In a video from Swiss researchers, someone steps repeatedly on a small square of wood flooring that is wired to a lightbulb, and with every step, the light bulb flickers on. Just by walking on the wood flooring, the person has generated electricity.
This works through something called the triboelectric effect, which is a way to generate electricity by transferring electrons from one material to another, usually because of the way those materials rub together (think static electricity). Though using this effect isn’t completely new—triboelectric nanogenerators have been used before in flooring and even wearable fabric—the researchers, from the Wood Materials Science Laboratory at the ETH Zürich university and the Swiss Federal Laboratories for Materials Science and Technology in Dübendorf, were able to actually make their generator out of wood, using a sustainable material that could become part of smart buildings of the future. The researchers published their work on their nanogenerator in the journal Matter.
Most triboelectric nanogenerators use synthetic materials— like teflon or silicone—to conduct their electricity; these are called “triboactive” materials. Wood isn’t a great material for this because it’s basically neutral—it neither attracts nor loses electrons. A triboelectric nanogenerator needs to use one material that does each, in order to generate a charge. To get around this, the researchers changed the wood’s triboelectric properties, coating one piece with a silicone and the other with nanocrystals called ZIF-8, which includes metal ions and organic molecules.