Hardened wood as a renewable alternative to steel and plastic

Hard materials are in high demand in engineering applications. Widely used hard materials, e.g., alloys and ceramics, are often nonrenewable and expensive. Their production requires high energy consumption and often leads to negative environmental impacts. We demonstrate a potential low-cost and sustainable hard material made from natural wood. Through a simple and effective approach, bulk natural wood can be processed into a hardened wood (HW) with a 23-fold increase in hardness. To demonstrate the potential applications of HW, we show that an HW table knife can be made nearly three times sharper than commercial table knives. An HW nail can be as functional as a steel nail with comparable performance but is immune from rusting, a key failure mechanism of steel nails. These encouraging applications suggest the promise of HW as a renewable and low-cost alternative for conventional hard materials with the potential to replace plastic table utensils and steel nails.