Microwave Sensing Platform Integrated with Photochromic Films for Ultraviolet Transmission Analysis Through Automotive Glazing

Ultraviolet (UV) radiation passing through automotive glazing presents risks to human health and material longevity, yet its transmission is rarely quantified using electronic sensing methods. This work introduces a microwave resonant sensing platform integrated with UV-responsive photochromic organic thin films for compact, non-optical UV-transmission analysis. The platform employs planar resonators coupled to a coplanar waveguide microwave reader, enabling real-time monitoring of dielectric changes induced by UV-activated molecular switching within slot-die-coated spiropyran/spirooxazine thin films deposited on flexible polycarbonate substrates. When positioned behind glass samples, the hybrid sensor exhibits distinct and repeatable amplitude shifts that correlate with the level of UV radiation reaching the sensing surface. Experimental characterization confirms that the microwave resonator–photochromic film interface provides high sensitivity to UV-induced variations while remaining fully passive and mechanically flexible. The proposed approach offers a low-cost, electronically readable method for assessing UV transmission through glass and supports future integration into embedded monitoring platforms.