The Photonics Group in the Department of Physics and Physical Oceanography of the Memorial University of Newfoundland in Canada has just reported a new technique that can achieve simultaneous measurement of soluble analytes and temperature (P. Lu, L. Men, and Q. Chen, IEEE Sensors J. 9 (2009) 340).

Monitoring of physical, chemical, and biological parameters in water is of great importance for environmental conservation, food industries, and biomedical applications, in which versatile sensors are highly demanded to achieve simultaneous measurement of temperature and different chemical parameters, for example, concentrations of water-soluble analytes including sugar, metal ions, metal compounds, and chemical traces. 

The new technique utilizes two fiber Bragg gratings (FBGs) of different polymer coatings (polyimide and acrylate) to achieve simultaneous measurement of temperature and concentrations of water-soluble analytes such as sugar and potassium chloride. Polyimide polymers are hygroscopic and swell in aqueous media as the water molecules migrate into them. In order to achieve simultaneous measurement of temperature and concentrations of water-soluble analytes, an acrylate-coated FBG functions as a temperature sensor which is not sensitive to sugar or KCl concentration, while a polyimide-coated FBG is sensitive to sugar or KCl concentration and acts as a chemical sensor. The experimental results indicate that other water-soluble analytes can be detected by this sensor system as well. The experimental results showed that the temperature sensitivity of the acrylate-coated FBG, temperature, sugar, and KCl concentration sensitivities of the polyimide-coated FBG are 0.0102 nm/oC, 0.0094 nm/oC, 0.0012 nm/oBx, and 0.0126 nm/M, respectively. As long as the soluble analytes swell the polyimide coating, different responses from the grating (sensitivity, rate, etc.) are expected, which enables the possibility to differentiate and quantify different analytes. In practice, through extensive experimentation and accumulation of data, a calibration curve for different substances can be developed before routine uses. The fiber optic sensor reported is a versatile chemical sensor to monitor different soluble analytes. Since the two sensing elements have been integrated on one standard single-mode telecommunication fiber, it is possible to achieve quasi-distributed real-time monitoring of temperature and analytes over a long distance.

For more information, please contact:

Qiying Chen

qiyingc@mun.ca  

Tel: 709-737-8878

Fax: 709-737-8739

Department of Physics and Physical Oceanography

Memorial University of Newfoundland

St. John's, NL A1B 3X7 Canada

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