Thermal Sensor Applications Research Articles

Manganese Oxide Applications in Sulfonamides Electrochemical, Thermal and Optical Sensors: A Short Review

AbstractIn recent years, the development of highly sensitive and selective electrochemical sensors has been a pivotal area of research, driven by the growing demand for environmental monitoring and industrial process control. Among various materials investigated for sensor applications, manganese oxide (MnO2) nanoparticles have garnered significant attention due to their excellent electrochemical properties, environmental friendliness, and natural abundance. Critical analyses of the synthesis of MnO2 using different techniques such as hydrothermal method, chemical precipitation, and sol–gel process which allows for the fine-tuning of particle size and morphology while enhancing the electrochemical sensing capabilities have been reviewed. The review also provides a comprehensive overview of the recent advancement evaluation of manganese oxide-based electrodes for detecting sulfonamides and other analytes in water across diverse matrices. This paper sets the stage for a comprehensive exploration of the synthesis methods and application areas of MnO2 nanoparticles in electrochemical sensors, highlighting their role in advancing sensor technology and their impact on various sectors. Graphical Abstract

Water-based metamaterial absorber for temperature modulation

In this study, a transmissive all-dielectric metamaterial absorber comprising a photosensitive resin and water layers was proposed. The water layers comprised coin rings, crosses, and fan shapes. The as-obtained absorber achieved >90% absorption of electromagnetic waves within the frequency range of 18.4–41.7 GHz, and the absorption bandwidth covered the Ka-band. Because of the symmetric structure of the designed metamaterial, it was not influenced by polarization. The inherent dispersive properties of water result in a dielectric constant that varies significantly with temperature. This led to fluctuations in the absorption efficiency of the designed metamaterial to different degrees with changes in temperature. The analysis of electric and magnetic fields distributions revealed that the primary absorption physical mechanism of the designed metamaterial originated from magnetic resonances in the water layers. The proposed transmissive metamaterial absorber has potential applications in high-sensitivity thermal and temperature sensors.

Structural design and performance optimization of Co/Bi0.5Sb1.5Te3 artificially tilted multilayer thermoelectric devices

Due to the complex principle of transverse thermoelectric conversion and the specific preparation technique, there are few studies on the three-dimensional structure of artificially tilted multilayer thermoelectric devices (ATMTDs), which also lags the development of ATMTDs for applications. It is necessary to optimize the three-dimensional structure of ATMTDs to satisfy the requirements of practical applications in thermal sensors, power generation, refrigeration, and so on. In this paper, Co/Bi0.5Sb1.5Te3 ATMTDs are selected as the research object. A COMSOL Multiphysics simulation analysis and experimental validation are used to establish the relationship between the structure and its thermal sensing, power generation, and cooling performance. Results indicate that increasing the length significantly improves the thermal response voltage. Increasing the length and width enhances output power while increasing the height of the ATMTD improves the thermoelectric conversion efficiency. The effective cooling temperature improves when the heat transfer area decreases or the height increases. Based on these findings, flexible thin-film thermal sensors, high-efficiency waste heat power generation tubular devices, and high-efficiency refrigeration pyramidal devices are designed. The results will lead to effective optimization and promote the multi-field application of ATMTDs.

Significance of quadratic radiation and variable thermal conductivity on heat transfer of hybrid nanofluid using Xue model: A Legendre wavelet approach

Carbon nanotubes have a broad spectrum of applications in thermal management, enhanced cooling, lubricants, sensors and detections, environmental remediation, biomedical, and drug delivery. Motivated by its industrial applications, this work analyses the effects of nonuniform heat source/sink and quadratic thermal radiation on the thermal characteristics of hybrid nanofluid flow over a curved stretching sheet using the Legendre wavelet collocation technique (LWCT). The base fluid is found to be composed of ethylene glycol and water in the ratio of 30:70, and the nanoparticles are taken as single-wall carbon nanotube (SWCNT) and multi-wall carbon nanotube (MWCNT) in the ratio of 2% each. The thermal conductivity models, namely Xue, modified Maxwell and Hamilton-Crosser, are compared for heat transfer enhancement. From the results up to 5% volume fraction, the Xue model shows the maximum rate of heat transfer enhancement, while the above 5% Hamilton-Crosser model shows the maximum rate of heat transfer enhancement. The temperature profiles of existing hybrid nanofluid are increased with a heat source, radiation and variable thermal conductivity. Moreover, the graphs describing the local Nusselt number display the heat transfer rate depreciation with an increase in variable thermal conductivity and radiation parameters.

Doped CeO2/water nanofluids analyzed the performance of thermal conductivity and heat transfer: An experimental and theoretical investigations

A combined experimental and theoretical study on thermal conductivity, heat transfer specific heat, and electronic properties has been done for doped CeO2/water nanofluid. First, the sol-gel method was implemented for the synthesis of doped CeO2 nanoparticles and then a mixture of nanoparticles with different concentrations of nanofluid. X-ray diffraction and SEM analysis confirm the structural phase purity and homogeneous mixing of nanofluids. Experimental thermal conductivity and specific heat of pure and 4f-doped CeO2 were estimated and found very close to our theoretical calculations. Experimental investigations have been carried out for the measurement of heat transfer using pure and doped CeO2/water nanofluid as the coolant. The experiments were aimed at determining the heat transfer and other thermal properties with different concentrations and with various fluid with Reynolds number 2500 and 3500. The heat transfer coefficient of nanofluids increases not only with an increase in the volume flow rate of the hot water but also increases with increase in the atomic number of dopant elements in CeO2. Electronic states show variation in band gap with doping which may also play an important role in the improvement of solar collectors. It is clear from experimental and theoretical findings that the thermal and electronic properties depend on number of valance electrons. Hence doping of 4f-element in CeO2 plays a vital role to increase the thermal conductivity and tuning of electronic properties leads to many applications in thermal sensors and solar cell-based industries.

A Review of Sensor Applications in Electric Vehicle Thermal Management Systems

With the rapid development of the automotive industry, the application of sensors is of great importance in maintaining the reliability of electric vehicles and ensuring the safe operation of electric vehicles. Faced with the increasing data of thermal management system condition monitoring, sensor detection is widely used in the monitoring of electric vehicle thermal management system. In recent years, a large number of related studies and contributions to the literature have been published. Although a number of reviews have summarized this, these reviews lack an overview of the issues and methods raised in these studies. This paper reviews recent sensor applications for electric vehicle thermal management systems. Currently, battery internal sensors, battery external sensors and related multi-sensor fusion, traditional motor sensors, positionless motor sensors, and component-level sensors of air conditioning systems are the main application sensors in the field of thermal management systems. This article introduces the basic principles of each type of sensor, reviews the relevant applications of various thermal management modules, and summarizes the usage characteristics of each type of sensor. The main problems faced by the existing research on the application of thermal management system-based sensors, such as the detection accuracy of traditional sensors and the detection stability of advanced sensors, are summarized, and the solutions proposed by the existing research are also summarized. Finally, some future research directions, trends, and hotspots are outlined. It is hoped that this review can help readers to understand the problems and existing solutions for thermal-management-system-based sensor applications, and to conduct related research more effectively.

Cross-linked Polyimide Nanofibrous Aerogels with Hierarchical Cellular Structure for Thermal Insulation

Due to their low bulk density, high porosity, and functional performance, aerogels are ideal candidates for a variety of applications. However, their potential application in a variety of fields is limited by their time-consuming and costly complex fabrication process. In this study, electrospun 3-aminopropyltriethoxysilane-grafted polyimide (PI@APTES) nanofibers were used to construct nanofibrous aerogels (NFAs) via freeze-drying a dispersion of cross-linked-PI short fibers and a binder (PI@APTES), resulting in improved properties and functionalities. A highly siloxane cross-linked network structure was formed by hydrolysis and condensation reactions to generate stable nanofibrous aerogels. The obtained polyimide nanofibrous aerogels (PiNFAs) had a hierarchically three-dimensional (3D) microporous structure, high porosity (over 98%), tunable densities (10.6 ± 0.7–13.6 ± 0.2 mg cm–3), solvent resistance, superhydrophobicity (water contact angle over 163°), low thermal conductivity (as low as 33.2 mW m–1 K–1), and mechanical stability. These PiNFAs are promising candidates for potential applications in thermal insulation, lightweight construction, filtration, and sensors.

Research on Dust Effect for MEMS Thermal Wind Sensors

This communication investigated the dust effect on microelectromechanical system (MEMS) thermal wind sensors, with an aim to evaluate performance in practical applications. An equivalent circuit was established to analyze the temperature gradient influenced by dust accumulation on the sensor’s surface. The finite element method (FEM) simulation was carried out to verify the proposed model using COMSOL Multiphysics software. In experiments, dust was accumulated on the sensor’s surface by two different methods. The measured results indicated that the output voltage for the sensor with dust on its surface was a little smaller than that of the sensor without dust at the same wind speed, which can degrade the measurement sensitivity and accuracy. Compared to the sensor without dust, the average voltage was reduced by about 1.91% and 3.75% when the dustiness was 0.04 g/mL and 0.12 g/mL, respectively. The results can provide a reference for the actual application of thermal wind sensors in harsh environments.

Where should the thermal image sensor of a smart A/C look?-Occupant thermal sensation model based on thermal imaging data

Applying thermal imaging sensor to air conditioner for monitoring human thermal sensation and achieving dynamic settings may satisfy occupants' thermal needs while saving energy. The existing studies are mostly based on single-view imaging to build the model and ignore the possible differences in body surface temperature on thermal sensation response by gender, etc., which may have many limitations. Subject experiments were conducted in an artificial climate chamber to obtain subjective questionnaires and thermal images of the exposed frontal face, lateral face, top of the head, forearm, and hand dorsum of 27 subjects in this study. By applying machine learning classification algorithms and global optimal regression algorithms, the temperature collection zones that can accurately reflect the thermal sensation of both genders in each view were analyzed, and a two-stage thermal sensation assessment model applicable to multiple views was developed. Of the various imaging views, the frontal view of the face is the best, followed by the lateral view of the face, the top view of the head, and the forearm/hand dorsum view. For male and female, the mean absolute errors of the thermal sensation assessment model established were 0.41–0.49 and 0.50–0.53 thermal sensation units. In addition, gender differences were found in the response of head surface temperatures to thermal sensation. The results obtained can provide a reference for the application of thermal image sensor to smart air conditioners.

Flow Characteristics and Switching Mechanism of Bistable Slit Flow Actuated by Temperature.

The bistable flow is attractive as it can be analogous to a switch to realize flow control. Based on the previous studies on actuation technique, the present study first proposed temperature-driven switching of bistable slit flow. A two-dimensional numerical simulation was conducted to investigate the flow deflection characteristics and switching mechanism. It was concluded that the temperature gradient not only biases the slit flow but also locks it to the high-temperature side. The flow deflection angle became larger with the increase in temperature gradient. Being driven by the temperature, the flow can be switched from one side to the other. Furthermore, the fluid viscosity, which varies with temperature, determines the degree of flow deflection and the entire switching time. This research can enrich the active regulation of flow and has significant potential applications in thermal sensors, thermal detectors, microelectromechanical systems, biomedicine, and other equivalent fields.

Thermal sensing capability and current–voltage–temperature characteristics in Pt/n-GaP/Al/Ti Schottky diodes

We have discussed the thermal sensing capability under a constant current level and current versus voltage (I–V) traces by measuring the temperature of high series resistance Pt/n-GaP/Al/Ti Schottky structures in the 100−320 K range. The Rs values of 35 Ω and 4.50 × 103 kΩ for the device have been determined from I–V traces at 320 and 100 K, respectively. The thermal sensing (V–T) curves are expected to give a straight line at each current level. However, the V–T curves have deviated upward from linearity due to the high Rs value of the device after a certain temperature. The deviation point from linearity in V–T traces shifts to higher temperatures with an increase in bias voltage and current level. Thereby, the straight-line interval portion of the V–T curve has become too small with an increase in the current value. The thermal sensing coefficient α changed from 2.49 mV/K at 10 μA to 3.21 mV/K at 0.50 nA. Therefore, it has been concluded that the Pt/n-GaP/Al/Ti Schottky barrier (SB) is preferable for thermal sensor applications at the small current levels of 0.50, 1.0, 2.0, and 10.0 nA with high sensitivity up to a minimum temperature of 100 K. From I–V curves, qΦb0 and ideality factor values have ranged from 1.200 eV and 1.066 at 320 K to 0.854 eV and 1.705 at 100 K. It has been reported in the literature that the large SB height leads to a better temperature response.

Epitaxial Grown VO2 with Suppressed Hysteresis and Low Room Temperature Resistivity for High-Performance Thermal Sensor Applications

The ability of VO2 to undergo semiconductor-to-metal phase transition (SMT) upon heating makes it a very attractive material for uncooled bolometers. The SMT of VO2 represents a large temperature coefficient of resistance, which is an important parameter for the development of highly responsive microbolometers. However, other characteristics of the SMT of VO2 such as its high transition temperature (341.2 K), the sharpness of the transition, its hysteresis, and the high room temperature resistivity limit the performance of this material in microbolometers. In this work, we grow a high-quality epitaxial ultrathin film VO2 on c-plane Al2O3 by pulsed laser deposition. The low deposition temperature and tuning the oxygen partial pressure during the growth process enable control over the grain size and oxygen vacancy concentration. This allowed controlling the SMT parameters of the samples. In particular, we show that the high density of grain boundaries associated with nanosized grains suppresses the thermal hysteresis of the SMT. Simultaneous control over the density of oxygen vacancies and the size of grains enables the adjustment of the temperature coefficient of resistance, room temperature resistivity, SMT temperature, sharpness, and thermal hysteresis toward suitable values for the fabrication of efficient VO2-based uncooled bolometers. Compared with other VO2 fabrication methods, this approach can be viewed as a simpler alternative for VO2 fabrication with favorable properties for practical bolometer applications.

Multifunctional optical thermometry using dual-mode green emission of CaZrO3:Er/Yb/Mo perovskite phosphors.

The weak emission intensity of rare-earth element-doped dual-mode materials leads to low-sensor sensitivity, which is a challenge in optical sensor applications. The present work achieved high-sensor sensitivity and high green color purity based on the intense green dual-mode emission of Er/Yb/Mo-doped CaZrO3 perovskite phosphors. Their structure, morphology, luminescent properties, and optical temperature sensing properties have been investigated in detail. Phosphor shows a uniform cubic morphology with an average size of approximately 1 μm. Rietveld refinement confirms the formation of single-phase orthorhombic CaZrO3. Under the excitation of 975 and 379 nm, the phosphor emits pure green up and down-conversion (UC and DC) emission at 525/546 nm corresponding to 2H11/2/4S3/2-4I15/2 transitions of Er3+ ions, respectively. Intense green UC emissions were achieved because of energy transfer (ET) from the high-energy excited state of Yb3+-MoO42- dimer to the 4F7/2 level of Er3+ ion. Furthermore, the decay kinetics of all obtained phosphors confirmed ET efficiency from Yb3+-MoO42- dimer to Er3+ ions, leading to strong green DC emission. Moreover, the DC of the obtained phosphor shows that a sensor sensitivity value of 0.697% K-1 at 303 K is higher than the UC (0.667% K-1 at 313 K) because the thermal effect generated by the DC excitation source light is ignored compared with UC luminescence. CaZrO3:Er-Yb-Mo phosphor shows intense green dual-mode emission with high green color purity, 96.50% of DC and 98% of UC emissions, and high sensitivity, making it suitable for optoelectronic devices and thermal sensor applications.

A longitudinal study of the occupancy patterns of a university library building using thermal imaging analysis

ABSTRACT Current debates around the ‘performance gap’ have highlighted the need to study building occupancy patterns to improve design solutions and better understand space utilisation. However, capturing occupancy data is resource intensive. There is a need for solutions that gather real-time occupancy data while maintaining the users’ privacy. In response to this challenge, this paper discusses applying a thermal imaging-based method for measuring occupancy in buildings and generating behavioural insights. A longitudinal analysis of the occupancy patterns over a full academic year is conducted for a university library building in the UK. The granular data collected through the thermal imaging analysis reveal insights into the building’s occupancy patterns over academic terms and vacation periods. The findings debunk conventional conceptions of library use during weekends/weekdays and terms/vacations. The application of thermal imaging sensors to monitor occupancy within the library building suggests the potential use of real-time data to improve the library’s space and organisational management. The paper makes a case for having an occupancy monitoring strategy in place that corresponds to the data needed for making effective interventions.

Thermotropic Optical Response of Silicone-Paraffin Flexible Blends.

Organic phase change materials, e.g., paraffins, are attracting increasing attention in thermal energy storage (TES) and thermal management applications. However, they also manifest interesting optical properties such as thermotropism, as they can switch from optically opaque to transparent reversibly and promptly at the melting temperature. This work aims at exploiting this feature to produce flexible silicone-based blends with thermotropic properties for applications in glazed windows or thermal sensors. Blends are produced by adding paraffin (Tm = 44 °C, up to 10 phr) to a silicone bicomponent mixture, and, for the first time, cetyltrimethylammonium bromide (CTAB) is also added to promote paraffin dispersion and avoid its exudation. CTAB is proven effective in preventing paraffin exudation both in the solid and in the liquid state when added in a fraction above 3 phr with respect to paraffin. Rheological results show that paraffin decreases the complex viscosity, but neither paraffin nor CTAB modifies the curing behavior of silicone, which indicates uniform processability across the investigated compositions. On the other hand, paraffin causes a decrease in the stress and strain at break at 60 °C, and this effect is amplified by CTAB, which acts as a defect and stress concentrator. Conversely, at room temperature, solid paraffin only slightly impairs the mechanical properties, while CTAB increases both the elastic modulus and tensile strength, as also highlighted with ANOVA. Finally, optical transmittance results suggest that the maximum transmittance difference below and above the melting temperature (65-70 percentage points) is reached for paraffin amounts of 3 to 5 phr and a CTAB amount of max. 0.15 phr.

Coupling of Epsilon-Near-Zero Mode to Mushroom-Type Metamaterial for Optimizing Infrared Suppression and Radiative Cooling

We report a complementary metal oxide semiconductor (CMOS) compatible metamaterial-based spectrally selective absorber/emitter (MBSSAE) for infrared (IR) stealth, which has the low absorption/emissivity in the IR atmospheric transmission window (3 µm–5 µm, 8 µm–14 µm) and ultra-high and broadband absorption/emissivity in the IR non-atmospheric window (5 µm–8 µm). We propose a novel method for the broadband absorption/emissivity in 5 µm–8 µm with incorporation of an epsilon-near-zero (ENZ) material between the top patterned aluminum (Al) disks layer and the silicon oxide (SiO2) spacer layer. With an appropriate design, the peaks in the IR atmospheric transmission window can be suppressed while the peak intensity in the non-atmospheric window remains high. The optimized MBSSAE has an average absorption/emissivity less than 10% in 8 µm–14 µm and less than 6% in 3 µm–5 µm. And the average absorption/emissivity in 5 µm–8 µm is approximately over 64%. This proposed scheme may introduce the opportunities for the large-area and low-cost infrared stealth coating, as well as for the radiative cooling, spectral selective thermal detector, optical sensor, and thermophotovoltaic applications.

Enhancement of mechanical, thermal and optical properties of TiO2 thin films using glancing angle deposition technique

RF Magnetron sputtering has been used to compare the mechanical, thermal, and electrical characteristics of titanium oxide (TiO2) thin films. The Glancing Angle Deposition methods (GLAD) have been implemented during the deposition of a thin film of TiO2. After annealing thin films on an ITO substrate, X-RD indicates the anatase phase, and SEM investigation confirms the deposition of TiO2 thin films and their surface morphology. The mechanical, thermal, and electrical properties of TiO2 thin films prepared by magnetron sputtering with RF supply have been investigated. Using GLAD deposition, a clear change in thermal conductivity and elastic properties has been observed. Experimental specific heat of thin film deposited at zero angles follows Debye and Einstein equation, while with GLAD deposition specific heat shows an increase in deviation as the angle of deposition increases. With a rise in inclination angle, a clear change in transmission spectra towards a higher wavelength has been observed. Following heat treatment, the optical transmission spectra of thin films with GLAD deposition confirm the formation of fringes and have been shifted towards the higher wavelength side to increase in inclination. Hence, using GLAD deposition on TiO2 plays an important role to change thermal conductivity, specific heat, elastic and electronic properties and which leads to many applications in thermal solar collectors, thermal sensors, thermo-optical switching, and sensing-based industries.

Efficient system-level simulations of thermal wind sensors considering environmental factors

For the development of micro-electro-mechanical system (MEMS) technology during the past several years, MEMS design has requirements of high precision, high efficiency, iterative design, joint design of structure and circuit and so on. With the improvement of thermal wind sensor performance requirements and the complexity of the application environment, it is becoming increasingly difficult to ignore the impact of environmental factors. However, there is no system-level model considering the influence of environmental factors adequately in macro model. To solve these problems, a 2D thermal wind sensor macro model considering environmental factors is proposed. In order to build a macro model which can reflect the output of sensors in different environments, this paper, starting from the basic law of heat transfer, proposes an accurate macro model of the thermal wind sensor. The model proposed in this study accurately considers the influence of thermal and transport properties in different environments, and can be simulated together with the interface circuits in Cadence software. The results indicate that the variation of temperature and atmospheric pressure in the natural range can affect the sensor output by more than 15%, and the influence of relative humidity should not be ignored when the temperature is higher than 70 °C. Furthermore, the flow direction over the sensor can be further studied according to the 2D equivalent circuit model. The simulation results agree well with the experimental results, and the results can provide a valuable reference for the research and practical application of thermal wind sensors.

Intense green upconversion emission of rare-earth-doped Sr3(PO4)2/Sr2P2O7 powder: Effect of annealing temperature and temperature-sensor properties

A series of Mo6+-doped Sr3(PO4)2/Sr2P2O7: Er3+-Yb3+ was synthesized by coprecipitation followed by heat treatment. X-ray diffraction and scanning electron microscopy analyses confirmed that the annealing temperature strongly influenced the morphology and structure of the material. Under laser-diode excitation wavelength of 975 nm, the green and red upconversion emission intensity as a function of annealing temperature reached its maximum value at 1000℃. The green emission intensity of the 3 mol% Mo6+-doped sample sharply increased, becoming about ~143 times higher than that of the undoped samples. Furthermore, the obtained phosphor presented a high temperature sensitivity of Sa and Sr with a maximum value of 1.05% K−1 at 363K and 0.8% K−1 at 303K, respectively. These results indicated that the Sr3(PO4)2/Sr2P2O7: Er−Yb−Mo phosphor was an efficient upconversion luminescent material suitable for thermal-sensor applications. The selection and control of annealing temperature played a key role in the success of the synthesis and acquisition of the phosphor’s desired physical property. Finally, several explorations in this work that enhanced UC luminescence by using the transition-metal ion Mo6+ provided a novel idea to design strong UC emission biomaterials for their medical applications.

Light-Induced Reactions within Poly(4-vinyl pyridine)/Pyridine Gels: The 1,6-Polyazaacetylene Oligomers Formation.

Cyclic 6-membered aromatic compounds such as benzene and azabenzenes (pyridine, pyridazine, and pyrazine) are known to be light-sensitive, affording, in particular, the Dewar benzene type of intermediates. Pyridine is known to provide the only Dewar pyridine intermediate that undergoes reversible ring-opening. We found that irradiation of photosensitive gels prepared from poly(4-vinyl pyridine) and pyridine at 254 or 312 nm leads to pyridine ring-opening and subsequent formation of 5-amino-2,4-pentadienals. We show that this light-induced process is only partially reversible, and that the photogenerated aminoaldehyde and aminoaldehyde-pending groups undergo self-condensation to produce cross-linked, conjugated oligomers that absorb light in the visible spectrum up to the near-infrared range. Such a sequence of chemical reactions results in the formation of gel with two distinct morphologies: spheres and fiber-like matrices. To gain deeper insight into this process, we prepared poly(4-vinyl pyridine) with low molecular weight (about 2000 g/mol) and monitored the respective changes in absorption, fluorescence, 1H-NMR spectra, and electrical conductivity. The conductivity of the polymer gel upon irradiation changes from ionic to electronic, indicative of a conjugated molecular wire behavior. Quantum mechanical calculations confirmed the feasibility of the proposed polycondensation process. This new polyacetylene analog has potential in thermal energy-harvesting and sensor applications.