Direct Writing of Conductive Polymer Circuits on Wood via Spatially Confined Synthesis for Sustainable Human–Computer Interaction

Fabricating high-resolution conductive circuits on natural wood remains challenging due to its porous, anisotropic structure, which causes uncontrolled reagent diffusion and poor pattern fidelity. SophWood, a spatially confined in-situ polymerization strategy, selectively deposits polypyrrole (PPy) within laser-defined regions of wood, achieving a minimum trace width of 0.4 mm. A hard wood wax oil coating serves as the hydrophobic barrier, and laser-ablated microchannels define the polymerization template. The orthogonal experiment identified FeCl3 concentration as the dominant factor (61.32% of conductivity variance), yielding a maximum conductivity of 1.56 × 10−³ S·m−1. SophWood demonstrated superior adhesion durability (2.1% resistance increase after ASTM D3359 versus 16.5–100% for reference) and multi-modal sensing (humidity: ΔR = 3.4 kΩ; temperature: ΔR = 6.5 kΩ). Geometric resistance tunability (7.25–39 MΩ), species versatility, and accessibility were validated through prototypes and a user study. SophWood offers the HCI community a replicable, sustainable framework for embedding interactive functionality into natural wood.