Laser-Induced Graphitization of Lignin/PLLA Composite Sheets for Biodegradable Triboelectric Nanogenerators

With the rapid development of the Internet of Things (IoT), numerous electronic devices are expected to be installed in the natural environment. Triboelectric nanogenerators (TENGs) can be reliable devices providing on-site, clean, and sustainable power generation in nature. The fabrication of metal-free, biodegradable TENGs will reduce the environmental burden and disposal cost after usage. In this study, we demonstrate the direct fabrication of conductive graphitic carbon on a biodegradable polymer composite by laser-induced graphitization and apply the structures for metal-free biodegradable TENGs. Laser-induced graphitization of poly(lactic acid) (PLA) composite sheets was achieved for the first time by mixing alkaline lignin powder as a filler. The fabricated TENGs could generate electricity, and the power density reached ∼1.98 mW/m² at a load resistance of 200 MΩ when the fabricated TENG was driven at a contact frequency of ∼1 Hz and a contact pressure of 1 N. Power generation by contact with water and plants was also demonstrated, showing its applicability for power generation in natural environments. The proposed method in this study offers the facile fabrication of biodegradable devices and the development of sustainable power generation devices.