High sensitivity liquid level sensor for microfluidic applications using a hollow core fiber structure

Liu, Dejun, Li, Wei, Wu, Qiang, Zhao, Haoyu, Ling, Fengzi, Tian, Ke, Shen, Changyu, Han, Wei, Wei, Fangfang, Farrell, Gerald, Semenova, Yuliya and Wang, Pengfei (2021) High sensitivity liquid level sensor for microfluidic applications using a hollow core fiber structure. Sensors and Actuators A: Physical, 332. p. 113134. ISSN 0924-4247

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Official URL: https://doi.org/10.1016/j.sna.2021.113134


Liquid level measurement in microfluidics is challenging, where a sensor with ultra-high sensitivity but miniature in nature is demanded. In this paper, we propose for the first time a microsized fiber sensor structure in both diameter and length for microfluidics applications, which is capable of sub-micrometer scale liquid level measurement. The sensor is simply fabricated by fusion splicing a short section of a hollow core fiber (HCF) between two singlemode fibers (SMFs). HCFs with different air core diameters (10 μm, 20 μm, 30 μm) were investigated and it is found that for a given length of HCF stronger resonant dips were excited in transmission for the HCF with a smaller air core diameter. Thus the HCF structure with an air core diameter of 10 μm (HCF-10) was used for demonstration of high sensitivity liquid level measurement in microfluidics. Simultaneous excitation of both Anti-Resonant Reflecting Optical Waveguide (ARROW) guiding mechanism and Mach-Zehnder interferometer (MZI) in transmission is demonstrated in such an HCF-10 structure when HCF-10 is longer than the critical length. A maximum sensitivity of 0.042dB/µm (corresponding to a calculated liquid level resolution of ~0.23 μm) was experimentally achieved with an HCF-10 length of ~867 μm, which is three times higher than that of the previous reported to date of the most sensitive fiber optic liquid level sensors based on intensity modulation. In addition, the proposed sensor shows good repeatability of measurement and a very low cross sensitivity to changes in the surrounding refractive index.

Item Type: Article
Additional Information: This work was financially supported by the Guangdong Basic and Applied Basic Research Foundation (2019A1515110320); Shenzhen Basic Research Foundation (JCYJ20190808173401660, JCYJ20190808140805488, JCYJ20190808173619062); China Postdoctoral Science Foundation (2019M663025); National Natural Science Foundation of China (11874332); National major scientific research instrument development project of Natural Science Foundation of China (61727816); Department for Agriculture, Food and the Marine, Ireland (17F284).
Uncontrolled Keywords: Fiber sensor, hollow core fiber, antiresonant, Mach-Zehnder interferometer, liquid level
Subjects: H800 Chemical, Process and Energy Engineering
H900 Others in Engineering
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Rachel Branson
Date Deposited: 27 Sep 2021 13:57
Last Modified: 23 Sep 2022 08:00
URI: https://nrl.northumbria.ac.uk/id/eprint/47364

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