Ultrafast and Miniature In-Situ Dissolved Gas Sensing Using a Membrane-Free Hydrophobic Hollow-Core Fiber

Conventional in situ dissolved-gas optical sensors predominantly depend on complex gas–liquid separation apparatuses, including gas membrane contactors (GMCs) for gas extraction. However, membrane diffusion is inherently slow, often demanding active vacuum pumping or carrier gas purging that increase system size and power consumption. The membranes also suffer from poor accuracy and thus require routine calibration. Here, we report an ultra-compact, membrane-free sensing architecture based on a hollow-core anti-resonant fiber (HC-ARF) featuring laser-machined microchannels and a hydrophobically modified surface. The sensor achieves an underwater response time of only 10 s via direct liquid–gas interfacial diffusion, which is as quick as dry gas measurements in open air.