Pioneering new process creates versatile moldable wood

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Natural wood has a lower life-cycle cost than most other materials. It is also a lightweight, natural, strong and durable composite material. If its properties and functionality can be improved, it could be an attractive alternative to polymers, metals, and alloys.

Previous methods, such as densification and delignification, were tried but failed to offer the same formability as metals or plastics.

Science was excited to cover the discovery of a new method that can create wood moldable and strong using water shock.

After extracting the lignina, which is a polymer that binds the cells inside wood, and softening it by evaporation, the researchers from the University of Bristol re-swelled it by "shocking it" with water.

"The rapid water-shock process forms an identifiable partially open, wrinkled cell structure that provides space and allows for compression as well the ability to support high strain," stated Professor Liangbig Hu (Director of the Center of Materials Innovation at the University of Maryland).

"The 3D-Molded Wood resulting from this process is six times stronger than the original wood, and comparable to lightweight materials such as aluminum alloys."

The'moldable' wood can then be folded into various shapes, dried and then shaped before being used to make the final product. It is the cell walls of the wood that are wrinkled, which allow for extreme folding without fracturing.

This study was a collaboration between Yale University, Ohio State University and University of Maryland.

Stephen Eichhorn, Professor of Materials and Science Engineering, University of Bristol, was a co-author. He provided some of the mechanistic insight into how wood can deform in this way. Expert on cellulosic material, he has spent over 20 years studying cellulose fibers and wood as well as composites and other plant-based materials.

Professor Eichhorn relates a childhood memory in which his father built his plane from wood.

Professor Eichhorn stated that he bent the wood using steam to make the plane's wings. It is amazing to see that this wood can be made flexible and enhanced with mechanical properties. Who knows, it could even be used in aerospace!

Professor Teng Li of the University of Maryland, co-author, said that moldable wood greatly expands the possibilities for wood as a sustainable material and reduces its environmental impact on buildings and transport applications.

JY Zhu, USDA Forest Products Lab said that "this out-of-the box approach to developing advanced wooden materials will drive wood product innovation as a sustainable way to replace many unsustainable structural materials and combat climate change." It will also help to lower the cost of forest thinning in order to improve forest management and reduce wild, catastrophic forest fires. The U.S. Forest Service Forest Products Laboratory is very excited to work with Professor Hu in this research.

In 2016, Professor Hu established InventWood LLC to market the advanced wood technologies he had developed in his lab.

"The researchers present a clever way to transform the naturally occurring, straightwalled cellular structures in wood into wavy and accordion-like geometries at the microscale," explained Professor John Rogers of Northwestern University. The result is a unique, high-strength wood that can be both flexible and moldable in new ways.

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More information: Shaoliang Xiao et. al. Lightweight, strong and moldable wood via cell-wall engineering as a sustainably structural material, Science (2021). Information from Science Shaoliang Xiao et al. Lightweight, strong and moldable wood via cell-wall engineering as a durable structural material. (2021). DOI: 10.1126/science.abg9556