Presentation
14 May 2018 Fast ocean salinity sensing based on long-period fiber gratings integrated with ionic strength-responsive hydrogel (Conference Presentation)
Author Affiliations +
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.
Conference Presentation
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Fan Yang, Raman Hlushko, Di Wu, Svetlana Sukhishvili, Henry Du, and Fei Tian "Fast ocean salinity sensing based on long-period fiber gratings integrated with ionic strength-responsive hydrogel (Conference Presentation)", Proc. SPIE 10654, Fiber Optic Sensors and Applications XV, 106540Q (14 May 2018); https://doi.org/10.1117/12.2304817
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KEYWORDS
Fiber optics sensors

Defense and security

Fiber optics

Refractive index

Sensors

Sodium

Spectroscopic ellipsometry

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