Fabrication and measurement of fiber optic surface plasmon resonance sensor based on polymer microtip and gold nanoparticles composite

Fiber optic surface plasmon resonance (FO SPR) sensor offers attractive advantages over the conventional prism-based SPR platforms, such as simplicity, cost-effectiveness, and miniaturization. To improve the performance of the existing FO SPR sensor which has been fabricated by depositing a gold thin film on the flat fiber cross-section or side surface, we propose to fabricate the polymer microtip array on optical fiber using simple cost-effective soft and imprint lithography because SPR instruments mainly depend on the structural aspect of the thin metal plasmonic film deposited on the optical fiber substrate. The fabricated microstructures are also combined with the gold nanoparticles to expand the sensing area. The proposed sensor displayed 175% improved sensitivity with linear response according to refractive index changes, when developed FO SPR sensor and conventional FO SPR sensor without microtip array were applied to refractive index measurement, respectively. Based on the obtained results, the proposed FO SPR sensor can ultimately be used in various applications, ranging from food safety, environmental monitoring, and biomarker analysis.