A transparent polyurethane coating that heals scratches when heated and simultaneously prevents bacterial growth has been developed by researchers, addressing long-standing challenges in protective surface technology. The material maintains optical clarity comparable to bare glass while demonstrating recyclability and seawater resistance, suggesting applications for phone screens, marine sensors, medical devices, and public-touch surfaces where scratches and microbial contamination are persistent problems.
Polyurethane coatings commonly protect cars, ships, electronics, and public surfaces, but real-world use leads to scratches, fouling, and microbial attachment that gradually cloud transparency and weaken materials. Many existing self-healing films rely on single-use microcapsules or sacrifice transparency or antibacterial capability. Marine environments and medical settings particularly need coatings that resist bacteria without leaching chemicals, yet creating a single material that is transparent, healable, antibacterial, and reprocessable has been difficult because improving one function often compromises another.
A team from Jiangsu University of Technology, Soochow University, and Ghent University reported their solution in the Chinese Journal of Polymer Science on October 11, 2025. They engineered a transparent polyurethane coating strengthened by dynamic selenonium salts that not only repairs scratches under heat but also disrupts bacterial cell membranes. The coating maintained performance after seawater soaking and recycling, indicating practical potential for devices facing daily wear.
The researchers embedded selenonium salts into a polyurethane network using a one-pot synthesis and thermal curing strategy. This dynamic chemistry enabled polymer chains to rearrange under heat, giving the coating vitrimer-like reprocessability while remaining robust at room temperature. When scratched, coatings healed visibly within one hour at 140°C, and with slight pressure, recovery time shortened to approximately 20 minutes. Even after multiple cut-and-remold cycles, the films preserved chemical structure and mechanical behavior.
Antibacterial tests showed selenonium-containing samples dramatically inhibited E. coli and S. aureus growth, with high-loading formulations nearly eliminating colonies. Scanning electron microscope images revealed ruptured bacterial membranes, indicating a contact-killing mechanism. Optical measurements confirmed 90–91% light transmittance, comparable to bare glass, and the coating remained clear after two weeks of simulated seawater immersion with minimal swelling. Pencil hardness reached 1H and adhesion was rated 4B–5B, meeting standards for protective coatings on devices and marine windows.
"This coating behaves like a living surface—it can recover from damage and defend itself against bacteria," the authors explained. "The key lies in the dynamic selenonium chemistry, which allows the polymer network to reorganize during healing while keeping the surface hostile to microbes." They noted that maintaining transparency and mechanical stability after repeated recycling demonstrates the coating's promise in durable and sustainable material design.
The technology could benefit phone screens, touch panels, underwater lenses, public facilities, medical devices, and ship equipment. Its high clarity means it can coat optical components without image loss, while recyclability supports circular material design. With further scale-up, long-term weathering tests, and flexibility tuning, the coating may help reduce maintenance costs and biofouling in marine or healthcare environments, opening the door to next-generation coatings that stay clean, clear, and repairable throughout their lifetime.
