Surface-tension-induced force sensing via leakage modulation in anti-resonant hollow-core fiber

In this Letter, we demonstrate a compact all-fiber sensing platform based on an anti-resonant hollow-core fiber (HCF) for deformation-independent measurement of surface-tension-induced forces. Liquid-induced wetting at the cladding-environment interface modifies the optical leakage condition governed by the anti-resonant reflecting optical waveguide (ARROW) mechanism, resulting in measurable transmission modulation. The proposed sensor achieves a sensitivity of 25.47 dB/mN over a force range up to 1.016 mN, with an estimated limit of detection of 3.53 μN. Distinct transmission responses were observed for distilled water, sucrose solution, and saline solution, demonstrating the capability to discriminate liquids with different surface tension characteristics. This approach provides a simple and robust platform for optical force sensing without relying on mechanical deformation.