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Here’s what you’ll learn when you read this story:

• Researchers found a way to harness the fundamental properties of triboelectrification, which most people think of it as static electricity, to capture energy.
• By using pressure to repeatedly force water in and out of nanoscale pores, power is continually generated.
• This method could help power future electric cars, wearables, and other electronics.

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Around 600 B.C.E., Thales of Miletus—an Ancient Greek thinker whom some consider to be the world’s first scientist—observed a peculiar effect when he rubbed amber (which in Greek is “elektron”) with fur: light objects became attracted to the material. This phenomenon is what you or I might call static electricity, but it’s actually the result of a phenomenon known as the triboelectric effect.

Because of Thales of Miletus’ interest in this hair-raising curiosity, triboelectrification is one of science’s oldest pursuits—and in a way, Simone Meloni at the University of Ferrara in Italy continues the historical tradition. As a theoretical chemist and condensed matter physicist, Meloni, PhD, has spent years investigating the nanoscale fundamental properties of triboelectrification.

He and his colleagues created a way to generate a practical amount of power from this curious process. In a new study published in the journal Nano Energy, Meloni, along with colleagues from universities and institutions across Europe, described their Intrusion–Extrusion Triboelectric Nanogenerator (TENG) which repeatedly uses pressure to force water in (intruding) and out (extruding) of nanoscale pores.

This work is part of an EU-funded project called “Electro-Fusion,” which aims to create regenerative shock absorbers for electric vehicles. Shock absorbers dissipate 5 to 10 percent of a vehicle’s energy, so developing a shock absorber capable of transforming that consistent rubbing motion into usable energy could boost EV efficiency. TENGs also have potential applications across a variety of technologies, including low-power electronics and wearables.

TENGs work according to the physical process behind the triboelectric effect: when two dielectric materials are brought into contact or rub against each other, they form an electric charge. That’s because the materials exchange either ions, which are electrically charged atoms or molecules, or electrons between them. When they are separated, the materials form a potential difference in electric charge. When electrical conductors—electrodes—are placed behind them and the materials are brought together again, the process ends up generating alternating current, which powers just about everything.

Essentially, it transforms mechanical energy into usable electricity, Meloni explained.

“The amount of [alternating current] generated depends on how much charge the materials can exchange, which in turn is linked to the available surface area,” Meloni said in an email. Per gram, porous materials have “enormous internal surfaces” compared to flat surfaces, he said. “Some have more internal area than a soccer field packed into just one gram of powder.”

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In the study, Meloni and his colleagues reported a 9 percent energy conversion efficiency. The material contains an electrically conductive structure made of porous silicon coated with an extremely thin layer of silica which is modified to be hydrophobic (water-repellent). This modification ensures that the water is eventually expelled from the pores—ensuring the whole extrusion part of the process. The conductive silicon acts as the electrode, which is located only 1 to 2 nanometers away from the triboelectric action itself.

However, it’s the defects in the grafting layer that actually drive triboelectrification, Meloni says.

“Grafted molecules that detach from the silica surface during intrusion and reattach during extrusion—these defects make triboelectrification possible,” he said. “But they also introduce a delicate balance: more defects increase surface charging, yet too many destroy hydrophobicity.”

While our understanding of electricity has evolved vastly over the past two millennia, Meloni said even this current research still holds some mystery.

“Despite centuries of investigation, the fundamental microscopic cause of triboelectrification is still not fully understood,” he said. “Scientists continue to debate what really happens when two surfaces touch, slide, and separate, and whether electrons and/or ions are transferred between them, or something else.”

Meloni described his team’s system as partially optimized and said they’re testing different materials for all three components in their process. While TENGs remain in early development, prototypes for regeneration shock absorbers are already in the works. In other words, a future powered by simple rubbing is already on its way—and the 2,600-year journey to investigate the power of electricity continues.

Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.