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Proceedings Paper

Fast ocean salinity sensing based on long-period fiber gratings integrated with ionic strength-responsive hydrogel (Conference Presentation)
Author(s): Fan Yang; Raman Hlushko; Di Wu; Svetlana Sukhishvili; Henry Du; Fei Tian
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Paper Abstract

Rapid, accurate, and real-time measurements of ocean salinity are of great importance for a host of scientific, commercial and defense applications. We demonstrate a highly sensitive, fast-responding fiber-optic salinity sensor that integrates long-period fiber gratings (LPFG) with ionic strength-responsive hydrogel. Submicron-thick hydrogels were synthesized via layer-by-layer (LbL) assembly of partially quaternized poly(4-vinyl pyridine) (qP4VP) and poly(acrylic acid) (PAA), followed by chemical crosslinking of qP4VP and removal of PAA. Spectroscopic ellipsometry studies of hydrogels with 37% quaternized qP4VP revealed robust and reversible swelling/deswelling behavior of the coatings in solutions with different salt concentrations at pH 7.5. The performance of hydrogel-coated LPFG for the monitoring of sodium chloride solution in the salinity relevant range of 0.4 to 0.8 M was investigated. The swelling/deswelling process induced remarkable changes in the refractive index of the coating, resulting in robust shift in the resonance wavelength of LPFG. The hydrogel-coated LPFG exhibited a sensitivity of 7 nm/M with a response time less than 1 second. There is a linear correlation between the resonance wavelength shift and the salt concentration, making quantification of measured salinity straightforward.

Paper Details

Date Published: 14 May 2018
Proc. SPIE 10654, Fiber Optic Sensors and Applications XV, 106540Q (14 May 2018); doi: 10.1117/12.2304817
Show Author Affiliations
Fan Yang, Stevens Institute of Technology (United States)
Raman Hlushko, Texas A&M Univ. (United States)
Di Wu, Stevens Institute of Technology (United States)
Svetlana Sukhishvili, Texas A&M Univ. (United States)
Henry Du, Stevens Institute of Technology (United States)
Fei Tian, Stevens Institute of Technology (United States)

Published in SPIE Proceedings Vol. 10654:
Fiber Optic Sensors and Applications XV
Alexis Mendez; Christopher S. Baldwin; Henry H. Du, Editor(s)

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