A material made from recycled wood is five times stronger than natural wood and can be made from any timber by-product, including shavings and sawdust.
Orlando Rojas at the University of British Columbia, Canada, and his colleagues have invented a process that dissolves lignin, a glue-like component inside plant cell walls, and exposes cellulose nanofibrils, which are tiny fibres also found in the plant cell wall. The method involves a solvent called dimethylacetamide, used in the presence of lithium chloride.
When two pieces of wood treated in this way are brought together, the nanofibrils bind to create what the researchers call a “healed” piece of wood. Although this no longer looks like natural wood, it has better mechanical properties. Tests show it is more resistant to breaking than stainless steel or titanium alloys.
“We get a mechanical strength that supersedes the strength of the original material,” says Rojas. “It works because we use the inherent properties of cellulose, which is a material that binds together very strongly by something called hydrogen bonding.”
Not only can wood treated this way be re-used to create new objects, but the treatment process can be performed repeatedly on the same pieces of wood to extend their working lifetimes.
“This is a really elegant way to heal wood, using a common cellulose solvent, recovering and enhancing the mechanical properties of nature’s wonder material,” says Steve Eichhorn at the University of Bristol, UK. “The approach is evidently scalable and therein lies the challenge to take this technology to the next level.”
Rojas and his team didn’t examine how much their method would cost if scaled up to an industrial level, but all of the techniques used are well-established. “The processes that we use here are very typical in wood processing,” says Rojas. “So scalability is not an issue.”