Thin Film Temperature Sensors Research Articles

Multi-point thermometry tool and in-situ measurement of temperature fields

In-situ real-time measurement of instantaneous milling temperature distribution is a key issue to realize efficient machining. For the foregoing reasons, the milling model of Inconel 718 was established, and the cloud diagram of tool temperature distribution during milling was obtained. A multi-point temperature measurement tool for milling temperature with an integrated thin-film temperature sensor was designed. The real-time temperature distribution of the tool during milling was obtained from 27 sets of milling tests. The impact of each milling parameter on the milling temperature was analyzed by ANOVA.

Study on aluminium oxide doping modification of indium oxide and thermoelectric properties

Traditional thermocouples face challenges in meeting the temperature measurement requirements of crucial aero-engine components, such as low interference, high temperature resistance, quick response, and in-situ measurement. The temperature measurement requirements mentioned above can be satisfied by thin film thermocouples, thanks to advancements in thin-film preparation technology. In this study, the indium oxide (In2O3) was calculated using first principle calculation both before and after doping. It was found that doping Aluminium oxide (Al2O3) can increase the Seebeck coefficient of In2O3. Solid-phase sintering was used to create aluminum oxide-doped In2O3 nanopowders, and thin film thermocouples were fabricated using screen printing. The thermoelectric characteristics of thin film thermocouples were studied to analyze the effects of different annealing procedures and doping concentrations. The optimal annealing process was determined to be at 1300 °C for 1 h, and the ideal doping ratio was found to be Al0.1In2O3.15. The indium oxide film doped with aluminum oxide exhibits a Seebeck coefficient that is 45.9% higher than that of the undoped indium oxide film. The thin film thermocouples underwent tests for impact and vibration resistance, laser pulse response, surface and cross-section morphology, X-ray diffraction, and thermoelectric output. It has been confirmed that doping indium oxide with aluminum oxide can increase a material's Seebeck coefficient. Additionally, a thin-film temperature sensor that has been prepared can be used in challenging conditions to meet the temperature measurement requirements of an aero engine.

Electrohydrodynamic Printed AgNPs/PR Thin Film Temperature Sensors with Micro Dimensions and Higher Temperature Measurement Capabilities

Electrohydrodynamic Printed AgNPs/PR Thin Film Temperature Sensors with Micro Dimensions and Higher Temperature Measurement Capabilities

Thin-film temperature sensors with grid-type circuits for temperature distribution measurements

Measuring the temperature of satellites is crucial for thermal control. Efficient heat control is possible when the location of the heat source can be quickly identified and the heat transfer area can be measured. Grid-type thin-film temperature sensors have been proposed for this purpose. Grid-type thin-film temperature sensors use electrohydrodynamic (EHD) inkjet printing technology, a next-generation printing technology. Sensors with high sensing resolution can be manufactured using these technologies. However, the EHD inkjet printing technology is sensitive to printing conditions, and determining the optimal conditions is crucial. Therefore, we produce inks for application in EHD inkjet printing technology and conduct experiments to validate their characteristics. In addition, we determine the optimal conditions for printing and manufacturing grid-type thin-film temperature sensors. The heating element is placed at an arbitrary location and the location of heat generation is detected using the manufactured temperature sensors. We have obtained visualization data showing the heat distribution with time. As a result, the production of a grid-type thin film temperature sensor using the printing process was confirmed. This temperature sensor was able to track the heat source and check the distribution process through which heat is transferred. Therefore, it can be expected to be used in fields that require temperature monitoring.

Aerosol jet printed resistive temperature sensors with high sensitivity

Aerosol jet printing provides a facile, cost-efficient, and environmentally friendly approach to pattern thin films with nanomaterial inks. Printed flexible resistive thin-film temperature sensors play an important role in human body temperature monitoring, soft robotics, prosthetics, and real-time temperature monitoring of large area curved surfaces due to their linear response to temperature, low-cost, scalability, and flexibility. However, the temperature coefficient of the resistance of the printed resistive temperature sensors reported in the literature is much less than that of their bulk metals. In this work, we demonstrate aerosol jet printed resistive temperature sensors with silver nanoparticle ink that have a temperature coefficient of resistance close to that of bulk silver. We report a temperature coefficient of resistance of 3.7 × 10−3 ◦C−1 for the aerosol jet printed resistive temperature sensors, the highest value yet reported in literature for resistive temperature detectors composed of thermally sintered silver nanoparticle thin films. The mechanisms for the increased performance are investigated using metrological and thermal techniques with regard to the source ink and traces. Additionally, we show that the overall sensitivity of the printed sensors can be modulated by controlling the thickness of the printed thin films. Finally, we evaluate the response of the printed resistive sensors to bending strain and humidity, including an investigation into the effects of organic passivation. Overall, this work presents printed sensors with performance on par with vacuum deposited resistive temperature detectors, enabling the fabrication technique to make an industrial impact.

La(Ca)CrO3-Filled SiCN Precursor Thin Film Temperature Sensor Capable to Measure up to 1100 °C High Temperature.

Thin-film sensors are regarded as advanced technologies for in situ condition monitoring of components operating in harsh environments, such as aerospace engines. Nevertheless, these sensors encounter challenges due to the high-temperature oxidation of materials and intricate manufacturing processes. This paper presents a simple method to fabricate high temperature-resistant oxidized SiCN precursor and La(Ca)CrO3 composite thin film temperature sensors by screen printing and air annealing. The developed sensor demonstrates a broad temperature response ranging from 200 °C to 1100 °C with negative temperature coefficients (NTC). It exhibits exceptional resistance to high-temperature oxidation and maintains performance stability. Notably, the sensor's resistance changes by 3% after exposure to an 1100 °C air environment for 1 h. This oxidation resistance improvement surpasses the currently reported SiCN precursor thin-film sensors. Additionally, the sensor's temperature coefficient of resistance (TCR) can reach up to -7900 ppm/°C at 200 °C. This strategy is expected to be used for other high-temperature thin-film sensors such as strain gauges, heat flux sensors, and thermocouples. There is great potential for applications in high-temperature field monitoring.

Electrohydrodynamic Printed Ultra-Micro AgNPs Thin Film Temperature Sensors Array for High-Resolution Sensing.

Current methods for thin film sensors preparation include screen printing, inkjet printing, and MEMS (microelectromechanical systems) techniques. However, their limitations in achieving sub-10 μm line widths hinder high-density sensors array fabrication. Electrohydrodynamic (EHD) printing is a promising alternative due to its ability to print multiple materials and multilayer structures with patterned films less than 10 μm width. In this paper, we innovatively proposed a method using only EHD printing to prepare ultra-micro thin film temperature sensors array. The sensitive layer of the four sensors was compactly integrated within an area measuring 450 μm × 450 μm, featuring a line width of less than 10 μm, and a film thickness ranging from 150 nm to 230 nm. The conductive network of silver nanoparticles exhibited a porosity of 0.86%. After a 17 h temperature-resistance test, significant differences in the performance of the four sensors were observed. Sensor 3 showcased relatively superior performance, boasting a fitted linearity of 0.99994 and a TCR of 937.8 ppm/°C within the temperature range of 20 °C to 120 °C. Moreover, after the 17 h test, a resistance change rate of 0.17% was recorded at 20 °C.

Conformal fabrication of functional polymer-derived ceramics thin films

Polymer-derived ceramics (PDCs) is considered to be a promising material for extreme environments such as aero-engine and hypersonic vehicles. However, current methods for PDCs thin films focus on 2D forms, hindering the applications for 3D curved structures where the majority of objects hold complex curvilinear surfaces. To overcome these limitations, a new conformal 3D printing system was developed for in situ preparation of the PDCs films on the curved surfaces for the first time by material extrusion. Through conformal algorithm development and process parameters exploration, different patterns on curved surfaces were realized. Subsequently, a conformal thin film temperature sensor (CTFTS) was fabricated on an alumina cylinder and tested at a high temperature of 800 °C. The results showed that the repeatability of multi-cycles was excellent and the resistance change rate was less than 1 % for half an hour of holding at 400 °C, 600 °C, and 800 °C. Given the high performance of the CTFTS on curved surfaces and the surface compatibility, CTFTS was fabricated conformally on a silicon nitride ceramic bearing and an alumina ceramic bolt, respectively. In the flame test and the rotation test, the CTFTS could detect in situ temperature in real-time with a response better than the commercial thermocouple. Therefore, the PDCs thin film conformal fabrication technique in this study is a highly promising approach for bringing PDCs films to practical applications, as well as a reference for multi-material conformal 3D printing.

Novel lead-connection technology for thin-film temperature sensors with arbitrary electrode lengths

Traditional thin-film thermocouples (TFTCs) have limitations in measuring real surface temperature changes in aircraft because the connection between the nanofilm and the leads can easily fail. Despite this, how to improve this weak connection has rarely been addressed in previous studies. In this study, a lead-embedded alumina ceramic substrate is proposed to improve the durability of TFTCs. Multi-layer two-dimensional nanofilms with different thin-film electrode lengths were prepared on a substrate using DC-pulsed magnetron sputtering. Furthermore, the effect of the thin-film electrode length on the sensitivity, response time and measurement error of the sensor was investigated. The electrode length did not affect the sensitivity and response time; however, as it was increased, the temperature measurement error decreased. In addition, the static and dynamic performance, repeatability, measurement accuracy and service lifetime of the developed sensor were verified. The results show that the sensor has high sensitivity and linearity and good repeatability, with the response time being in microseconds. The sensor can continue to operate at 500 °C for more than 2 h with no signal interruption. The sensor’s reported accuracy is 0.43% at 300 °C.

Thin-film temperature sensor made from polymer-derived ceramics based on laser pyrolysis

Thin-film temperature sensor made from polymer-derived ceramics based on laser pyrolysis

Real-Time Cell Temperature Fluctuation Monitoring System Using Precision Pt Sensors Coated with Low Thermal Capacity, Low Thermal Resistance, and Self-Assembled Multilayer Films.

Real-time monitoring of cell temperature fluctuation can help researchers better understand physiological phenomena and the effects of drug treatment on cells, which is a novel and important tool for cellular informatics. The platinum (Pt) temperature sensor is widely used in temperature measurement with the advantages of strong stability, great accuracy, and high sensitivity. However, the commercially available Pt sensors have large thermal resistance and heat capacity which are difficult to be applied for cell temperature measurement because only a very small amount of heat flux is generated by live cells. In this study, we designed a system using precision Pt thin-film temperature sensors with low heat capacity and thermal resistance. The Pt thin-film sensors are covered by a silicon nitride insulation layer grafted with a self-assembled multilayer silane film for promoting cell adhesion. The temperature coefficient of resistance of the Pt temperature sensor was about 2100 ppm/°C. The four-wire lead design next to the sensor detection area ensured maximum accuracy, resulting in a system noise below 0.01 °C over a long time. HEK-293T and HeLa cells were cultured on the sensor surface, respectively. The temperature fluctuation of 293T cells was monitored in a cell culture medium, showing a temperature increase of about 0.05-0.12 °C. The temperature fluctuation of HeLa cells treated with cisplatin was also measured and recorded, indicating a temperature decrease of 0.01 °C first and then a gradual temperature increase of 0.04 °C. The Pt sensor system we developed demonstrated high sensitivity and long stability for cell temperature fluctuation monitoring, which can be widely used in cell activity and cellular informatics studies.

Preparation and Application of Nanocomposite Thin-Film Temperature Sensor during the Milling Process.

During the titanium alloy milling process, high temperatures in the tool-chip contact area will affect the tool life and precision of titanium alloy machining. Therefore, it is essential to measure the temperature of the tool-chip contact area continuously. In this paper, a finite element simulation model of the milling process was established using ABAQUS2020 to obtain the highest temperature location in the tool-chip contact area when milling titanium alloy. The integration of the wire with the alumina ceramic substrate formed an integrated wire substrate. Furthermore, NiCr, NiSi, and SiO2 films were deposited on the substrate sequentially using the DC pulsed magnetron sputtering technique. Finally, its microscopic morphology and static and dynamic performance were tested. The results show that the developed thin-film thermocouple temperature sensor has a Seebeck coefficient of 40.72 μV/°C and a dynamic response time of 0.703 ms. The application of the sensor to our titanium alloy milling experiments showed that the sensor can monitor the transient temperature in the tool-chip contact area, and its temperature measurement performance showed no detrimental effect from wearing. The effect of each milling parameter on the milling temperature was analyzed using ANOVA, and a regression model with an R-sq of 96.76% was obtained for the milling temperature.

A Light Shield Temperature Sensor for a Display Backplane

Liquid Crystal Display (LCD) and Organic Light Emitting Diode (OLED) display are operated by voltage or current driving. Several types of Thin-Film Transistor (TFT) are used in the backplane of a display, LTPS and a-IGZO TFTs are those. As the applied voltage increases to increase the brightness of the display, heat generation also increases at the channel of the TFT. Such heat generation increase the temperature, which degrades the characteristics of the TFT, and decrease the lifetime of the organic device. Therefore, in order to keep the quality of the display, it is necessary to monitor the temperature of the display and control related signals to implement optimal image quality. There are various temperature sensors which can be used to detect such a temperature change in a display. In the case of using a discrete temperature sensor, the process and cost are increased by attaching the temperature sensor additionally. However, in the case of a temperature sensor integrated into the display, an process for the temperature sensor is not necessary. One way to integrate is using resistance changing material with a reference resistor outside. In this case, temperature accuracy can be reduced when the reference resistance changes due to the influence of the external temperature. To solve the problem, external reference resistance is removed in this proposed sensor scheme. Figure 1 shows the developed thin-film temperature sensor, which consists of two wires connected in series. The temperature coefficients of Molybdenum (Mo) and Indium Tin Oxide (ITO) are different from each other, and that of ITO is about 1.2 times or more than that of Mo. In this scheme, no external resistance is required. In addition, to reduce the process steps, a thin film temperature sensor is designed to replace a light shield layer which is formed at the bottom of the active layer to prevent the input of light. The two thin film materials are connected in series and the voltages at a connecting point are measured. The generated heat transferred to the temperature sensor was tested for repeatability and accuracy. The thin-film temperature sensor was designed to be located at the bottom of a-IGZO Top Gate TFT structure to check the heating during the operation of TFT. an interlayer insulation film was deposited on the temperature sensor before deposition of the active layer. The temperature of the TFT was measured by a temperature sensor Figure 1. shows the schematic cross-sectional structure of the developed oxide TFT with an integrated temperature sensor. Figure 1

MEMS-based Pt film temperature sensor chip on silicon substrate

The thin film temperature sensor chip is fabricated with the Ti/Pt film layer on a silicon substrate by micro electromechanical systems technology. Using electron beam evaporation, 10 and 100 nm thick Ti/Pt films layers are fabricated. Then, the annealing experiments for the temperature sensor chip are carried out in air and vacuum at 400 °C–800 °C. The relationship between the resistance of temperature sensor chip and tested temperature in the range of −30 °C–150 °C is studied based on different annealing conditions, and its electrical characteristic parameters are evaluated including temperature coefficient of resistance (TCR), hysteresis and measuring precision. At the same time, the morphology and grain size of the Pt film layer are studied by x-ray diffractometer, atomic force microscope and scanning electron microscope. The changes of square resistance and internal stress are tested by four probes and stress analyser to analyze the performance of the temperature sensor chip. The testing experiments show that the electrical properties of the temperature sensor chip annealed in air are better than those in vacuum. Finally, the temperature sensor chip is fabricated with the optimal performance with the annealing temperature of 800 °C for 30 min in air. Compared with before annealing, TCR increased by 75.4% from 1790 to 3140 ppm K−1, hysteresis reached 0.2% FS and precision reached 0.32% FS.

Tunable sensitivity of zirconium oxynitride thin-film temperature sensor modulated by film thickness

Tunable sensitivity of zirconium oxynitride thin-film temperature sensor modulated by film thickness

Thin-film temperature sensor made from particle-filled polymer-derived ceramics pyrolyzed in vacuum

Thin-film sensors have wide applications in the fields of high-temperature measurement, such as in the hot section of aero engines. Polymer-derived ceramics (PDCs) are diversified, ease to shape, and resistant to thermal shock. However, they are seldom used as sensitive parts of thin-film sensors due to the oxidation of PDC thin films. To solve this challenging problem, pyrolysis of PDC thin films in vacuum is proposed in this work, and the anti-oxidation performances are verified in a high-temperature sensor based on such a PDC thin film. The temperature measurement experiment shows that the PDC thin-film temperature sensor with thickness of about 10 µm pyrolyzed in vacuum can measure temperature from room temperature to 800 ℃, which provides a feasible way for fabrication of high-temperature PDC thin-film sensors such as heat flux sensors and strain sensors.

Transparent, Breathable Temperature and Humidity Sensor using Ion Gel and Polymer Thin Films

In this study, a transparent and highly breathable thin-film temperature and humidity sensor was developed as a concept proof for multimodal patchable devices using ion gels. The sensor can detect temperature and humidity selectively by using two types of ionic liquids for sensing layers. Ionic liquids were compatibilized with polymers to form a semi-solid state, called ion gels. Polydimethylsiloxane (PDMS) thin film was used for substrates. Carbon nanotube (CNT) transparent electrodes were fabricated onto PDMS substrate by spray coating method. Ion gel sensing layers were also spray-coated onto CNT electrodes. The fabricated sensor exhibited more than 80 % visible light transmittance and 3.9 times higher water vapor transmission than skin evaporation. LCR meter was used for measuring the impedance of temperature and humidity sensors. As a result, selective detection of temperature and humidity was achieved by using two types of ion gels with different hydrophilicity. These results suggest the easy fabrication of multimodal patchable devices by using various types of ionic liquids.

Aerosol jet printing of nickel oxide nanoparticle ink with ultraviolet radiation curing for thin-film temperature sensors

In this study, the ultraviolet (UV) radiation curing process and furnace curing process for curing aerosol jet printed nickel oxide (NiO) nanoparticle thin films were investigated. NiO has a negative temperature coefficient and can be used to fabricate temperature sensors. Four UV power settings (for 10 min) and four furnace temperatures (for 1 h) were used to cure the aerosol jet printed sensors. The resultant sensor resistance at 100 °C and 180 °C was measured, and the sensor’s sensitivity was characterized by a B value. Confocal microscopy was performed to characterize the sensor surface. The 60% UV power setting yields the lowest resistance and the highest B value among all sensors. The analysis of variations shows that the UV power setting is not a significant factor in the resistance and B value, while the furnace temperature is a significant factor. This indicates that UV curing is a more robust method and does not need to be optimized to achieve good results. The UV curing process not only reduces the required curing time but also improves the performance of the temperature sensor.

Polymer-derived ceramic thin-film temperature sensor

In-situ monitoring of machines in harsh environment remains challenging due to lack of high-performance sensors. Most of sensors cannot survive over 600 ℃ even with packaging. In this work, an ultra-thin-film temperature sensor was fabricated based on polymer-derived ceramics (PDCs) via direct-writing for aerospace applications. The sensitive film with thickness of 10 µm consists of polymer-derived SiCN filled with TiB2, ZrB2 and SiC nano-particles. The resistance-temperature dependence tests of the sensor indicates that the resistance of the PDC thin film decreases monotonically with rising temperature and exhibits good repeatability at temperatures from room temperature to 800 ℃ in the air environment. The fabricated thin-film sensor shows great potential for high temperature applications and the technological routine provides a feasible pathway for structure/function integration in aerospace manufacture.

A thin-film temperature sensor based on a flexible electrode and substrate

Accurate temperature measurements can efficiently solve numerous critical problems and provide key information. Herein, a flexible micro-three-dimensional sensor, with a combination of platinum and indium oxide to form thermocouples, is designed and fabricated by a microfabrication process to achieve in situ real-time temperature measurements. The stability and reliability of the sensor are greatly improved by optimizing the process parameters, structural design, and preparation methods. A novel micro-three-dimensional structure with better malleability is designed, which also takes advantage of the fast response of a two-dimensional thin film. The as-obtained flexible temperature sensor with excellent stability and reliability is expected to greatly contribute to the development of essential components in various emerging research fields, including bio-robot and healthcare systems. The model of the application sensor in a mask is further proposed and designed to realize the collection of health information, reducing the number of deaths caused by the lack of timely detection and treatment of patients.