Microfluidic in-fiber oxygen sensor derivates from a capillary optical fiber with a ring-shaped waveguide

This article provides a novel all in-fiber gas sensor structure derivates from a specially designed capillary optical fiber (COF) with a ring-shaped waveguide. This optical fiber sensor first realizes sampling from the surface of the optical fiber rather than the fiber ends. The inner surface of waveguide in the COF is coated by oxygen ratiometric luminescence sensitive organosilicone gel films. The light is coupled from the COF ends by fusing it with multimode optical fibers. The laser with the wavelength of 448 nm can be efficiently launched into the COF and guides along the ring-shaped core to excite the dyes. Simultaneously, the gas sample can freely flow through the 7 cm fiber with only 2.0 × 10−4 μL volume and the concentration can be measured by the ratiometric luminescence of the Ru(dpp)3]2+ indicator at 625 nm and the FITC reference dye at 527 nm.