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Nanogenerators enable wooden floors to produce electricity

Image credit: ohio state

A wood-based 'nanogenerator' has been developed that can generate energy from footfalls on wooden flooring.

Swiss researchers used a combination of a silicone coating and embedded nanocrystals to create a device that could power LED lightbulbs and small electronics.

The team began by transforming wood into a nanogenerator by sandwiching two pieces of functionalised wood between electrodes.

The wood pieces become electrically charged through periodic contacts and separations when stepped on, a phenomenon called the triboelectric effect. These electrons can then transfer from one object to another, generating an electrical current.

Typically, wood is a poor material for transporting electrons which limits its ability to generate electricity. “The challenge is making wood that is able to attract and lose electrons,” explained senior author Guido Panzarasa at ETH Zürich.

To achieve this, the team coated one piece of the wood with a silicone that gains electrons upon contact, while imbuing the other piece of wood with nanocrystals that have a higher tendency to lose electrons.

They also tested different types of wood to determine whether certain species or the direction in which wood is cut could influence its electrical properties by serving as a better scaffold for the coating.

The researchers found that radially cut spruce, a common wood for construction in Europe, performed the best and, when treated, generated 80 times more electricity than natural wood. The device’s electricity output was also stable under steady forces for up to 1,500 cycles.

The researchers found that a wood floor prototype with a surface area slightly smaller than a piece of paper can produce enough energy to drive household LED lamps and small electronic devices such as calculators. They successfully lit a lightbulb with the prototype flooring when a human adult walked across it, turning footsteps into electricity.

“Our focus was to demonstrate the possibility of modifying wood with relatively environmentally friendly procedures to make it triboelectric,” Panzarasa said. “Spruce is cheap and available and has favourable mechanical properties. The functionalisation approach is quite simple and it can be scalable on an industrial level. It’s only a matter of engineering.”

The newly developed nanogenerator also preserves the features that make the wood useful for interior design, including its mechanical robustness and warm colours. The researchers say that these features might help promote the use of wood nanogenerators as green energy sources in smart buildings.

They also say that wood construction could help mitigate climate change by sequestering CO2 from the environment throughout the material’s lifespan.

The team now plans to further optimise the nanogenerator with chemical coatings that are more eco-friendly and easier to implement.

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