Development of solid-state fluorescence lifetime standards for clinical applications using dyed epoxy resins.

Significance: Fluorescence lifetime imaging (FLIm) offers label-free contrast based on intrinsic tissue properties, making it a promising tool for clinical diagnostics and intraoperative guidance. However, the lack of robust, reproducible standards for system validation limits cross-platform comparability, impedes quality assurance, and hinders clinical translation. Aim: We aim to develop and characterize a set of stable solid-state fluorescence lifetime (FLT) standards using dyed epoxy resins, with the goal of enabling reliable calibration, benchmarking, and validation of FLIm systems in both research and clinical environments. Approach: A series of solid standards incorporating different dyes were fabricated to span a range of lifetimes from sub-nanosecond to over 3.5 ns. These materials were evaluated for FLT, emission intensity, photostability under UV exposure, and fabrication repeatability. The influence of dye concentration and microstructural uniformity was assessed using a confocal microscope. The standards were also applied to validate a chip-on-tip FLIm micro-camera designed for endoscopic imaging. Results: The dyed epoxy standards demonstrated consistent and reproducible lifetimes, good photostability, and scalable fabrication. Confocal imaging revealed some microstructural heterogeneity, whereas bulk measurements remained robust. The standards enabled effective validation of the FLIm micro-camera, including spatial and temporal resolution assessment, and highlighted platform-dependent biases in lifetime estimation. Conclusions: Dyed epoxy materials show strong potential as practical, scalable tools for FLIm system calibration and quality assurance. These standards may support cross-platform validation and benchmarking of emerging FLIm technologies and could contribute to the development of future regulatory frameworks for clinical adoption.