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Ratiometric optical temperature sensor using two fluorescent dyes dissolved in an ionic liquid encapsulated by Parylene film.

Kan T, Aoki H, Binh-Khiem N, Matsumoto K, Shimoyama I - Sensors (Basel) (2013)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: 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. kan@leopard.t.u-tokyo.ac.jp

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.

No MeSH data available.


Sensor response to temperature changes: (a) measurements for individual dyes and (b) ratiometric measurement.
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f5-sensors-13-04138: Sensor response to temperature changes: (a) measurements for individual dyes and (b) ratiometric measurement.

Mentions: The relationship between the temperature and fluorescence intensity was investigated for each dye. The temperature was varied by heating the sensor with a silicon rubber heater. The sensor was heated from 25 °C to 68 °C (and then cooled from 68 °C to 25 °C) using the heater, and the fluorescence intensity of the droplet was simultaneously measured. Figure 5(a) shows plots of the intensities of each dye. The fluorescence intensity of each dye was normalized by its fluorescence intensity at 25 °C. The fluorescence intensity for both dyes decreased with increasing temperature. We performed intensity measurements in ascending steps (increasing temperature) and descending steps (decreasing temperature). The hysteresis was sufficiently small that it was neglected. A linear fit to the temperature data was obtained using the least-mean-squares method, resulting in temperature dependences of the RhB and Rh110 intensities of −1.2%/K and −0.27%/K, respectively. Figure 5(b) shows a plot of the IRhB/IRh110 ratio, where IRhB and IRh110 denote the fluorescence intensities of RhB and Rh110, respectively. The temperature dependency of the ratio was −1.0%/K. Assuming that the fits were accurate, the sensor accuracy was defined as the difference between the measured fluorescence intensity and the fluorescence intensity calculated from the linear fit. A mean accuracy of 1.9 °C was obtained by calculating the accuracy of each measured point in the ascending direction in Figure 5(b). The temperature precision was determined to be 3.7 °C, which corresponded to the largest standard deviation of the sensor output (i.e., the error bars) observed in the ratiometric data.


Ratiometric optical temperature sensor using two fluorescent dyes dissolved in an ionic liquid encapsulated by Parylene film.

Kan T, Aoki H, Binh-Khiem N, Matsumoto K, Shimoyama I - Sensors (Basel) (2013)

Sensor response to temperature changes: (a) measurements for individual dyes and (b) ratiometric measurement.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3673075&req=5

f5-sensors-13-04138: Sensor response to temperature changes: (a) measurements for individual dyes and (b) ratiometric measurement.
Mentions: The relationship between the temperature and fluorescence intensity was investigated for each dye. The temperature was varied by heating the sensor with a silicon rubber heater. The sensor was heated from 25 °C to 68 °C (and then cooled from 68 °C to 25 °C) using the heater, and the fluorescence intensity of the droplet was simultaneously measured. Figure 5(a) shows plots of the intensities of each dye. The fluorescence intensity of each dye was normalized by its fluorescence intensity at 25 °C. The fluorescence intensity for both dyes decreased with increasing temperature. We performed intensity measurements in ascending steps (increasing temperature) and descending steps (decreasing temperature). The hysteresis was sufficiently small that it was neglected. A linear fit to the temperature data was obtained using the least-mean-squares method, resulting in temperature dependences of the RhB and Rh110 intensities of −1.2%/K and −0.27%/K, respectively. Figure 5(b) shows a plot of the IRhB/IRh110 ratio, where IRhB and IRh110 denote the fluorescence intensities of RhB and Rh110, respectively. The temperature dependency of the ratio was −1.0%/K. Assuming that the fits were accurate, the sensor accuracy was defined as the difference between the measured fluorescence intensity and the fluorescence intensity calculated from the linear fit. A mean accuracy of 1.9 °C was obtained by calculating the accuracy of each measured point in the ascending direction in Figure 5(b). The temperature precision was determined to be 3.7 °C, which corresponded to the largest standard deviation of the sensor output (i.e., the error bars) observed in the ratiometric data.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: 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. kan@leopard.t.u-tokyo.ac.jp

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.

No MeSH data available.