Highly Elastic and Conductive Lamellar Wood Sponge via Cell Wall Reconfiguration Toward Smart Multifunctional Applications

Three-dimensional porous foams and aerogels with high compressibility and elasticity hold great promise for applications in pressure sensing, electromagnetic interference (EMI) shielding, and thermal insulation. However, their widespread application is often hindered by compromised structural stability and inadequate fatigue resistance under repeated compression. Herein, a sustainable "top-down" cell wall reconfiguration strategy is proposed to fabricate highly elastic, fatigue-resistant, and electrically conductive lamellar wood sponge from natural balsa wood. This strategy involves the conversion of the intrinsic cellular structure of wood into an arch-shaped lamellar architecture reinforced by chemical cross-linking, followed by coating the lamellar scaffold with conductive polypyrrole (PPy) via in situ polymerization. The resulting PPy-coated cross-linked wood sponge (CWS@PPy) demonstrates reversible compressibility, excellent fatigue resistance (∼3.5% plastic deformation after 10,000 cycles at 40% strain). The strain-induced conductivity changes in CWS@PPy enable tunable EMI shielding effectiveness under cyclic compression and also facilities high-sensitivity pressure sensing (0.72 kPa^-1). Additionally, CWS@PPy exhibits a low through-plane thermal conductivity of 0.037 W m^-1 K^-1, which can be dynamically tuned for adaptive thermal management. The proposed mechanically robust and conductive wood sponge provides a versatile and sustainable platform for next-generation smart devices.