A wood-based ‘nano generator’ has been developed that can generate energy from footsteps on wooden floors.
Swiss researchers used a combination of a silicone coating and embedded nanocrystals to create a device that can power LED lights and small electronics.
The team started by transforming wood into a nanogenerator by placing two pieces of functionalized wood between electrodes.
The pieces of wood are electrically charged by periodic contacts and separations when stepped on, a phenomenon called the triboelectric effect. These electrons can then be transferred from one object to another and generate an electric current.
In general, wood is a poor material for transporting electrons, which limits its ability to generate electricity. “The challenge is to make wood that can attract and lose electrons,” explains senior author Guido Panzarasa of ETH Zurich.
To achieve this, the team coated one piece of wood with silicone that gains electrons on contact, while the other piece of wood is infused with nanocrystals that have a greater tendency to lose electrons.
They also tested different woods to determine whether certain woods or the direction in which wood is cut can affect its electrical properties by serving as a better scaffold for the coating.
The researchers found that radially cut spruce, a common construction wood in Europe, performed the best and, when treated, generated 80 times more electricity than natural wood. The electricity output of the device was also stable under constant forces for up to 1500 cycles.
The researchers found that a wooden floor prototype with an area slightly smaller than a piece of paper could produce enough energy to power household LED lights and small electronic devices such as calculators. They successfully lit a light bulb with the prototype floor when a human adult walked over it and turned footsteps into electricity.
“Our focus was to demonstrate the possibility of modifying wood with relatively environmentally friendly procedures to make it triboelectric,” Panzarasa said. “Firing is cheap and available and has favorable mechanical properties. The functionalization approach is quite simple and can be scalable on an industrial level. It’s just a matter of technique.”
The newly developed nanogenerator also retains the properties that make the wood useful for interior design, including mechanical robustness and warm colors. The researchers say these features could help promote the use of wood nanogenerators as green energy sources in smart buildings.
They also say wood construction can help mitigate climate change by storing CO2 from the environment over the life of the material.
The team now plans to further optimize the nanogenerator with chemical coatings that are more environmentally friendly and easier to implement.