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Ratiometric Optical Temperature Sensor Using Two Fluorescent Dyes Dissolved in an Ionic Liquid Encapsulated by Parylene Film
Department of Mechano-Informatics, Graduate School of Information Science and Technology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-8656 Tokyo, Japan
IRT Research Initiative, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-8656 Tokyo, Japan
* Author to whom correspondence should be addressed.
Received: 16 February 2013; in revised form: 21 March 2013 / Accepted: 24 March 2013 / Published: 27 March 2013
Abstract: A temperature sensor that uses temperature-sensitive fluorescent dyes is developed. The droplet sensor has a diameter of 40 µm and uses 1 g/L of Rhodamine B (RhB) and 0.5 g/L of Rhodamine 110 (Rh110), which are fluorescent dyes that are dissolved in an ionic liquid (1-ethyl-3-methylimidazolium ethyl sulfate) to function as temperature indicators. This ionic liquid is encapsulated using vacuum Parylene film deposition (which is known as the Parylene-on-liquid-deposition (PoLD) method). The droplet is sealed by the chemically stable and impermeable Parylene film, which prevents the dye from interacting with the molecules in the solution and keeps the volume and concentration of the fluorescent material fixed. The two fluorescent dyes enable the temperature to be measured ratiometrically such that the droplet sensor can be used in various applications, such as the wireless temperature measurement of microregions. The sensor can measure the temperature of such microregions with an accuracy of 1.9 °C, a precision of 3.7 °C, and a fluorescence intensity change sensitivity of 1.0%/K. The sensor can measure temperatures at different sensor depths in water, ranging from 0 to 850 µm. The droplet sensor is fabricated using microelectromechanical system (MEMS) technology and is highly applicable to lab-on-a-chip devices.
Keywords: temperature sensor; ionic liquid; fluorescent dye; Parylene on liquid deposition (PoLD)
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MDPI and ACS Style
Kan, T.; Aoki, H.; Binh-Khiem, N.; Matsumoto, K.; Shimoyama, I. Ratiometric Optical Temperature Sensor Using Two Fluorescent Dyes Dissolved in an Ionic Liquid Encapsulated by Parylene Film. Sensors 2013, 13, 4138-4145.
Kan T, Aoki H, Binh-Khiem N, Matsumoto K, Shimoyama I. Ratiometric Optical Temperature Sensor Using Two Fluorescent Dyes Dissolved in an Ionic Liquid Encapsulated by Parylene Film. Sensors. 2013; 13(4):4138-4145.
Kan, Tetsuo; Aoki, Hironori; Binh-Khiem, Nguyen; Matsumoto, Kiyoshi; Shimoyama, Isao. 2013. "Ratiometric Optical Temperature Sensor Using Two Fluorescent Dyes Dissolved in an Ionic Liquid Encapsulated by Parylene Film." Sensors 13, no. 4: 4138-4145.