Humidity usually kills static electricity – but not in every case. In dry air, a charged surface can hold energy for minutes. Add moisture, and that charge disappears almost instantly, as thin layers of water form and quietly conduct it away. This basic property of water has long limited the performance of triboelectric nanogenerators, or TENGs.
These devices generate electricity when two different materials come into contact and then separate, briefly exchanging charge. They have been widely seen as a potential power source for wearable sensors and implantable medical devices.
However, their efficiency typically drops sharply once humidity rises above 60–70 percent – a serious constraint, given that the human body and many real-world environments regularly exceed those levels.
Rethinking humidity by turning water into a power source
For years, researchers have tried to shield TENGs from moisture by making their surfaces water-repellent or sealing them inside protective casings. While effective to a point, these fixes add design complexity and struggle to scale across the intricate 3D structures demanded by modern wearable and implantable devices, Nanowerk reports.
A newer strategy takes the opposite direction: instead of resisting water, it embraces it. By engineering the tribolayer to be strongly hydrophilic, captured moisture can actively support charge generation rather than dissipate it. The challenge has been translating this concept into a material that is both printable and capable of delivering consistent, high performance.
A new study in Advanced Functional Materials introduces a material designed to work with humidity rather than against it. The researchers developed a photocurable resin that can be shaped using LCD 3D printing into fine, complex structures.
What sets it apart is its chemistry: the polymer network is packed with polar groups that attract and hold water molecules. Instead of degrading performance, this built-in moisture absorption enhances it. As humidity increases, the resulting films generate stronger output, turning a long-standing limitation of triboelectric nanogenerators into a functional advantage.
Charged polymers help nanogenerators thrive in high humidity
Instead of testing a single material, the researchers compared three acrylic polymers, each crosslinked with polyethylene glycol diacrylate and formed into thin films about 200 micrometers thick. These materials include chemical groups (carboxyl, hydroxyl, and amide) that readily bond with water in the air. Among them, the amide-based version stood out, delivering the strongest performance, with output continuing to rise even as humidity reached 90 percent.
The team then pushed the concept further. They introduced a zwitterionic component, sulfobetaine methacrylate, which contains both positive and negative charges within the same molecule. This structure enhances polarization and draws in even more water, strengthening the material’s ability to generate electricity under humid conditions.
The best performance came at 5 wt%, where the device reached 45.6 microamperes, 802 volts, and 48.4 W/m² at 90% humidity – about twice the power of earlier designs, without inorganic fillers and still fully printable. At 10%, performance dropped as excess ions formed clusters, increasing conductivity and causing charge leakage. The key is balancing polarization gains against these losses.
Furthemore, simulations showed that water binds tightly to the polymer, boosting dipole strength, while Raman spectroscopy confirmed that water remains structured rather than forming conductive films, allowing output to rise with humidity.