Iron-Catalyzed Laser-Induced Graphene—A Novel Approach Towards Green Electronics

Electronic waste (E-waste) is one of the fastest growing waste streams in terms of both volume and environmental impact at a global level. Traditional electronic devices are made of non-renewable and often toxic materials, which can lead to serious environmental contamination upon their disposal. The concept of green electronics focus the development of electronic devices made from renewable and biodegradable materials together with environmentally friendly manufacturing, directly addressing the needs for a future sustainable society.<br/>A promising strategy for producing sustainable electronics is the direct writing of laser-induced graphene (LIG) conductive patterns on biological substrates, especially on wood and wood-based materials. Due to the complex nature of the surface of wood (inhomogeneous structure with variable chemical composition), efficient large-scale manufacturing remains a challenge. Moreover, factors such as high ablation rates, the need of a controlled atmosphere chamber, multiple lasing steps and the use of toxic fire retardants are further limiting the applicability of LIG processes for the production of sustainable electronic devices.<br/>Here, we introduce iron-catalyzed laser-induced graphitization (IC-LIG), an innovative technique that enables to engrave large-scale conductive surfaces on wood. Combining a laser process with a simple surface treatment, this approach overcomes the limitations of conventional LIG processes. We therefore use an aqueous bio-based coating, inspired by the historical iron-gall ink, which smoothens the natural irregularities of the wood surface and protects it from laser ablation and thermal damage while preserving its mechanical properties.<br/>Thanks to our approach, it is possible to engrave highly conductive (up to 2500 S m^-1) carbonaceous patterns even on of thinnest wood veneers and cellulose paper within a single lasing step in ambient atmosphere by simply using a conventional CO₂ laser setup. Thus, we built a touch panel as demonstrator for human-machine interfaces and most durable strain sensors suitable for future structural health monitoring. By further exploiting our IC-LIG approach to treat polydimethylsiloxane (PDMS) thin sheets, we made a first step towards conductive wood composites for future soft electronics applications.