Stretchable surfaces and electrodes for triboelectric nanogenerators: Challenges and opportunities

Stretchable triboelectric nanogenerators (s-TENGs) have emerged as a promising solution for sustainable conversion of mechanical energy into electrical energy. The electrical energy is generated by the combined effect of contact electrification occurring at triboelectric surfaces and the transfer of charges through the electrodes of s-TENGs which can be used for a range of applications such as self-powered sensors in Internet of Things (IoTs), sensing ambient conditions, bio medical treatments, and rehabilitation. The s-TENGs are effective in harvesting low-frequency mechanical movements (2–5 Hz), due to the low elastic modulus of their stretchable triboelectric surfaces and electrodes. Herein, a comprehensive system-level performance of both stretchable triboelectric surfaces and stretchable electrodes towards their successful deployment in s-TENGs have been reviewed. We specifically review the challenges associated with triboelectric surfaces of s-TENGs such as low charge density, environmental toxicity, limited contact area and limited lifespan. Besides, the low conductivity and the issues associated with drying, freezing and mechanical integrity of the hydrogel electrodes (HEs) as well as the challenges of agglomeration, oxidation, high surface tension of liquid metal (LM) electrodes are critically evaluated based on the published literature during the last twelve years (2013 – 2025). Significant research gaps have been identified despite substantial research towards performance enhancement for the realization of practical TENGs. Initiatives required to practically deploy s-TENGs and a roadmap towards this goal also have been discussed.