Polymer composite fiber-optic Fabry–Perot cavity sensor based on Ti3C2TX MXene enhanced photothermal effect for low-concentration bilirubin detection.

This article focuses on the development of a polymer composite fiber-optic Fabry–Pérot interferometer (FPI) sensor enhanced with Ti₃C₂Tₓ MXene material for the sensitive detection of low-concentration serum bilirubin, a biomarker relevant to chronic diseases such as Alzheimer's disease. The sensor utilizes the photothermal effect of bilirubin under 405 nm laser irradiation, where bilirubin's heat generation causes thermal expansion of the FPI air cavity, shifting the interference spectrum to enable detection. The Ti₃C₂Tₓ MXene coating on polyurethane (PU) enhances bilirubin adsorption and photothermal response, resulting in a sensitivity of 7.51 nm/(μmol/L) and a detection limit of 0.00219 μmol/L within a 1–10 μmol/L range, outperforming previous methods. This approach offers real-time, reagent-free, and selective bilirubin detection with potential applications in early diagnosis and prognosis of chronic diseases.