Temperature Microsensors Research Articles

Experimental pool boiling investigations of FC-72 on silicon with artificial cavities and integrated temperature microsensors

In this experimental study, fluorinert FC-72 is boiled on a silicon chip with artificial cavities and integrated microsensors. The horizontal silicon chip with dimensions of 39.5 × 19 × 0.38 mm is completely immersed in FC-72. The integrated nickel–titanium temperature microsensors on the back of the chip are calibrated individually and exhibit a near-linear increase of electrical resistance with temperature. The applied heat fluxes and the resulting wall superheat at the boiling surface are varied by means of an integral thin-film resistance heater (95% Al, 4% Cu and 1% Si), also on the back of the silicon chip. Artificial cylindrical cavities with a mouth diameter of 10 μm and depths of 40, 80 or 100 μm situated above the microthermometers serve as artificial nucleation sites, due to trapped vapour. Bubble growth rates, frequencies, departure diameters of bubbles and waiting times between bubbles from an isolated cavity for different wall superheats and pressures were obtained by analysing high-speed video images and the simultaneously measured temperature below the artificial cavity.

Fabrication of flexible micro-sensors and flow field of stainless steel-based micro-reformer by micro-electro-mechanical-systems process

Recent advances in micro-fuel cells have increased the demand for hydrogen. Therefore, a micro-reformer must be developed. Numerous portable electric devices are extremely small and reformers must therefore be shrunk and combined with micro-fuel cells. The mass production of micro-reformers raises various problems that are yet to be solved, such as the measurement of their internal temperature and flow rate. Such issues influence the efficiency of the micro-reformers. To our knowledge, no investigation has yet properly elucidated the internal operation of micro-reformers. Accordingly, in this work, a flexible micro-temperature sensor, a micro-heater, a micro-flow sensor and the flow field of a stainless steel-based micro-reformer were fabricated by micro-electro-mechanical-systems (MEMS) fabrication technique. The fabrication technique has the advantages of (1) small size, (2) flexible but precise measurement positions, and (3) mass production process.

Pressure and temperature microsensor based on surface acoustic wave

A novel microsensor based on a surface acoustic wave is reported, which is to measure pressure and temperature simultaneously. The kernel structure and design theory of this sensor with a single sensing unit are introduced. The excellent agreement between the pressure and temperature results measured by the sensor and the direct measurement data is presented.

Temperature sensitivity of silica micro-resonators

Optical resonance shifts are measured against temperature changes for different silica beads ranging from 80 to 450 µm in diameter. A micro-bead is fabricated by hydrogen flame fusing the tip of a single mode silica fibre/taper, and coupled to a fibre taper of submicrometre diameter. The coupling system in whispering-gallery modes is placed in an insulated cell. The air in the cell is slowly heated up from room temperature to about 10 K higher, and red shifts of a resonance wavelength during the heating process are recorded. Linear dependence of the wavelength shift versus the temperature rise is observed for all the tested micro-resonators. The measured sensitivity for beads greater than 200 µm in size closely matches the analytical value based on bulk material properties of silica thermal expansion and the thermo-optic effect. For smaller micro-beads, however, the measured sensitivity increases with shrinking bead size. The ultra-high resolution of such a kind of temperature micro-sensor and its potential applications are addressed.

Basic investigation of microtemperature sensor by means of a novel transmission-line technique using a temperature-sensitive Li–Zn–Cu ferrite substrate

The polycrystalline Mn-substituted Li–Zn–Cu ferrite exhibits a very strong temperature dependence of magnetic properties, high natural resonance frequency, and high resistivity. The authors carried out the basic investigations of the temperature sensor using this new temperature-sensitive ferrite. As the first step, the temperature-sensitive LC resonance circuit using the Li–Zn–Cu ferrite chip inductor was fabricated, and the temperature dependence of its input impedance was evaluated. The resonance frequency was decreased linearly with a large temperature coefficient. Furthermore, it was also found that the input impedance in a constant frequency operation indicated extremely temperature dependence. In order to integrate and miniaturize the temperature sensing device, a possibility of the integrated temperature-sensitive LC circuit by means of the transmission-line technique was investigated. For our motivation, the monolithic integrated temperature sensor using spiral strip-line with Li–Zn–Cu ferrite substrates, which has the temperature dependent magnetic property, was simulated by the electromagnetic field and the equivalent circuit analysis. It was clarified that the monolithic sensor exhibited remarkable temperature dependent input impedance as well as the temperature-sensitive LC resonance circuit.

Micro thermoindicators and optical-electronic temperature control for microfluidic applications

The authors report the design and implementation of sensing and control of local temperature in polydimethylsiloxane microfluidic reaction chip, based on the fabrication of a microtemperature sensor with thermochromic color bars and the associated optical and electronic feedback controls. The thermochromic color bar demonstrates easy and accurate local temperature monitoring. In combination with a microheater, this contactless microchip temperature control approach may have wide application potentials in microchemical and microbiological analyses.

In situ diagnosis of micrometallic proton exchange membrane fuel cells using microsensors

This work utilizes the microsensors that are fabricated on metallic bipolar plates to measure temperature and humidity in an operating micro-proton exchange membrane fuel cell (PEMFC). Bipolar plates were constructed of stainless steel (SS-304), and the flow channel was formed on a stainless steel substrate by wet etching. The micro-temperature and humidity sensors were fabricated using micro-electro-mechanical-systems (MEMS) technology. The sensors were located on the flow channel rib. Experimental results demonstrate that the operating temperature of fuel cell was 41.54 °C, which was measured by a micro-temperature sensor and the temperature outside the fuel cell was 37 °C, measured using a thermocouple. The gas flow rate of H 2/O 2 was 200/200 ml min −1 without humidification. The maximum power density of the fuel cell without and with microsensors on bipolar plates was 142 mW cm −2 and 56 mW cm −2, respectively.

Rapid Manufacturing of Intelligent Mold With Embedded Microsensors

The objectives of this research are to integrate the laser-powered direct metallic rapid tooling (RT) system and the microelectromechanical-system (MEMS)-based microtemperature sensors, and to develop the intelligent direct metallic RT mold with embedded MEMS-based microsensors. Since the quantity demand for complicated mold of high-class products is increasing, the development of RT technology is also growing correspondingly fast. With the continuing improvement of semiconductor fabrication and MEMS techniques, it allows us to fabricate much smaller sensors. The MEMS-based microtemperature sensors have been successfully fabricated by MEMS technology. The sensors have been shown to have temperature effect, and were able to obtain accurate temperature measurement after calibration with real temperature coefficient of resistance (TCR) ranging from -0.294 to -0.366%/degC. This microsensor-embedded approach is proposed in order to rapidly measure global and local temperature and pressure distribution inside the RT's core and cavity during the injection, hold, and cooling process. This research's approach with MEMS-based microtemperature sensors has demonstrated the feasibility and the advancement of another milestone in automated injection molding

Thermometric characteristics approximation of germanium film temperature microsensors by orthonormal polynomials

Approximations of thermometric characteristics of germanium film temperature microsensors are presented using a mathematical approach based on their expansion with orthonormal polynomials. A weighted orthonormal polynomial expansion method (OPEM) is applied, involving the experimental errors of calibration test data at every point. The thermometric functions R(T) and T(R) of resistance and temperature are described in the whole temperature range (1.7–300K) and in three subintervals (1.7–20, 20–150, and 150–300K). The absolute, relative, and specific sensitivities of the sensor, as well as the main approximation characteristics, are discussed. The OPEM is extended to obtain a mathematical description of R(T) and T(R) functions by usual polynomial coefficients calculated by orthonormal ones. A comparison between maximal relative deviations of R(T) and T(R) three-interval approximations, correspondingly, by usual and orthonormal polynomials, is presented. Numerical results of the approximation parameters of these type of temperature sensors are shown in the figures and tables.

A microfluidic gel valve device using reversible sol–gel transition of methyl cellulose for biomedical application

We have fabricated a microfluidic gel valve device that used reversible sol–gel transition of methyl cellulose (MC). A microheater and a microtemperature sensor were implemented in each microchannel in the gel valve device. Before evaluating the performance of the gel valve device, various properties of the MC solution were investigated using viscometer, spectrophotometer, and NMR. Gelation temperature was increased as the MC concentration was increased. Clear gel, an intermediate state between clear sol and turbid gel, was found at the temperature range from 30–40°C to 50–60°C. Temperature at each microchannel of the device was measured and the effect of the temperature difference on the valve operation was elucidated. In order to have normal operation of the gel valve, it was important to keep the temperature of the heated microchannel around 60°C while keeping the temperature of the flowing microchannel below 35°C. The temperature difference between two microchannels was about 23 K when fan forced cooling (FFC) method was used. For normal performance of the gel valve device, a temporary pause of fluid flow for at least 5 s was required to complete the local gelation in the microchannel. Stable gel valve performance was obtained at the flow rates larger than 5 μl/min. The gel valve device showed no leakage up to 2.07×104 Pa.

A needle temperature microsensor for in vivo and real-time measurement of the temperature in acupoints

Abstracts A novel needle temperature microsensor measurement system was established to study the temperature characteristics in acupoints. Before used in vivo, the needle temperature microsensor was tested in vitro and proved stable, accurate and sensitive. Its measurement error was no more than ±0.1 °C by calibration. Its resolution was 0.1 °C and response time was less than 1 s. The measurement ranged from 20 to 40 °C. The in vivo experiments showed that the temperature of the acupoints ascended significantly higher than that of the left and right non-acupoints (parallel to the detected acupoints and 1.0 cm apart from them) after electroacupuncture (EA) at other acupoints, which were located on the same meridian line with the detected acupoints but 6–10 cm away from them. The results indicated that the needle temperature microsensor had a good performance in vivo. Furthermore, it supplied a reliable tool for the study of the mechanism of acupuncture and meridians.

Design of Micro-Temperature Sensor Array With Thin Film Thermocouples

We are in the process of developing a micro-temperature sensor array with T-type (copper–constantan) thin film thermocouples (TFTCs) to measure the chip temperature distribution of electronic packages. A thin aluminum nitride (AlN) layer of 100 nm thickness was deposited on a silicon substrate. AlN acts not only as an electrical insulator but also as a thermal conductor between the silicon substrate and thin film thermocouples. Copper thin film with a thickness of 50 nm and constantan thin film with the same thickness were deposited on the AlN layer. The sensor array has 10×10 junctions within a 9mm×9mm area, and each junction covers a 100μm×100μm area. Electro-thermal forces measured by TFTCs using one-dimensional steady-state heat conduction were compared with the electro-thermal forces measured by standard thermocouples, and the difference between the Seebeck coefficients of the copper material and the constantan thin film was calculated according to these measurements. In order to verify the sensor array, it was placed under two-dimensional steady-state heat conduction, and electro-thermal forces were measured and converted to temperatures. Finite element analysis simulation results were compared with the temperatures, and with experimental measurements were found to be in agreement with the simulated values.

Micro-temperature sensor array with thin-film thermocouples

A micro-temperature sensor array with thin-film thermocouples (TFTCs) is developed. The TFTCs are made with T-type (copper–constantan) thermocouples to measure chip temperature distribution of electronic packaging. The sensor array of 150 nm thickness has 10×10 junctions within a 9×9 mm area.

真空蒸着法による感温フェリ磁性薄膜の作製と基礎特性

A temperature-sensitive ferrimagnetic thin film (TFF) with 1.5 μm thickness was obtained by vacuum deposition of [Fe/Zn/Mn/Zn/Fe] multilayers on alumina substrates and subsequent sintering and annealing. The composition of the TFF is MnxZn1-xFe2O4, The sputtering methods are the most typical procedures for obtaining magnetic thin films, while the new method has a low cost and does not require a special target like that used in the sputterig methods. The magnetization of TFF depends strongly on the sintering and annealing conditions. The TFF, which was sintered for 420 min in an atmosphere of oxygen with a partial pressure of 1% at 1200°C and annealed for 1 min in an atmosphere of argon at 400°C, exhibited a maximum saturation magnetization of about 105 emu/cm3 at room temperature. For the temperature change from 0°C to 60°C, the saturation magnetization of the TFF changed about 46%. TFF with sharp thermal response can be used as a micro-temperature sensor, a thermomagnetic transducer, an enzyme sensor, and a light-magnetic device. In this paper, the sintering and annealing conditions for the TFF are the focus of our attention.

Low-Temperature Properties of Compensated Ge Films Used for Cryogenic Thermometers

AbstractLow temperature microsensors are designed for cryogenic applications. As a material for the sensors we use heavily doped compensated Ge films deposited on the semi-insulating GaAs substrates. We present the results of experimental and theoretical study of the low temperature resistance as a function of temperature and magnetic field for some models of temperature sensors. The computer simulations show a good agreement with experimental data.

A temperature microsensor for biological investigations

A microprobe for contact temperature measurements is described. It consists of a silicon cantilever with a Ni thermoresistor deposited at the unfixed end. Heat capacity of the probe and mechanical stress in Si is discussed together with contact detection methods between the sensor and a plant tissue sample. A resistance versus temperature curve is presented.

Ge-film resistance and Si-based diode temperature microsensors for cryogenic applications

New types of miniature (1.2 mm diameter×1.0 mm long) temperature sensors based on germanium (Ge) films and silicon diodes have been developed and produced. The Ge-film microthermometers are intended for use at temperatures from 1 to 400 K, and silicon microdiodes cover operating temperature range from 2 to 600 K. The designs of sensitive elements and miniature package as well as sensor characteristics are presented.

Design optimization and experimental verification of wireless IDT based microtemperature sensor

This paper presents the prediction and measurement of the phase response from awireless surface acoustic wave (SAW) device for temperature sensingapplications. This wireless sensor consists of two or more arrays of an interdigitaltransducer (IDT)and reflector pair with different IDT-reflector distances. Pulse modulatedsignals are transmitted from a remote reader system and their echoes arereturned with different time delays due to the different IDT-reflectordistances. Corresponding intermediate frequency signals are generated in a mixer and their phasedifferences are calibrated to temperature values. Using the coupled-mode theory ofSAWs, the phase characteristic relative to temperature was examined. The effectof the relative distances between the two reflector arrays is demonstrated. Theinfluence of the phase reversal location, which produces multiple temperaturevalues for a given phase difference, is also discussed and a simple solutionis illustrated. This sensor is coupled with a small planar antenna, which willbe well suited for applications that require passive and conformal sensors.

Experimental study of temperature distribution in the vicinity of film boiling

The transition of nucleate to film boiling on a flat surface is studied experimentally. In the vicinity of the boundary of a propagating center of film boiling, the distributions of the temperature, of the heat flux to liquid, of the heat-transfer coefficient, and of the velocity of motion of isotherms along an exothermal surface are obtained. The experiments are carried out in liquid nitrogen. A sapphire plate with platinum temperature microsensors deposited on it by sputtering is used as a heater. The instability of the boundary of the change of the boiling modes due to the Taylor instability of the interface is found in the film boiling region, as well as an intermediate region between film and nucleate boiling, where the heat fluxes are almost three times the critical value.

Integrated temperature microsensors for characterization and optimization of thermosonic ball bonding process

A novel ball bond process optimization method based on the thermal response of an integrated aluminum microsensor is reported. The in situ temperature during ball bonding is measured and analyzed. The ultrasonic period shows distinct stages corresponding to scrubbing of the ball on the pad, intermetallic bond growth, and ball deformation by ultrasonic softening. A peak of the signal indicates the end of interconnection growth. This can be used for bond time optimization. When optimizing bonding force, the sensor signal correlates with ball shear strength. Using this method, bonding force process windows can be determined by on-line measurements. A test measurement shows that at a chip temperature of 34/spl deg/C, the bonding force optimized by the microsensor method is 260 mN whereas it is 252 mN when using conventional shear testing for optimization. In summary, the method produces a wealth of new insights in transient thermal phenomena of the ball bonding process and promises to simplify the evaluation of process windows.