Researchers from the Department of Mechanical Engineering at the University of Maryland have developed knives out of hardened wood that is three times sharper than those made from stainless steel. To achieve this feat, they processed wood in a special method, which was published in the journal Matter.
While this might seem like an effort as futile as reinventing the wheel, the researchers have good reason to attempt a new development. Conventionally used materials, such as steel and ceramics, are not only made through complex processes but are also energy-intensive. Both these materials need to go through furnaces that reach thousands of degrees burning fossil fuels and adding to the carbon emissions. Therefore a "greener" method is always welcome.
Teng Li, the lead author of the paper, explained that cellulose in wood has a higher strength to density ratio than commercially used materials like ceramic, polymers, and even metals. However, the way we use wood does not allow it to reach its full potential. Apart from cellulose, wood also contains lignin and hemicellulose that perform other functions but weaken the wood when used as a material.
Li and his team, therefore, used a two-step process to strengthen it. In the first step, wood was heated in a chemical bath at 212 Fahrenheit (100 degrees Celsius) that removes the lignin. The wood ended up being very soft and squishy after it was treated under a hot press to remove the water. As a result, the wood was now 23 times harder than regular untreated wood, the researchers claimed.
The treated wood can now be carved into desired shapes and is coated with mineral oil to increase its lifespan. The knife that the researchers made was put through several cycles of washing in the sink and even in the dishwasher but did not give up on its sharpness, the researchers reported.
The team also made nails using the same technique and found their performance comparable to steel ones. They claim to have hammered three wooden boards together with the wooden nails and found that the nails were not harmed at all. What makes this more exciting is that, unlike nails made from steel, the hardened wood nails do not rust. The researchers are also planning to use the method to develop hardwood flooring that is more resistant to wear and tear.
“In our kitchen, we have many wood pieces that we use for a very long time, like a cutting board, chopsticks, or a rolling pin,” Li says. “These knives, too, can be used many times if you resurface them, sharpen them, and perform the same regular upkeep.”
The research shows that there sustainable alternates to many man-made materials if we look hard enough.