Thin Film Resistance Temperature Detector Research Articles

Independent microscale sensing of phase interface and surface temperature during droplet evaporation

Despite the important and pervasive nature of evaporative heat transfer phenomena, fundamental questions still remain about the microscopic processes that occur in and around individual droplets on a surface. In order to understand the underlying physics behind evaporative heat transfer, it is critical to have information at the individual droplet level regarding the surface temperature distribution with time as well as the location and speed of the moving multiphase contact line (MCL). In this work, a multifunctional microscale device comprised of a resistance heater, an array of spatially distributed thin-film resistance temperature detectors, and a phase interface sensing capacitance micro-sensor array has been utilized to measure the local heat transfer characteristics and MCL behavior simultaneously for the evaporation of individual sessile water droplets on a horizontal heated surface. The resistance- and capacitance-based operating principles of the micro-device means that it is capable of detecting temperature changes and tracking MCL at the microscale in real time even for applications with limited or no visibility such as within thermal management hardware or processing equipment. Importantly, having knowledge of the MCL’s location and speed with microscale precision allows for its influence on surface temperature and heat transfer to be directly studied rather than inferred. Results show that the MCL passage precedes the change in local surface temperature and the duration of the time difference between these events depends on the MCL’s speed. In addition, the passage of the MCL accounts for more than 70% of the overall temperature change during the evaporation process.

A Cu/Ni alloy thin-film sensor integrated with current collector for in-situ monitoring of lithium-ion battery internal temperature by high-throughput selecting method

The high-energy-density lithium-ion batteries (LIBs) are susceptible to thermal runaway and lead to safety incidents. Monitoring the internal temperature of LIBs is a promising way to forewarn its thermal runaway. However, the current external temperature sensors show high delay and poor accuracy, and the built-in temperature sensors are incompatible with the assembly process and may damage the battery. Thus, a reliable real-time internal battery temperature monitoring sensor is desired. In this study, a high-throughput selected thin-film resistance temperature detector (TFRTD) is proposed. The TFRTD is integrated between the collectors of the pouch LIB, which is compatible with the battery assembly process. The built-in TFRTD responds 82% faster and measures 33% more accurately than an external RTD, allowing real-time monitoring of internal battery temperature at different current rates. With a discharge rate of 0.5 C, the internal temperature can be monitored to be 0.57 °C higher than the external temperature in a battery with a capacity of only 0.1 Ah. Cycling tests show that the battery with a built-in TFRTD has a capacity retention rate of 92.71% after 100 cycles, and the TFRTD has a limited impact on battery performance. Therefore, the developed novel TFRTD can be used to analyze the battery heating process under different conditions and has some potential for engineering applications.

Response Time of a Thin-Film Resistance Temperature Detector (RTD) for High-Intensity Focused Ultrasound (HIFU) Phantom Applications

The thermal response time of a thin-film resistance temperature detector (RTD) array sensor was measured for a high-intensity focused ultrasound (HIFU) phantom. As the temperature inside materials change rapidly within several seconds, it is important to have a temperature sensor with a fast response time to evaluate their performance. However, previous methods for measuring thermal response time were not suitable for thin-film sensors, and there were no quantitative data available. In this study, we used a liquid drop method to measure the thermal time constant of the thin-film RTD, which was found to be 1.0 ± 0.2 ms. This indicates that the thin-film RTD array sensor has a sufficiently fast response time to detect sudden temperature changes inside the tissue-mimicking material (TMM) for validating HIFU devices.

Thin-Film Platinum Resistance Temperature Detector with a SiCN/Yttria-Stabilized Zirconia Protective Layer by Direct Ink Writing for High-Temperature Applications.

In situ temperature monitoring of curved high-temperature components in extreme environments is challenging for a variety of applications in fields such as aero engines and gas turbines. Recently, extrusion-based direct ink writing (DIW) has been utilized to fabricate platinum (Pt) resistance temperature detectors (RTDs). However, the current Pt RTD prepared by DIW technology suffers from a limited temperature range and poor high-temperature stability. Here, DIW technology and yttria-stabilized zirconia (YSZ)-modified precursor ceramic film packaging have been used to build a Pt RTD with high-temperature resistance, small disturbance, and high stability. The results indicate that the protective layer formed by the liquid phase anchors the Pt particles and reduces the agglomeration and volatilization of the Pt sensitive layer at high temperature. Attributed to the SiCN/YSZ protective layer, the temperature resistance curve of the Pt RTD in the range of 50-800 °C has little deviation from the fitting curve, and the fitting correlation coefficient is above 0.9999. Interestingly, the Pt RTD also has high repeatability and stability. The high temperature resistance drift rate is only 0.05%/h after 100 h of long-term testing at 800 °C and can withstand butane flame up to ∼1300 °C without damage. Moreover, the Pt RTD can be conformally deposited on the outer ring of aerospace bearings by DIW technology and then realize on-site, nondestructive, and real-time monitoring of bearing temperature. The fabricated Pt RTD shows great potential for high-temperature applications, and the novel technology proposed provides a feasible pathway for temperature monitoring of aeroengine internal curved hot-end components.

An enhanced thin-film resistance temperature detector and its application for catalyst layer surface temperature measurement inside PEMFC

Temperature detection is of vital significance for the thermal management of proton exchange membrane fuel cells (PEMFCs). In this work, a robust Au thin-film resistance temperature detector (RTD) was fabricated based on the micro-electro-mechanical system (MEMS) to achieve temperature monitoring inside PEMFC. Low-temperature heat treatment was carried out to promote the performance of RTD, and was confirmed to help achieve good linearity and small thermal hysteresis. Combined with X-ray diffusion (XRD) Rietveld refinement and morphology analysis, particularly the lattice strain and dislocation calculation, low-temperature heat treatment is supposed to help eliminate lattice defects and residual strains in the film. Subsequently, this prepared RTD was applied to measure cathode catalyst layer (CCL) temperature inside PEMFC under different relative humidity (RH) and current loads. The results show that current loads are positively related to temperature variation. The higher the current, the more Joule and irreversible heat are generated. The RH of anode and cathode has a more complex impact on temperature evolution, depending on the water concentration in the electrode sites, which is not only affected by RH, but also by the oxygen reduction reaction (ORR). Too high water contents in the electrode area would bring about flooding, while too low would result in membrane drying, so both of them cause different levels of ohmic and mass transport loss, hence inducing temperature variations. This work is supposed to benefit the research of RTD enhancement and thermal state inside PEMFC.

Flexible Pt Thin-Film Resistance Temperature Detector with Improved Stretchability

Flexible Pt Thin-Film Resistance Temperature Detector with Improved Stretchability

Application of 3-omega method for thin-film heat flux gauge calibration

Double-sided thin-film resistance temperature detector (RTD) heat flux gauges (HFGs) are commonly used to characterize heat transfer rates in high-heat flux environments with complex flow features. These gauges comprise two thin-film RTDs on opposing sides of a dielectric. To deduce accurate heat flux, the RTDs must be properly calibrated and the material properties of the dielectric must be characterized. This study presents a complete gauge characterization method for sensors of this type by applying standard calibration procedures with specially-designed RTDs capable of utilizing the 3-omega method. The 3-omega method quantifies the thermal conductivity and thermal product of a material by measuring the response of a specially designed heater/thermometer deposited on the substrate. This study shows the 3-omega method enables RTD calibrations and thermal property determination over a range of temperatures for individual gauges, reducing the uncertainty in calculated heat flux. Although the method is quite general, this study utilized platinum RTDs with a polyimide dielectric, which is common in turbomachinery applications. The thermal properties obtained through this method agree with previous characterization efforts; however, discrete characterization of seven gauges shows that gauge-to-gauge variation in the dielectric could influence measured heat flux by as much as 30%. This study also builds the framework to characterize the thermal conductivity of the adhesive layer beneath the gauge which is necessary to mount the sensors to the test article. Although often uncharacterized, the adhesive thermal conductivity has a significant impact on matching experimental measurements to simulations. Additionally, this study found that if the thermal conductivity of the dielectric is constant (an assumption that holds for the present study), an in-situ RTD calibration can be performed. In-situ RTD calibration and traditional method RTD calibration agreed to within 0.1%. Overall, this work has practical implications in obtaining high quality measurements from HFGs of this type.

Pt thin-film resistance temperature detector on flexible Hastelloy tapes

Platinum (Pt) thin-film resistance temperature detector was fabricated on the flexible Hastelloy tapes using magnetron sputtering and MEMS processes. NiCrAlY buffer layer and AlON/Al2O3 insulating layer were deposited on the tapes for stress release and electrical insulation. Post annealing was applied to improve the stability of the sensors. The performance of the sensor was calibrated with temperature up to 550 °C. Compared with the sensor on the alumina ceramic substrate, the sensor on Hastelloy tapes have much smaller thermal hysteresis, higher linearity and excellent stability. Moreover, this flexible sensor can be easily integrated with the metallic components by the welding and the maximum curvature of the sensor is 2 cm−1. This Pt thin-film temperature sensor has great potential in the surface temperature measurement of hot components in harsh environment.

Characterization of On-Foil Sensors and Ultra-Thin Chips for HySiF Integration

The characterization of multiple mechanically flexible passive and active electronic components, namely on-foil temperature sensor, relative humidity sensor, and ultra-thin microcontroller unit (MCU) integrated circuit (IC) is presented. These components are readily available for Hybrid System-in-Foil (HySiF) integration, which combines the merits of the high-performance silicon chips with the large-area electronics. The 60-nm thin-film resistance temperature detector (RTD) is fabricated on different substrates and the extracted temperature coefficient ranges from 0.002 to 0.003( $\Omega/\Omega$ )/°C. Furthermore, the capacitive relative humidity sensor is fabricated by utilizing a polymeric sensing dielectric material that is compatible with those polyimides used in ultra-thin chip embedding. The $1-\mu \text {m}$ thick sensor achieves a fast adsorption rise time of $\text {54 ms}$ and a spontaneous desorption fall time of $\text {750 ms}$ . For flexible ICs packaging and HySiF integration, microcontroller chips are back-thinned to a thickness of about ${30}~\mu \text {m}$ . The characterization of the MCU after the thinning process step showed undegraded performance of the integrated analog-to-digital converter in terms of linearity. However, a drop in the on-chip temperature sensor sensitivity is observed for the thin chips and significant degradation in the period jitter of the high-frequency RC oscillator is measured. Finally, continuity tests are performed to validate the functionality of the ultra-thin MCUs when embedded using the Chip-Film Patch (CFP) flexible package.

Portable and Battery-Powered PCR Device for DNA Amplification and Fluorescence Detection.

Polymerase chain reaction (PCR) is a technique for nucleic acid amplification, which has been widely used in molecular biology. Owing to the limitations such as large size, high power consumption, and complicated operation, PCR is only used in hospitals or research institutions. To meet the requirements of portable applications, we developed a fast, battery-powered, portable device for PCR amplification and end-point detection. The device consisted of a PCR thermal control system, PCR reaction chip, and fluorescence detection system. The PCR thermal control system was formed by a thermal control chip and external drive circuits. Thin-film heaters and resistance temperature detectors (RTDs) were fabricated on the thermal control chip and were regulated with external drive circuits. The average heating rate was 32 °C/s and the average cooling rate was 7.5 °C/s. The disposable reaction chips were fabricated using a silicon substrate, silicone rubber, and quartz plate. The fluorescence detection system consisted a complementary metal-oxide-semiconductor (CMOS) camera, an LED, and mirror units. The device was driven by a 24 V Li-ion battery. We amplified HPV16E6 genomic DNA using our device and achieved satisfactory results.

Fabrication and characterization of nickel thin film as resistance temperature detector

In practical applications, thin film resistance temperature detectors (RTD) are often used in the environments that the attached substrates cannot stand high temperature. Therefore, it is necessary to prepare thin film RTDs by a low temperature process. In this study, the fabrication of nickel (Ni) thin film RTDs at low temperatures is investigated by direct-current (DC) magnetron sputtering. It is found that the dense and uniform Ni thin film can be prepared even at room temperature. The effects of sputter pressure and power on thin film microscopic morphology and structure are also investigated. The Ni thin film RTDs prepared at room temperature exhibit a value of temperature coefficient of resistance (TCR) about 3000 ppm/°C and excellent repeatability under cycling temperatures.

Development of a Fast-Response Diamond Calorimeter Heat Transfer Gauge

A robust fast-response calorimeter heat transfer gauge called the Diamond Heat Transfer Gauge has been developed for use in transient hypersonic ground test facilities. Gauges have been produced using discs of synthetic diamond thick as calorimeters with platinum thin-film resistance temperature detectors on the rear surface to measure temperature rise. Depending on calorimeter thickness and the grade of diamond used, the 99% rise time of the gauges is between 10.6 and . Test-time heat fluxes have been measured with the new gauges on a sharp wedge model and a blunt-nosed wedge model in flows with total enthalpies of over multiple shots in an expansion tunnel. Stagnation point measurements exceeded . Experimentally measured heat fluxes are shown to agree with surface-junction coaxial thermocouples and an empirical correlation on the stagnation point.

MEMS sensor for high resolution measurement of boiling heat transfer

We have developed a micro heat flux sensor for measuring boiling heat transfer at high-resolution. The heat flux sensor consists of two thin film resistance temperature detectors (RTDs) stacked in the substrate thickness direction. The heat flux can be calculated through the one-dimensional transient heat conduction calculation using measured two temperatures. Two kinds of experiments as preliminary test were conducted. First one is the local heat flux measurement during liquid droplet contact on the sensor substrate. The sensor successfully detected a huge heat transfer of over 3MW/m2 with a quick temperature change of ~105K/s just after droplet contact. And another is measurement of the local heat flux beneath a single pool boiling bubble. The heat flux over 1 MW/m2 induced by microlayer evaporation was measured under a bubble. The developed sensor was confirmed to be useful for the measurement of fast and local heat transfer phenomena.

Evaluation of thin film p-type single crystal silicon for use as a CMOS Resistance Temperature Detector (RTD)

Temperature monitoring and thermal management of CMOS circuits / sensors is often required for long term circuit reliability and sensors temperature compensations. The ideal solution is to co-fabricate the temperature sensors along with the CMOS circuits and other sensors using CMOS materials and the same CMOS processes. In this paper we therefore, report on the fabrication and thermal characterization of such thin film temperature sensors. The thin film Resistance Temperature Detectors (RTDs) are made of single crystal p-type silicon on a silicon substrate using a Silicon on Insulator (SOI) Complementary Metal Oxide Semiconductor (CMOS) process. The influence of thin film length and width on the response of RTDs has been investigated. Furthermore, the effects of aluminum (Al) and tungsten (W) metallization used for power tracks on the response of RTDs have been studied. To assess the performance of the RTDs based on SOI CMOS p-type silicon, in addition to sensitivity and TCR, their power consumption, linearity, hysteresis, repeatability, reproducibility and expected life span have also been evaluated. The p-type silicon RTDs consume very less power (i.e. 0.9 μW only) and demonstrate a sensitivity of 13.88 Ω / oC, which is much higher than the previously reported CMOS RTDs and widely used non-CMOS platinum RTDs. The RTDs also exhibit a linear response (98.9% fsd), an excellent repeatability and significantly low hysteresis with maximum variation of 0.2% between forward and reverse cycle. These RTDs also boast good reproducibility, within the wafer and wafer to wafer, with maximum sensitivity variation of 1.3% between different tested samples. The expected life span of the RTD is > 10 years. These inexpensive RTDs are therefore, good candidates for use as temperature sensors on CMOS circuits / sensors system.

Three-point MEMS heat flux sensor for turbulent heat transfer measurement in internal combustion engines

A heat flux sensor was developed with micro-electro-mechanical systems (MEMS) technologies for investigating turbulent heat transfer characteristics in engines. The sensor has three thin-film resistance temperature detectors (RTDs) of a square 315 µm on a side on a 900 µm diameter circle in rotational symmetry. The performances of the MEMS systems sensor were tested in an open combustion chamber and a laboratory engine. In the open chamber tests, it was revealed that the MEMS sensor can measure the wall heat fluxes reflecting flow states of gas phase. In addition, the noise was evaluated as 3.8 kW/m2 with the standard deviation against the wall heat flux of a few hundred kW/m2. From these results, it was proved that the MEMS sensor has the potential to observe turbulent heat transfer on the order over 10 kW/m2 in the engine. In the laboratory engine test, the wall heat flux for continuous 200 cycles was measured with a good signal-to-noise ratio. The noise was evaluated as 13.4 kW/m2 with the standard deviation despite the noisy environment. Furthermore, it was proved that the MEMS sensor has the comparable scale with the turbulence in the engine because the three adjacent detectors measured similar but different phase oscillations in the local instantaneous heat fluxes. In addition, a heat flux vector reflecting the state of the local instantaneous heat transfer was visualized by the adjacent three-point measurement. It is expected that the three-point MEMS sensor will be a useful tool for the engine heat transfer research.

Thin-film resistance temperature detector array for the measurement of temperature distribution inside a phantom

A thin-film resistance temperature detector (RTD) array is proposed to measure the temperature distribution inside a phantom. HIFU (high-intensity focused ultrasound) is a non-invasive treatment method using focused ultrasound to heat up a localized region, so it is important to measure the temperature distribution without affecting the ultrasonic field and heat conduction. The present 25 µm thick PI (polyimide) film is transparent not only to an ultrasonic field, because its thickness is much smaller than the wavelength of ultrasound, but also to heat conduction, owing to its negligible thermal mass compared to the phantom. A total of 33 RTDs consisting of Pt resistors and interconnection lines were patterned on a PI substrate using MEMS (microelectromechanical systems) technology, and a polymer phantom was fabricated with the film at the center. The expanded uncertainty of the RTDs was 0.8 K. In the experimental study using a 1 MHz HIFU transducer, the maximum temperature inside the phantom was measured as 70.1 °C just after a HIFU excitation of 6.4 W for 180 s. The time responses of the RTDs at different positions also showed the residual heat transfer inside the phantom after HIFU excitation. HIFU results with the phantom showed that a thin-film RTD array can measure the temperature distribution inside a phantom.

Fabrication and characterization of ITO thin film resistance temperature detector

Indium-tin-oxide (ITO) thin film resistance temperature detectors (RTD) were fabricated on alumina substrates by RF sputtering in this study. The scanning electron microscope (SEM) and atomic force microscope (AFM) images show that the thin films deposited under argon and oxygen were more smooth and dense than those deposited without oxygen. The film became more stoichiometric when no more than 20sccm oxygen was introduced. The XRD result shows that ITO deposited under argon and oxygen had an In2O3 crystal structure with a preferred orientation of (222) and the film deposited without oxygen showed a preferred orientation of (400). High temperature tests revealed that the resistance changed linearly with the temperature and the RTD had different temperature coefficient of resistance (TCR) in different temperature ranges. The absolute value of TCR was large and the RTDs showed promising application at high temperature, especially from 600 °C to 900 °C.

Design, fabrication and characterization of thin film resistances for heat flux sensing application

The article presents the design, fabrication and characterization of platinum thin-film Resistance Temperature Detectors (RTDs) for heat flux sensing applications. The microfabrication process is described and the thin films are analysed by several methods including SEM, XRD and profilometry. Estimation of experimental uncertainties is performed. The influence of annealing, self-heating, 2-wire and 4-wire connections are studied. The analysis and experimental results show that the RTDs have a good repeatability when an annealing process is performed and a maximal injected current are used. A measurement uncertainty of 0.14°C is achieved. The observed Temperature Coefficient Ratio is sufficient to ensure variation of the resistance in the temperature range. The heat flux measurements made with the sensor are validated in a dedicated test bench and present a good repeatability.

An approach for in situ measurement of anode temperature during the growth of self-ordered nanoporous anodic alumina thin films: Influence of Joule heating on pore microstructure

Anodic aluminium oxide (AAO) thin films, containing hexagonally ordered nanopores, are widely used as templates for fabricating a large number of zero and one- dimensional functional nanostructures such as: nanodots, nanowires and nanotubes. The localized pore temperature developed due to the heat generation phenomenon during anodization plays a key role in the growth morphology of the nanoporous structure. The influence of temperature on the electrochemical process of anodization is generally evaluated by considering the electrolyte temperature, while little importance is given to the localized electrode temperature. In the present work, nanoporous alumina templates were prepared using a two step anodization process with oxalic acid as electrolyte under different bath temperatures and anodizing potentials. We report a novel approach to measure the in situ anode temperature during the anodization process that uses a Pt thin film Resistance Temperature Detector sensor which is deposited on partially fabricated alumina through anodization. The in situ anode temperature has been recorded at different anodization conditions and their contribution to the rise in the anode temperature is presented. Our results indicate that Joule heating is a major source of heat developed during the anodization

Temperature Coefficient of Thin Film Resistance Temperature Detectors for Improved Heat Flux Sensors

The measurement of thermal properties or internal or external boundary conditions requires temperature and heat flux data. Both information can be provided by heat flux sensors. The one consisting in measuring temperature at various locations within the wall and using inverse method to estimate wall temperature and heat flux is among those providing the lowest measurement bias for transient heat flux measurement. However, this very accurate sensor requires time consuming technical work for microthermocouples implementation and due to the welding, one cannot locate precisely the temperature measurement. The idea developed in this work is to replace the wire microthermocouples by thin film resistance temperature detectors deposited on polymer substrate in order to ease the fabrication and to increase the accuracy of heat flux sensor. As the deposited sensors are RTDs, a preliminary study is performed showing the effect of the metal as well as the processing conditions on the electrical resistivity and temperature coefficient of copper and aluminum thin film