Sustainable Triboelectric Nanogenerators Suitable for Low-Power Wearables

Triboelectric nanogenerators (TENGs) have attracted significant attention as energy-harvesting devices due to their lightweight structure, mechanical flexibility, simple fabrication, and ability to convert low-frequency mechanical motion into electrical energy. TENGs show particular promise for powering micromachines and biosensors through biomechanical energy harvesting. However, high-output devices typically rely on synthetic tribomaterials [i.e., polytetrafluoroethylene (PTFE) and nylon], which, despite their strong electrostatic properties, are nonbiodegradable and derived from nonrenewable sources. Developing entirely renewable TENGs capable of generating functional electrical output remains an important materials challenge. In this work, complementary triboelectric layers were fabricated exclusively from renewable biopolymers: chitosan and sodium alginate, formed into elastomeric films. The electrostatic difference between the tribopositive and tribonegative layers was evaluated throughout the incorporation of natural deep eutectic solvent (NADES) plasticizers and a water-soluble conductive polymer (pPDS), respectively. The resulting double-electrode contact–separation TENG delivered a power density of 0.147 μW/cm2 with voltage outputs approaching 1.5 V. To provide a rigorous reference framework for evaluating these emerging alternatives, TENGs employing standard synthetic tribolayers (PTFE and nylon), as well as a hybrid biopolymer/synthetic polymer and fully biopolymer configurations, were systematically developed and tested. As widely recognized gold-standard tribomaterials, PTFE and nylon serve as established benchmarks for the triboelectric performance, which achieved peak power densities of up to 2.2 μW/cm2 and maximum voltages of approximately 15 and 100 V, respectively. The comparative analysis positions the developed biopolymer elastomers within the triboelectric series and demonstrates that fully renewable systems can generate sufficient output for low-energy electronics and self-powered sensing applications. This work establishes a foundation for future application-oriented designs of fully sustainable triboelectric devices as viable alternatives to conventional TENG systems.