Radiation dosimeter design based on photonic crystals and other structure color materials

This article reviews recent studies on three-dimensional (3D) radiation dosimeter designs based on photonic crystals and other structure color materials. Photonic crystals and other structure color materials have a wide range of applications in fields such as medical detection, graphic printing, and anti-counterfeiting identification owing to their photonic bandgap properties and bright structural colors. The responsiveness of photonic crystals and other structure color materials to ionizing radiation has been exploited to develop a photonic crystal thin-film dosimeter than can achieve a full visible spectral shift of Bragg absorption peaks under X- or γ-ray irradiation. The dosimeter has a highly tunable application range and a spatial resolution exceeding 30 μm; moreover, it exhibits high environmental stability to light, temperature, and humidity. This study proposes three reading methods: spectrometer detection, naked-eye comparison with standard color cards, and mobile phone-based hue-value detection techniques. Additionally, the sensitivity of the photonic crystal dosimeter was improved by adding polyethylene glycol as a radiation-sensitive material. Gelatin methacrylate was used to prepare hydrogel films, which were chemically modified to introduce unsaturated vinyl groups to achieve sensitive response to X-rays. The hydrogel photonic crystal dosimeter demonstrated favorable dose-response performance on clinical radiotherapy equipment, which agrees well with the measurement results of commercial film dosimeters. Finally, the photonic crystal dosimeter was combined with three-dimensional printing technology to three-dimensionalize the hydrogel photonic crystal dosimeter, thus providing translational potential for topographic dose mapping in clinical radiotherapy. Meanwhile, new thin-film optical interference films have emerged, and the introduction of radiation-responsive groups such as modified double bonds, disulfides/diselenides/disulfides, and azo groups significantly improved their sensitivity and enabled simultaneous drug release under X-ray assistance. This study provides theoretical and technical foundation for the development of portable, real-time, wide-ranging, and high-spatial-resolution photonic crystal radiation dosimeters, which have demonstrated application potential, although their dose verification in actual medical radiotherapy is yet to be realized.