Direct Induction of Porous Graphene from Mechanically Strong and Waterproof Biopaper for On‐Chip Multifunctional Flexible Electronics

Abstract Graphene with a 3D porous structure is directly laser‐induced on lignocellulosic biopaper under ambient conditions and is further explored for multifunctional biomass‐based flexible electronics. The mechanically strong, flexible, and waterproof biopaper is fabricated by surface‐functionalizing cellulose with lignin‐based epoxy acrylate (LBEA). This composite biopaper shows as high as a threefold increase in tensile strength and excellent waterproofing compared with pure cellulose one. Direct laser writing (DLW) rapidly induces porous graphene from the biopaper in a single step. The porous graphene shows an interconnected carbon network, well‐defined graphene domains, and high electrical conductivity (e.g., ≈3 Ω per square), which can be tuned by lignin precursors and loadings as well as lasing conditions. The biopaper in situ embedded with porous graphene is facilely fabricated into flexible electronics for on‐chip and paper‐based applications. The biopaper‐based electronic devices, including the all‐solid‐state planer supercapacitor, electrochemical and strain biosensors, and Joule heater, show great performances. This study demonstrates the facile, versatile, and low‐cost fabrication of multifunctional graphene‐based electronics from lignocellulose‐based biopaper.