Scalable and Sustainable Approach toward Highly Compressible, Anisotropic, Lamellar Carbon Sponge

Here, we demonstrate that wood can be directly converted into a highly compressible wood carbon sponge (WCS) by lignin and hemicellulose removal followed by carbonization. The significant removal of lignin and hemicellulose via chemical treatment destroys the thin cell walls of natural wood, giving rise to a lamellar structure with numerous stacked arched layers. The lamellar structure can be well preserved even after high-temperature carbonization. Interestingly, such a lamellar structure renders a high compressibility up to 80% and high fatigue resistance of 10,000 compression cycles at 50% strain. Further experimental and modeling studies reveal that WCS can accommodate substantial compression from the bending and flattening of the curved layers, resulting in minimum stretching of individual layers. The WCS also demonstrates a sensitive electrical conductivity change upon compression. Using this lamellar sponged structure and the excellent mechanical and electrical properties of WCS as an example, we demonstrate the great potential of WCS for highly sensitive strain sensors. Lightweight compressible materials enable various applications but are often hindered by limited and unrenewable resources, complex and scale-limited fabrication, and poor mechanical properties. We developed a wood-to-carbon-sponge strategy for fabricating highly lightweight and compressible wood carbon sponge directly from natural balsa wood via a scalable and sustainable top-down approach. The chemical treatment removes lignin and hemicellulose from the wood cell walls, directly converting the lattice-like rigid wood structure into a spring-like compressible lamellar structure. The wood carbon sponge shows outstanding mechanical properties and sensitive electrical responses as a strain sensor. Future applications, including flexible electronics, rechargeable batteries, and catalyst supports, can be expected. Our top-down fabrication strategy opens up new opportunities for developing sponge-like functional materials from sustainable natural resources. A direct wood-to-carbon-sponge transformation is realized via a facile chemical treatment and subsequent carbonization process. Removing the lignin and hemicellulose from balsa wood cell walls is a significant step toward converting the lattice-like wood structure to a spring-like lamellar structure. Magic transformation from brittle wood carbon to compressible wood carbon sponge thus becomes achievable. The wood carbon sponge exhibits a sensitive electrical response as a strain sensor and attractive features for other potential applications.