City Research Online

Abstract

A novel sensing system based on single mode optical fiber in reflective configuration has been developed to measure the critical meniscus height (CMH) of low volumes of liquids, which is then used to calculate the contact angle. The sensing system has been designed especially for very low volumes of liquids (e.g. bio-liquids) and the work has demonstrated that measurements are possible with a minimum liquid volume of 5 μL . The sensing system is based on monitoring the spectral variation induced by the difference in the refractive index regions surrounding the fiber tip, at the air-liquid or liquid-liquid interfaces. From the experiments performed in water, (by immersing and extracting the fiber sensor in the liquid sample), it can be concluded that the CMH forming on the fiber decreases as the temperature increases. The change of temperature (in this experiment from 22 to 60 °) does not influence the CMH of the sample used in the evaluation (P3 mineral oil), giving an indication of its thermal stability. In addition, a fixed fiber was used to measure the variation in the liquid level when another fiber is immersed in the liquid. The error in the liquid level obtained in the work was small, at 0.34 ± 0.04 %. Such a sensor, allowing accurate measurements with very small quantities is especially useful where liquid sample volumes are limited e.g. biologically sourced liquids or specialized, expensive industrial material in the liquid phase.

Publication Type:	Article
Additional Information:	© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
Publisher Keywords:	Contact angle, critical meniscus height, liquid level variation, meniscus at the interface, optic fiber sensor
Subjects:	T Technology > TJ Mechanical engineering and machinery T Technology > TK Electrical engineering. Electronics Nuclear engineering
Departments:	School of Science & Technology > Engineering
SWORD Depositor:	Symplectic Administrator

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