A wooden knife sharper than steel
Researchers at the University of Maryland created a knife made of hardened wood that is almost three times sharper than a stainless steel dinner table knife.
Hardening wood is a process commonly done wth steam and compression, but then the material rebounds somewhat. Cellulose, the main component of wood, has a higher ratio of strength to density than most engineered materials like ceramics, metals, and polymers. However, wood also consists of hemicellulose and lignin, binders for the cellulose, causing wood’s strength to fall short of that of cellulose.
The Maryland team processed the wood in such a way that they removed the weaker components without destroying the cellulose skeleton. First, they partially remove the lignin. Normally, wood is very rigid, but without the lignin, it becomes soft and flexible. Next, the wood is treated with a hot press to density it and remove the water. After that, the material is carved in the desired shape and coated with mineral oil to extend its lifetime. The result is wood that is 23 times harder than the original material.
With the material, the researchers made a knife that cuts through a medium-well done steak easily and can be washed and reused like ceramic and steel knives. In addition, the team demonstrated the material can be used to make nails as sharp as conventional steel ones. Three boards could be hammered together without damaging the nail. The researchers also hope the material can be used to make hardwood flooring resistant to scratches.
The production process of the hardened wood has the potential to be more energy efficient and have a lower environmental impact than the manufacturing of other artificial materials.
Images: Bo Chen