Wood-Derived Lignocellulosic Nanofibrils Based Triboelectric Nanogenerator for Electronic Integration

Triboelectric nanogenerators (TENGs) are a transformative energy harvesting technology owing to their high-power output, simple architecture, small size, and low cost. They are highly promising to provide embedded powering capabilities to next-generation of disposable wearable electronics (i.e. as part of glasses, shoes, or fabrics) that are completely autonomous. TENGs generate electrical energy by harvesting chaotic and low frequency mechanical energy from environmental or human motions (i.e. waves, wind, walking, running) through the coupling of triboelectric effect and electrostatic induction.<br/>To date, PTFE and other fluorinated polymers accounted for negative tribolayers in more than 50% of reported TENGs in the literature. However, there are growing global interests in replacing petroleum-based non-biodegradable plastics by green natural materials to attain a higher sustainability and a lower environmental impact. As a result, (ligno)cellulose, ubiquitous as a low-cost, renewable, biocompatible, and biodegradable material, has attracted significant attentions. Previous studies demonstrated the potential of using renewable lignocellulosic materials as the tribopositive layer replacing other common tribopositive substrates (such as metals, metal oxides, and petroleum-based polymers).<br/>Here, we report the discovery of a natural tribonegative material, LCNFs, wherein the lignin bound on the surface of the cellulose nanofibrils possess strong tribonegative properties by acting as an electron-withdrawing component. Specifically, we demonstrated that LCNF nanopaper performed as a highly tribonegative layer in TENGs, outperforming PTFE and conventional petroleum-based plastic tribonegative materials. When LCNF nanopaper was combined as a tribonegative layer with aluminum as a tribopositive one in a zigzag structure to form a cascade type of TENG, it could be used as a power source to run a wireless communication node, which had never been achieved before by any reported TENGs containing a natural material as the tribonegative layer. Our results illustrated the excellent promise of using lignocellulosic materials as green alternatives to fluorine-containing polymers in high power output TENGs for developing green self-powering wireless disposable electronics. We report for the first time a natural wood-derived lignocellulosic nanofibrils (LCNF) tribolayer that could replace fluorine-containing petroleum-based polymers as a tribonegative material for TENGs. The high tribonegativity was due to the presence of natural lignin on the surface of LCNF. The LCNF nanopaper-based TENGs produced significantly higher voltage (~160%) and current (~120%) than TENGs with PTFE as the tribonegative material when paired with various polymeric/metallic tribolayers. Furthermore, assembling LCNF nanopaper tribolayer into a cascade TENG generated an output sufficient for powering a wireless communication node, capable of sending a radio-frequency signal to a smartphone every 3 minutes. This study demonstrates the excellent promises of using LCNF to make high-performance and more environmentally friendly wireless self-powered electronics; and thus pinpoints a new approach for fabricating sustainable triboelectric nanogenerators using natural lignocellulosic materials instead of conventional fluorine-containing petroleum-based polymers as