Highly smooth, robust, degradable and cost-effective modified lignin-nanocellulose green composite substrates for flexible and green electronics

Cellulose-based substrates have emerged as strong candidates for flexible and green electronics to impede e-waste generation and fulfill device functions. However, current cellulose-related substrates are incapable to ensure both high performance and low-cost requirements. Here, we developed high-performance, low-cost, and eco-friendly green composite substrates for flexible and green electronics. The green composite substrates were constructed by two natural components of lignin and nanocellulose derived from wood. Through pretreatments of dialysis fraction and epoxidation modification, lignin's heterogeneous structure and moderate surface activity were remarkably improved. The two components exhibit excellent compatibility, and the regenerated substrates demonstrate plastic-like high performance and paper-like degradability, showing low surface roughness (4.68 nm), high ultimate tensile stress (146 MPa) and elastic modulus (16.16 GPa), high transmittance (59.57%@750 nm), and prominent thermal, electrical stability and flame retardancy. After lignin pretreatments, the ultimate tensile stress was vastly increased by 554%. And modified lignin can be added with an ultra-high loading amount (up to 50 wt%), which significantly reduces substrate cost. Consequently, RFID antennas were fabricated on these substrates, which demonstrate distinctive degradability. This study provides a sustainable approach to utilize lignin and cellulose to produce value-added green composites. This work presents a promising route for traditional electronics to replace non-degradable plastics to head towards flexible and green electronics to reduce e-waste generation.