The IE-TENG system generates electricity through the intrusion and extrusion of liquid in the silicon nanopores. (Image Credit: TU Hamburg, DESY, Künsting)
Engineers at Hamburg University of Technology (TUHH) and other European institutions developed a system that produces electricity from water. The system, called an Intrusion-Extrusion Triboelectric Nanogenerator (IE-TENG), repeatedly applies pressure to push water in and out of nanopores to generate electricity, which occurs at the interface between the solid and the liquid. It also reaches an energy efficiency of up to 9%—the highest ever reported for solid-liquid nanogenerators.
Compared to traditional methods that rely on solid-solid contact, the IE-TENG system utilizes the large internal surface area of the nanopores to greatly enhance contact and increase charge transfer. Instead of using powder, the system employs a monolithic silicon structure for improved efficiency and reproducibility.
During testing, the team discovered that water and an aqueous Polyethylenimine (PEI) solution produced large current and voltage spikes when the liquid was pushed into and out of the pores. By optimizing the conditions using the PEI solution or increasing the compression rate, they achieved a conversion efficiency of about 9%, which is significantly better than earlier solid-liquid systems.
“Even pure water, when confined at the nanoscale, can enable energy conversion,” says Prof. Patrick Huber, spokesperson of the BlueMat – Water-Driven Materials Excellence Cluster at the Hamburg University of Technology (TUHH) and DESY. Dr. Luis Bartolomé (CIC energiGUNE) adds: “Combining nanoporous silicon with water enables an efficient, reproducible power source — without exotic materials, but just by using the most abundant semiconductor on earth, silicon, and the most abundant liquid, water.”
To understand what was happening at the microscopic level, the researchers ran simulations showing how electrons moved between the liquid and the hydrophobic, grafted silicon surface. Their observations indicate that grafting defects help generate a triboelectric charge. Once the liquid intrudes, these defects polarize the surface, causing electrons to flow. When the liquid is extruded, a current flows in the opposite direction.
Due to the p-doped nature of the silicon monolith, the structure works as the triboelectric surface and as the electrode charge collector. Combining these two leads to less energy loss and improved charge transfer compared to systems with separate electrodes.
Don’t expect this system to replace batteries used in phones, laptops, or power-hungry electronics in the future. Although the technology generates electricity, it produces small bursts rather than continuous power. Besides that, it doesn’t store energy and can’t distribute a steady supply like a standard battery.
The team’s work could lead to high-performance, solid-liquid triboelectric energy harvesting systems. They have the potential to power wearables, autonomous devices, or environmental monitors from water or fluid movement. The authors also suggest that refining pore architecture and surface treatment may help enhance performance.
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