Flexible radiochromic films based on 10.12-pentacosadiynoic acid-doped ionogel enabling 2D real time dosimetry

In this work, we report the development and characterization of a new flexible radiochromic film based on 10.12-pentacosadiynoic acid (10.12-PCDA) embedded in an ionogel (IG) matrix. Designed for real-time, in-situ 2D dosimetry, the film integrates all components within a single, flexible layer. This enhances its adaptability to curved and irregular surfaces and facilitates adjustment to patient morphology. The ionogels were produced by immobilizing the ionic liquid 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (BMIM TFSI) within a polymeric matrix of Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP), achieving thin (100 μm) and flexible (Young's modulus of 4 MPa) films. Ionogels were doped with the radiochromic molecule 10.12-PCDA, achieving a maximum concentration of 8.2 wt% in the film, which confers it with high sensitivity to radiation. Dose response calibration was performed with a 90 kV microfocus X-ray source and revealed a strong correlation between changes in the optical density of the films irradiated and radiation dose, with the most sensitive formulation (8.2 wt% 10.12-PCDA, IL/polymer ratio 3:1) displaying a detection limit of 0.25 Gy. The radiochromic properties of these films, combined with a customised opto-mechanical setup and open-source colour analysis software, enable a system for 2D and real-time dosimetry with a spatial resolution of 1 mm. The films demonstrated excellent flexibility, mechanical stability post-irradiation, and reliable dose distribution assessment on curved surfaces (90-180° curvature angle). These results position 10.12-PCDA@IG films as promising candidates for in vivo dosimetry on the patient skin.