By cycling water in and out of nanoscale pores under pressure, the researchers have created a method that continuously transforms mechanical movement into usable electric power. This breakthrough could lead to energy-harvesting shock absorbers in electric vehicles and low-power electronics.
The system, led by Simone Meloni, a theoretical chemist and condensed matter physicist at the University of Ferrara in Italy, reimagines static electricity as a renewable resource. Meloni’s work forms part of Electro-Fusion, an EU-funded project aiming to turn lost mechanical energy—like the constant movement in vehicle suspension systems—into electricity. The researchers published their findings in the scientific journal Nano Energy.
The innovation centers around a device called an Intrusion–Extrusion Triboelectric Nanogenerator (TENG). This small-scale generator leverages water pressure to produce an alternating current by repeatedly forcing water into (intrusion) and out of (extrusion) a porous material. The friction between materials—long associated with triboelectric effects—becomes a consistent power source, thanks to careful engineering at the molecular level.
From Ancient Amber to Silicon Pores
The concept of triboelectrification is not new. It dates back to 600 BCE, when Thales of Miletus observed that rubbing amber (elektron in Greek) with fur caused it to attract light objects. While modern science now understands this as the build-up of electrical charge from contact and separation of materials, the microscopic origins of the effect remain unclear, even today.
Meloni’s team brings this ancient curiosity into modern labs. Their TENG device is built using porous silicon coated with a thin silica layer, which is treated to be hydrophobic—that is, it repels water. This feature ensures the water gets expelled during each extrusion phase, maintaining the repetitive action needed to generate energy.
Behind the triboelectric materials, an electrically conductive electrode is placed just 1 to 2 nanometers away, allowing the captured electric charge to be converted into alternating current—the same type of current used to power most electronics.
Surface Area, Not Size, Drives Efficiency
According to Meloni, the strength of the TENG lies in its use of porous materials, which contain massive internal surface areas despite their small size. “Some have more internal area than a soccer field packed into just one gram of powder,” he explained. This high surface area enables greater charge exchange between materials during the intrusion and extrusion cycles.
As the water enters the pores, the friction from its movement and interaction with the surface creates an electric charge. The system reported an energy conversion efficiency of 9 percent, a promising figure considering the scale and simplicity of the technology. The motion doesn’t need to be large or forceful—it just needs to be repetitive, making it ideal for harvesting power from everyday mechanical actions, such as a car hitting a bump or a person walking.
The Role of Controlled Imperfections
An unexpected factor in the device’s performance is the presence of defects in the silica layer. These imperfections, according to Meloni, are not flaws but features that enable the triboelectric reaction. During water intrusion, grafted molecules detach from the surface, and during extrusion, they reattach—a cycle that drives the generation of charge.
Still, the process walks a fine line. “More defects increase surface charging,” Meloni said, “yet too many destroy hydrophobicity.” Maintaining the right balance is key to keeping the system functional while maximizing its energy output.
Though Meloni described the current setup as “partially optimized”, his team is already experimenting with alternative materials for all three components of the device. The aim is to improve durability and performance without sacrificing efficiency.
Tapping Energy From Everyday Motion
One of the most immediate applications under development is in regenerative shock absorbers for electric vehicles. According to Popular Mechanics, 5 to 10 percent of a vehicle’s energy is lost through shock absorption. Embedding a TENG into these systems could capture that constant motion and transform it into energy that feeds back into the vehicle.
Beyond automotive uses, the technology also holds promise for wearable electronics and low-power devices, where subtle, continuous movements—like a wrist swinging or shoes striking the ground—could serve as an untapped energy source. Unlike solar panels or traditional batteries, these devices wouldn’t rely on external conditions or charging infrastructure.
Still, the fundamental science is far from settled. As Meloni pointed out, despite centuries of research, scientists still debate what actually happens when two surfaces touch, slide, and separate—and whether ions, electrons, or another mechanism is responsible for the electric charge.