polymer, provides high elasticity to maximize the effect of triboelectric effect. The copper mesh and PDMS are arranged in a contact separation working mode with a PDMS wall (which behaves like an air gap). This PDMS wall separates the conducting bottom copper electrode and insulator middle PDMS thin layer. The design adopts a box-and-a-lid configuration where the copper mesh along with the PDMS wall forms the box structure and the top copper electrode along the middle PDMS layer forms the lid of the device structure. The device is encapsulated with top and bottom layers of PDMS and when the triboelectric layers come in contact, they produce a change in electric potential and induce electrostatic induction to generate electrical power [1]. Experimental data demonstrates that the copper mesh-PDMS TENG can generate open circuit voltage ranging from 1 to 10 V even with gentle tapping with finger. The test devices are made with a PDMS wall of thickness 2 mm and the top and bottom PDMS encapsulating layers are made 1mm thick. The TENG device shows a linear relationship of applied pressure with voltage under constant controlled force and human finger tapping. A power density ranging from 12 µW/m2 can be achieved using 100 µm and 150 µm thick copper mesh with application of controlled constant force. The copper-TENG device shows a good potential for mechanical energy harvester as it can detect small changes in external pressure applied on it and its performance remains stable even after 4000 cycles. The device can be adhered onto the skin as it is lightweight and flexible. The future work is aimed at optimizing the device design for generating higher power capacity and integrating an energy storage element for making it suitable for powering low-power wearable biosensing devices and for IoT applications.<br/><br/>References:<br/>[1] L. Zhao, Zihong. L, and K.W.C. Lai, “Skin-integrated, stretchable triboelectric nanogenerator for energy harvesting and mechanical sensing,” <i>Materials Today Electronics</i>, vol.2, no.2, pp.1-8, Oct. 2022. doi: 10.1016/j.mtelec.2022.100012<br/>[2] M. Pan, Y. Chengang , J. Zou, Z, Y. Zhang and C. Bowen, “Triboelectric and Piezoelectric generators for Future Soft Robots and Machines,” <i>iScience</i>, vol.23, pp. 101682, 2020. doi:10.1016/j.isci.2020.101682<br/>[3] B. Bakchi, et al., “Flexible triboelectric nanogenerators using transparent copper nanowire electrodes; energy harvesting, sensing human activities and material recognition,” <i>Materials Horizon</i>, vol.10, 2023, doi: 10.1039/D3MH00404