3D Microprinting of Structures with Lanthanide‐Based Fluorophores on Optical Fibers for Multiplexed Sensing

Abstract Femtosecond direct laser writing (fs‐DLW) has revolutionized the fabrication of micro‐optical elements, yet its potential in multiplexed sensing has remained constrained by material limitations and fluorescence crosstalk. Here, a novel platform that integrates lanthanide‐based fluorophores—specifically europium complexes—into commercial fs‐DLW resists (OrmoComp and IP‐Visio) to directly print nano/microstructures on the tips of optical fibers is reported. This strategy exploits the exceptional photostability, narrow emission lines, and long luminescence lifetimes to overcome spectral overlap and photobleaching commonly seen with organic fluorophores. By enabling spectral, temporal, and spatial multiplexing, this approach allows simultaneous detection of distinct biochemical and physical parameters. Five distinct structures are fabricated: two woodpile structures for temperature and redox sensing, a Fabry‐Pérot cavity for refractive index detection, and disc and annular geometries for spatially selective excitation. The results show that combining sub‐micron 3D microfabrication with lanthanide photophysics significantly enhances sensing fidelity, opening new avenues for compact, multi‐analyte fiber‐based diagnostics in biomedical applications.