Hydrogen-Sensitive Inks with 4D Printing of a Fiber-Tip Hydrogen Microsensor

Optical fiber hydrogen (H 2 ) sensors have garnered attention for avoiding explosion hazards in flammable gas environments. Conventional optical fiber sensors rely on electron beam sputtering and chemical coating for functionalization, but these methods may not achieve precise functionalization of intricate structures. Based on 4D printing principles, an H 2 -sensitive ink containing methacrylate groups modified palladium (Pd) nanoparticles (NPs) is reported, with a printing resolution of 200 nm. Then, a fiber-tip clamped-beam H 2 sensor is fabricated with the femtosecond (Fs) laser-induced two-photon polymerization (TPP) technique. The sensor exhibits compact dimensions and fast responses, only 2.64 s for a 4.0 vol.% H 2 concentration. A high sensitivity of roughly 165 pm % −1 is achieved as the H 2 concentration increases from 0% to 5.5 vol.%. This study demonstrates that H 2 -sensitive microstructures can be flexibly achieved by TPP of H 2 -sensitive inks, offering a solution for achieving on-chip direct laser writing of integrated H 2 microsensors.