Spray-Coated Self-Stratifying Fibers Supercharge Triboelectric Nanogenerators

Triboelectric nanogenerators, or TENGs, have long promised a world where everyday motion—footsteps, keystrokes, the tap of a finger—can be converted directly into usable electricity. The physics is elegantly simple: when two dissimilar materials touch and then separate, electrons shuffle between them, generating a voltage that can drive tiny sensors or harvest ambient mechanical energy. The engineering, however, has been far less simple. The best-performing triboelectric layers typically rely on intricate fibrous architectures that maximize contact area and charge trapping, but those fibers are usually made by electrospinning, a technique that demands high-voltage power supplies, controlled humidity chambers, and slow, batch-by-batch processing. That bottleneck has kept fiber-based TENGs largely confined to laboratory benches rather than factory floors. Now, a team of researchers in South Korea reports a way to sidestep the problem entirely, using nothing more exotic than a spray gun and the physics of phase separation.

Writing in the journal Advanced Composites and Hybrid Materials, Insun Woo, Chaelin Park, and their colleagues at the Korea University of Technology and Education and the Korea Research Institute of Chemical Technology describe a one-step spray-coating strategy that simultaneously forms fibers, builds hierarchical micro- and nanostructures, and drives spontaneous phase separation within the coating. The key insight is that rapid solvent evaporation during spraying can do the work that high-voltage electric fields normally perform. As the atomized droplets of a blended polymer solution hit the substrate and the solvent flashes away, the two polymers in the mixture—silicone-based polydimethylsiloxane, or PDMS, and the ferroelectric copolymer poly(vinylidene fluoride-co-trifluoroethylene), abbreviated P(VDF-TrFE)—demix on their own according to their surface energies. The result is a self-stratified hybrid fibrous composite, assembled in a single pass without any high-voltage equipment at all.

The stratification is not a random accident but a compositionally graded architecture with a deliberate logic to it. PDMS, with its low surface energy and famously hydrophobic, electron-donating character, migrates to the exterior of the fibrous network, forming an enriched sheath at the outer surface. P(VDF-TrFE), a fluorinated copolymer prized for its high dielectric constant and strong charge-trapping ability, concentrates in the interior of the fibers. This spontaneous sorting matters because the two polymers play complementary roles in a triboelectric device. The outer PDMS-rich layer is the material that actually touches and separates from the counterface during operation, so its strong tribopositive character boosts charge transfer at the interface. The inner P(VDF-TrFE)-rich core, meanwhile, acts as a high-capacity reservoir that stabilizes and retains the generated charge, preventing the losses that normally erode output over time.

One of the most technically significant consequences of this self-stratification is its effect on the crystalline structure of the fluoropolymer. P(VDF-TrFE) can crystallize in several polymorphic phases, but the one that matters for electromechanical and dielectric performance is the β-phase, in which the fluorine and hydrogen atoms on the polymer backbone are arranged to give each chain a permanent dipole moment. The researchers found that the fibrous, PDMS-templated environment promotes β-phase crystallization within the P(VDF-TrFE)-rich interior, effectively polarizing the core of the material without the need for corona poling or other post-treatments in the way many conventional composites require. Combined with the enlarged effective contact area provided by the hierarchical fiber morphology, the graded structure delivers synergistic gains: more charge is generated at the surface, more charge is retained in the bulk, and more of that charge is converted into useful electrical output.

The numbers reported for the optimized device are impressive for a spray-coated architecture. The triboelectric nanogenerator produces an open-circuit voltage of 290 volts and a short-circuit current of 7.5 microamperes, with a maximum power density of 1.23 watts per square meter. For context, these output figures place the spray-coated composite in the same performance territory as fiber-based TENGs fabricated by electrospinning, but from a process that is inherently compatible with roll-to-roll coating, large-area deposition, and low-cost manufacturing. The fibrous network’s large surface area and mechanical flexibility—qualities that have made electrospun mats attractive in the first place—are preserved, while the fabrication barrier that has limited scalability is removed.

Durability is where many triboelectric devices stumble, since repeated contact and separation cycles can wear surfaces, degrade interfaces, and bleed away stored charge. The Korean team subjected their devices to extended endurance testing and found that the output remained stable over 30,000 mechanical cycles. That robustness is attributed in large part to the PDMS-enriched sheath, which is both mechanically resilient and chemically inert, shielding the underlying ferroelectric core while maintaining a consistent contact surface. Stable long-term output is a prerequisite for any practical deployment, whether the device is embedded in a wearable, laminated onto a floor, or integrated into an interactive surface that will be touched thousands of times a day.

What elevates the work from a materials demonstration to a systems-level advance is the pair of working applications the researchers built with their coatings. In one, a TENG-based sensor array was used for handwritten letter recognition: as a stylus or finger traces characters across the spray-coated surface, the pattern of electrical pulses generated by contact and separation encodes the writing dynamics, allowing the letters to be identified from the signal alone. In the other, the same class of device was integrated into a smart door lock, where the mechanical act of touching or interacting with the lock generates the electrical signal that operates it. Both demonstrations point toward self-powered sensing systems—interfaces that harvest the energy of the interaction they are measuring, eliminating batteries and wiring for low-power applications.

The broader implications reach into several fast-growing fields. Human–machine interfaces, from touch-sensitive prosthetics to gesture-recognition surfaces, need sensors that are flexible, durable, and cheap to produce at scale; a spray-coatable triboelectric layer checks all three boxes. Large-area energy harvesting—converting the mechanical energy of wind, rain, foot traffic, or vibration into electricity—has been limited by the cost and throughput of nanofabrication, and a one-step spray process could change the economics of covering square meters rather than square centimeters. And because the self-stratification mechanism is driven by fundamental thermodynamics—surface energy differences and solvent evaporation rates—the same principle could plausibly be extended to other polymer pairs, opening a design space of graded fibrous composites tailored for specific electronic functions.

The study, published open access on 5 September 2026 and citable under DOI 10.1007/s42114-026-02068-z, was supported by the National Research Foundation of Korea, the BK-21 FOUR program, the Korea Research Institute of Chemical Technology Core Research Program, and the Korea Planning and Evaluation Institute of Industrial Technology. The authors, including corresponding researchers Jin Woo Bae, Ju Hyeon Kim, and Eun-Ho Sohn, declare no competing interests. As with any early-stage materials research, questions of long-term environmental stability, manufacturability at true industrial scale, and integration with power-management electronics remain to be fully resolved. But the central achievement stands on its own: a fibrous, hierarchically structured, compositionally graded triboelectric material made in one step, with a spray gun, no high voltage, and performance that rivals the laboratory gold standard. Sometimes the most elegant solution to a fabrication bottleneck is to let physics do the assembly.

Subject of Research: One-step spray-coated self-stratified PDMS/P(VDF-TrFE) hybrid fibrous composites for triboelectric nanogenerators

Article Title: One‑step spray‑coated self-stratified PDMS/P(VDF‑TrFE) hybrid fibrous composite-based Triboelectric Nanogenerators

Article References: Woo, I., Park, C., Jo, B. E., Yoon, J.-M., Kim, D. H., Bae, J. W., Kim, J. H., & Sohn, E.-H. (2026). One‑step spray‑coated self-stratified PDMS/P(VDF‑TrFE) hybrid fibrous composite-based Triboelectric Nanogenerators. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02068-z

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02068-z

Keywords: triboelectric nanogenerator, spray coating, self-stratification, PDMS, P(VDF-TrFE), fibrous composites, phase separation, energy harvesting, self-powered sensors, human-machine interfaces, beta-phase crystallization, hybrid materials