The race for developing “smart” technology for our everyday items has been ongoing for decades now, with ideas going as far back as when we first envisioned the beginnings of our technology-powered world. One of the biggest ideas of the past few decades was the concept of a “smart home,” in which inhabitants need only shout or do certain actions for the house to respond to their needs; think lights that turn on or off when you clap your hands, or garage doors that open by themselves whenever your car leaves or enters the driveway.
Part of the chase for this dream is the constant stream of development into domestic electronics; it seems that nowadays, it’s no longer enough for our house implements to do one thing, and one thing alone. While technologies like these are at their infancy, certain applications of them already do exist. An example of this is the famous “power mat,” installed in Shibuya station in Tokyo, Japan, back in 2008. As commuters stepped on the mats, scattered outside the station, they provided power to a nearby holiday light display.
While these human-powered implements seem a novelty at first, there is a real pursuit of utilizing these technologies—or a version of them, at least—back in the home. However, certain considerations must be taken into account before hastily bringing them to your next house design. Aesthetics and functionality are also part of the equation; after all, there’s not much use placing special powering tiles inside your home when it means replacing your floorings with plastic contraptions. Luckily for us, researchers from ETH Zürich seem to be on the pursuit of both form and function in their new feat, published in the journal Matter. In it, they developed “functionalized” wood that can power a small lightbulb with footsteps.
The basic design of their study involves two wooden veneers, with electrodes layered beneath the two. When stepped on, the two layers of wood come into contact with each other, then separate; this action creates the flow of electrons facilitated by the electrode underneath. The technology takes advantage of what is known as the triboelectric effect, where a material becomes electrically charged when mechanically separated from another after making direct contact due to the materials having “loose” electrons; an everyday manifestation of this is what we call static electricity, like when packing peanuts stick to the fur of your cat. The two layers were sandwiched into implements they termed triboelectric nanogenerators (TENGs).
Of course, we don’t readily observe materials sticking directly to wood with static electricity; wood by itself is considered essentially triboneutral, meaning it “has no real tendency to acquire or to lose electrons,” according to Guido Panzarasa, lead author of the study. According to Panzarasa, the challenge for the team was to create wood with the ability to gain and lose electrons, much like packing peanuts or balloons after coming into contact with your hair.
The solution they found for their predicament involved functionalizing their wood samples, where they use physical or chemical processes to impart their desired properties on it that it otherwise wouldn’t have or manifest. Here, the lower wood veneer was coated with poly(dimethylsiloxane) (PDMS), a silicone material that’s also used in silicone gel-based breast implants. The upper layer, on the other hand, was embedded with zeolitic imidazole framework-8 (ZIF-8), a material dotted with metal ions like copper and iron. PDMS readily accepts electrons, while ZIF-8 readily loses it. This created the flow of electrons that powered the circuit.
The team also found that radially-cut spruce wood was the most effective for the technology. Finally, they tested their new technology by applying it to flooring that’s roughly the size of a piece of A4 paper. In this setup, the TENGs were able to power everyday electronics like household LED lamps and other small electronics. The treated wood generated electricity 80 times more efficiently compared to what wood was capable of doing naturally; it was also able to function for up to 1,500 cycles while under steady stress.
Panzarasa mentioned that one of their team’s primary goals was to develop a method of functionalizing wood for this function that was “environmentally friendly,” The lead author also added that the procedure for this was simple, meaning it was “industrially scalable.” Future work for the team includes refining the wood treatment process to make it even more eco-friendly and easier to apply. Conveniently, the technology maintained the general strength and appearance of natural wood, meaning it doesn’t detract from certain home style sensibilities if used in one.
Said Panzarasa: “The ultimate goal is to understand the potentialities of wood beyond those already known and to enable wood with new properties for future sustainable smart buildings.”\
Bibliography
- Fermoso, J. (2008, December 17). Power Generating Floor in Train Stations Light Up Holiday Displays. WIRED. Retrieved September 16, 2021, from https://www.wired.com/2008/12/power-generatin/
- Lavars, N. (2021, September 1). Nanogenerator wooden flooring powers lightbulbs with footsteps. New Atlas. Retrieved September 16, 2021, from https://newatlas.com/energy/nanogenerator-wooden-flooring-powers-electronics-footsteps/
- Sun, J., Tu, K., Büchele, S., Koch, S. M., Ding, Y., Ramakrishna, S. N., Stucki, S., Guo, H., Wu, C., Keplinger, T., Pérez-Ramírez, J., Burgert, I., & Panzarasa, G. (2021). Functionalized wood with tunable tribopolarity for efficient triboelectric nanogenerators. Matter, 4(9), 3049–3066. https://doi.org/10.1016/j.matt.2021.07.022
