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Thermo-optical characterization of fluorescent rhodamine B based temperature-sensitive nanosensors using a CMOS MEMS micro-hotplate.

Chauhan VM, Hopper RH, Ali SZ, King EM, Udrea F, Oxley CH, Aylott JW - Sens Actuators B Chem (2014)

Bottom Line: The fluorescence response of all nanosensors dispersed across the surface of the MEMS device was found to decrease in an exponential manner by 94%, when the temperature was increased from 25 °C to 145 °C.The MEMS device used for this study could prove to be a reliable, low cost, low power and high temperature micro-hotplate for the thermo-optical characterisation of sub-micron sized particles.The temperature-sensitive nanosensors could find potential application in the measurement of temperature in biological and micro-electrical systems.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Biophysics and Surface Analysis, School of Pharmacy, University of Nottingham, Boots Science Building, University Park, Nottingham NG7 2RD, UK.

ABSTRACT

A custom designed microelectromechanical systems (MEMS) micro-hotplate, capable of operating at high temperatures (up to 700 °C), was used to thermo-optically characterize fluorescent temperature-sensitive nanosensors. The nanosensors, 550 nm in diameter, are composed of temperature-sensitive rhodamine B (RhB) fluorophore which was conjugated to an inert silica sol-gel matrix. Temperature-sensitive nanosensors were dispersed and dried across the surface of the MEMS micro-hotplate, which was mounted in the slide holder of a fluorescence confocal microscope. Through electrical control of the MEMS micro-hotplate, temperature induced changes in fluorescence intensity of the nanosensors was measured over a wide temperature range. The fluorescence response of all nanosensors dispersed across the surface of the MEMS device was found to decrease in an exponential manner by 94%, when the temperature was increased from 25 °C to 145 °C. The fluorescence response of all dispersed nanosensors across the whole surface of the MEMS device and individual nanosensors, using line profile analysis, were not statistically different (p < 0.05). The MEMS device used for this study could prove to be a reliable, low cost, low power and high temperature micro-hotplate for the thermo-optical characterisation of sub-micron sized particles. The temperature-sensitive nanosensors could find potential application in the measurement of temperature in biological and micro-electrical systems.

No MeSH data available.


(A) Cross-section of the CMOS MEMS micro-hotplate. (B) Reflected light image of the silicon wafer of the MEMS device (scale bar = 150 μm), where a, b and c refer to the silicon dioxide membrane, tungsten heater and tungsten track, respectively. (C) Image of MEMS devices mounted on a circuit board (scale bar = 1 cm).
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fig0005: (A) Cross-section of the CMOS MEMS micro-hotplate. (B) Reflected light image of the silicon wafer of the MEMS device (scale bar = 150 μm), where a, b and c refer to the silicon dioxide membrane, tungsten heater and tungsten track, respectively. (C) Image of MEMS devices mounted on a circuit board (scale bar = 1 cm).

Mentions: The MEMS micro-hotplate was developed by Cambridge CMOS Sensors Ltd and used as a tool to characterize the fluorescence response of temperature-sensitive nanosensors. The device consists of a multi-ring shaped resistive heater element, fabricated using CMOS tungsten metallization, embedded in a silicon dioxide membrane, Fig. 1A. Tungsten metallisation is ideally suited for micro-hotplates due to its high melting point and mechanical strength [35]. A resistive temperature sensing element is embedded within the CMOS oxide layers and both the sensor and the membrane have a silicon nitride passivation layer on top of them. The membrane was formed by back-etching using a post-CMOS deep reactive ion etch (DRIE) at a MEMS foundry. Unlike wet anisotropic etching, deep reactive ion etching allows easy formation of a circular membrane which has better mechanical stability because there are no sharp corners where stresses are concentrated. The metalized heater track is 4 μm wide. It has a diameter of 150 μm, covering a circular area of 0.017 mm2, and is thermally isolated in the centre of a 560 μm diameter membrane, Fig. 1B. For this study four MEMS devices of identical design were epoxied and wire bonded to a metalized ceramic circuit board from which electrical connections were made to a power supply and the multi-meter. The whole assembly is small enough to be mounted in the slide holder of a confocal microscope, Fig. 1C.


Thermo-optical characterization of fluorescent rhodamine B based temperature-sensitive nanosensors using a CMOS MEMS micro-hotplate.

Chauhan VM, Hopper RH, Ali SZ, King EM, Udrea F, Oxley CH, Aylott JW - Sens Actuators B Chem (2014)

(A) Cross-section of the CMOS MEMS micro-hotplate. (B) Reflected light image of the silicon wafer of the MEMS device (scale bar = 150 μm), where a, b and c refer to the silicon dioxide membrane, tungsten heater and tungsten track, respectively. (C) Image of MEMS devices mounted on a circuit board (scale bar = 1 cm).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4376176&req=5

fig0005: (A) Cross-section of the CMOS MEMS micro-hotplate. (B) Reflected light image of the silicon wafer of the MEMS device (scale bar = 150 μm), where a, b and c refer to the silicon dioxide membrane, tungsten heater and tungsten track, respectively. (C) Image of MEMS devices mounted on a circuit board (scale bar = 1 cm).
Mentions: The MEMS micro-hotplate was developed by Cambridge CMOS Sensors Ltd and used as a tool to characterize the fluorescence response of temperature-sensitive nanosensors. The device consists of a multi-ring shaped resistive heater element, fabricated using CMOS tungsten metallization, embedded in a silicon dioxide membrane, Fig. 1A. Tungsten metallisation is ideally suited for micro-hotplates due to its high melting point and mechanical strength [35]. A resistive temperature sensing element is embedded within the CMOS oxide layers and both the sensor and the membrane have a silicon nitride passivation layer on top of them. The membrane was formed by back-etching using a post-CMOS deep reactive ion etch (DRIE) at a MEMS foundry. Unlike wet anisotropic etching, deep reactive ion etching allows easy formation of a circular membrane which has better mechanical stability because there are no sharp corners where stresses are concentrated. The metalized heater track is 4 μm wide. It has a diameter of 150 μm, covering a circular area of 0.017 mm2, and is thermally isolated in the centre of a 560 μm diameter membrane, Fig. 1B. For this study four MEMS devices of identical design were epoxied and wire bonded to a metalized ceramic circuit board from which electrical connections were made to a power supply and the multi-meter. The whole assembly is small enough to be mounted in the slide holder of a confocal microscope, Fig. 1C.

Bottom Line: The fluorescence response of all nanosensors dispersed across the surface of the MEMS device was found to decrease in an exponential manner by 94%, when the temperature was increased from 25 °C to 145 °C.The MEMS device used for this study could prove to be a reliable, low cost, low power and high temperature micro-hotplate for the thermo-optical characterisation of sub-micron sized particles.The temperature-sensitive nanosensors could find potential application in the measurement of temperature in biological and micro-electrical systems.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Biophysics and Surface Analysis, School of Pharmacy, University of Nottingham, Boots Science Building, University Park, Nottingham NG7 2RD, UK.

ABSTRACT

A custom designed microelectromechanical systems (MEMS) micro-hotplate, capable of operating at high temperatures (up to 700 °C), was used to thermo-optically characterize fluorescent temperature-sensitive nanosensors. The nanosensors, 550 nm in diameter, are composed of temperature-sensitive rhodamine B (RhB) fluorophore which was conjugated to an inert silica sol-gel matrix. Temperature-sensitive nanosensors were dispersed and dried across the surface of the MEMS micro-hotplate, which was mounted in the slide holder of a fluorescence confocal microscope. Through electrical control of the MEMS micro-hotplate, temperature induced changes in fluorescence intensity of the nanosensors was measured over a wide temperature range. The fluorescence response of all nanosensors dispersed across the surface of the MEMS device was found to decrease in an exponential manner by 94%, when the temperature was increased from 25 °C to 145 °C. The fluorescence response of all dispersed nanosensors across the whole surface of the MEMS device and individual nanosensors, using line profile analysis, were not statistically different (p < 0.05). The MEMS device used for this study could prove to be a reliable, low cost, low power and high temperature micro-hotplate for the thermo-optical characterisation of sub-micron sized particles. The temperature-sensitive nanosensors could find potential application in the measurement of temperature in biological and micro-electrical systems.

No MeSH data available.