Sustainable triboelectric nanogenerators based on recycled materials for biomechanical energy harvesting and self-powered sensing

Triboelectric nanogenerators (TENGs) are widely used as a novel kind of sustainable energy harvesting technique. The materials used for TENGs are diverse that include polymers, metals, inorganic and composite materials, etc. However, most of these materials are not recyclable and thus may potentially cause environmental problems. Therefore, this review aims to summarize and discuss sustainable TENGs based on recyclable materials that are largely in line with the sustainable development of our society. Specifically, this review summarizes the current progress in recycled materials based TENGs (RM-TENGs), involving the design, fabrication, evaluation and application of TENGs that are made from recycled materials. First, the current recycling methods for recycled materials are overviewed and the basic procedures in practice are outlined. Then, the energy harvesting and sensing applications of RM-TENGs are critically reviewed and discussed under different classifications of recycled materials. Their potential applications are also demonstrated. Finally, we provide perspectives on the challenges and potential solutions associated with the next-generation recycled-material based TENGs. Using recycled materials to fabricate TENG can break through the existing material limitations of TENGs, and more importantly, create a high level of sustainability by generating sustainable and renewable energies from waste materials.