Flexible, Stretchable, and Antifreezing Triboelectric Nanogenerators Based on Cellulose Hydrogel for Energy Harvesting and Wearable Electronics

Because of the increasing popularity of self-powered devices that use environmental or mechanical energy harvesting, triboelectric nanogenerators (TENGs) can be used as power sources in wearable electronic devices. However, the preparation of stretchable and flexible TENGs with outstanding electrical output performance is a challenge that requires further investigation. In this study, multiwalled carbon nanotubes (MWCNTs)/cellulose nanofibrils (CNFs)/poly(vinyl alcohol) (PVA) hydrogel-based TENGs that are stretchable, antifreezing, and highly conductive were developed. Doping of multiwalled carbon nanotubes and cellulose nanofibrils promotes the cross-linking of the hydrogel and the formation of microchannels within it, which not only improves ion transport to enhance hydrogel conductivity but also increases the triboelectric output through streaming potential. As the hydrogel is compressed, 2% MWCNTs hydrogel-based TENGs would generate an open-circuit voltage of 160 V in contact-separation mode and an induced voltage of 6.1 V was obtained via the streaming potential mechanism. A wearable sensor for motion detection was also developed using TENGs with outstanding stretchability and flexible performance. Because of their high sensitivity and effective mechanical energy-harvesting capabilities, ionic hydrogels hold promise for the development of next-generation, advanced wearable electronic devices.