Sustainable wood electronics by iron-catalyzed laser-induced graphitization for large-scale applications.

Ecologically friendly wood electronics will help alleviating the shortcomings of state-of-art cellulose-based "green electronics". Here we introduce iron-catalyzed laser-induced graphitization (IC-LIG) as an innovative approach for engraving large-scale electrically conductive structures on wood with very high quality and efficiency, overcoming the limitations of conventional LIG including high ablation, thermal damages, need for multiple lasing steps, use of fire retardants and inert atmospheres. An aqueous bio-based coating, inspired by historical iron-gall ink, protects wood from laser ablation and thermal damage while promoting efficient graphitization and smoothening substrate irregularities. Large-scale (100 cm 2 ), highly conductive (≥2500 S m -1 ) and homogeneous surface areas are engraved single-step in ambient atmosphere with a conventional CO 2 laser, even on very thin (∼450 µm) wood veneers. We demonstrate the validity of our approach by turning wood into highly durable strain sensors, flexible electrodes, capacitive touch panels and an electroluminescent LIG-based device.