Dear Zijie Li

To enhance the hydrophilicity of polycarbonate (PC) substrates without using plasma, UV/ozone treatment using 185 and 254 nm wavelengths is an effective alternative. This method works by generating ozone and reactive oxygen species that oxidise the surface, introducing polar groups like hydroxyl and carboxyl, which increase surface energy and improve the adhesion of acrylic coatings. Compared to plasma treatment, UV/ozone is gentler, more cost-effective, and safer for sensitive substrates, although it typically results in less intense surface activation and shallower modification. It effectively lowers the water contact angle (to around 20–40°), but the hydrophilic effect may fade over time. Overall, UV/ozone treatment is a practical choice when moderate surface activation is sufficient, or when plasma equipment is unavailable.