Swiss researchers are tapping into an unexpected energy source right under our feet: wooden floors. Their nanogenerator, which was published in the journal Matter on September 1st, allows the wood to create energy from our footsteps. They also upgraded the wood used in their nanogenerator with a silicone covering and incorporated nanocrystals, resulting in a system that was 80 times more efficient, capable of powering LED lightbulbs and small gadgets.
The researchers started by converting wood into a nanogenerator by sandwiching two pieces of functionalized wood between electrodes. When stepped on, the wood pieces become electrically charged through periodic contacts and separations, similar to a shirt-clinging sock just out of the dryer, a process known as the triboelectric effect. Electrons can move from one thing to another, producing electricity. However, there is one drawback to building a nanogenerator out of wood.
“Wood is largely triboneutral,” says senior author Guido Panzarasa, group leader in the department of Wood Materials Science at ETH Zürich and the Swiss Federal Laboratories for Materials Science and Technology (Empa) Dübendorf. “It indicates that wood has no genuine proclivity to acquire or lose electrons. “This reduces the material’s potential to generate electricity,” thus the problem is to create wood that can attract and shed electrons “Panzarasa elaborates.
To improve the triboelectric characteristics of wood, the researchers covered one-piece with polydimethylsiloxane (PDMS), a silicone that acquires electrons upon contact, while functionalizing the other piece with in-situ-grown nanocrystals known as zeolitic imidazolate framework-8 (ZIF-8). ZIF-8, a hybrid network of metal ions and organic molecules, is more prone to electron loss. They also examined several types of wood to see whether certain species or the manner in which wood is cut could affect its triboelectric capabilities by acting as a better scaffold for the coating.
The researchers discovered that a triboelectric nanogenerator composed of radially cut spruce, common building material in Europe, performed the best. The treatments combined improved the performance of the triboelectric nanogenerator, which generated 80 times more electricity than natural wood. The device’s generation of electricity was also stable under constant stresses for up to 1,500 cycles.
The researchers discovered that a wood floor prototype with a surface area barely smaller than a piece of paper may generate enough energy to power home LED lighting as well as small electronic gadgets like calculators. When a human adult walked on the prototype, it successfully lighted up a lightbulb, converting footfall into electricity.
“Our goal was to show that it was possible to change wood using very environmentally friendly processes to make it triboelectric,” Panzarasa explains. “Spruce is inexpensive and widely available, and it has good mechanical characteristics. The functionalization approach is fairly straightforward, and it is industrially scalable. It’s simply a question of engineering.”
In addition to being efficient, sustainable, and scalable, the newly discovered nanogenerator keeps the characteristics that make wood desirable for interior design, such as mechanical durability and warm colors. According to the researchers, these characteristics could help increase the usage of wood nanogenerators as green energy sources in smart buildings. They also claim that wood building could aid in climate change mitigation by sequestering CO2 from the environment over the material’s lifetime.
The next step for Panzarasa and his colleagues is to further enhance the nanogenerator using more eco-friendly and easier-to-implement chemical coatings. “Even though we first concentrated on basic research, the research that we perform should eventually lead to applications in the actual world,” Panzarasa explains. “The ultimate goal is to comprehend wood’s potentialities beyond those presently known and to enable wood with new qualities for future sustainable smart buildings.”
