Calorimetry has been used to detect heat changes in biomedical diagnostics and chemical reaction monitoring. Application of calorimetry to micro/nano scale biological samples, however, is constrained by insufficient sensitivity and resolution for weak thermal effects. This work presents a novel microfluidic calorimeter for thermal detection in biochemical reactions. The microcalorimeter integrates 0.3 μL polydimethylsiloxane (PDMS) chambers and a Bi2Te3-Sb2Te3 thermopile on a polyimide (PI) substrate, minimizing reagent consumption while achieving a sensitivity of 8.05 V/W and a resolution of 11.58 nW. The microfluidic calorimeter demonstrates excellent performance in quantifying exothermic reactions from ethanol dilution and glucose oxidation. The glucose concentration is proportional to the integrated area under the time-resolved calorimeter’s response curve. Additionally, specific detection of rabbit immunoglobulin G (IgG) is realized by monitoring the antibody-antigen binding reaction. These results illustrate the potential of the novel microcalorimeter in biomolecular detection, offering a promising system for biomedical diagnostics and monitoring.

Current thin-film thermopile sensors for photothermal detection typically utilize lateral structures, resulting in relatively slow response times, particularly for high-density heat fluxes, which limits the accuracy of transient and high-frequency signals. In this work, we present a fast-response micro thermoelectric device (& micro;-TED) featuring a micro cross-plane thermopile and an enhanced resonant absorber. The device exhibits an ultra-high thermocouple density of 19,900 TCs/cm2, achieved through an optimized MEMS-based fabrication process. Experimental results demonstrate a linear output voltage range from 260 kW/m2 to 1 MW/m2, with a sensitivity of approximately 1.37 & micro;V/(W/m2). Additionally, the suspended top connection is functionalized as a resonant absorption cavity by depositing a nano-thick layer of Bi2Te3, resulting in a significantly reduced heat capacity on the hot side and enhancing the transient performance of the & micro;-TED. As a result, the & micro;-TED achieves a response time of 550 & micro;s and a recovery time of 650 & micro;s. Furthermore, a multi-channel & micro;-TED successfully detected a 50 & micro;m spacing energy difference of the high-power laser, demonstrating the superior resistance of the cross-plane thermopile to thermal interference. The above study not only enhances the potential of thermoelectric devices for rapid response applications, but also unveils a promising prospect for detecting high-energy thermal distribution.

Real-time monitoring of surface heat flux in high-temperature and temperature-changing environments is gaining significant attention for various promising applications, including aero engines, gas turbines, and nuclear power plants. However, the survivability of most current thin-film heat flux sensors above 1200 degrees C still faces challenges. Here, we designed and fabricated a ceramic thin-film thermopile heat flux sensor on an alumina ceramic substrate by physical vapor deposition (PVD). The ITO-In2O3 was chosen as the sensitive layer, while a multilayered YSZ-Al2O3/Al2O3 ceramic film was used as the protective layer to enhance high-temperature stability. Meanwhile, the microstructure and electrical properties of the sensitive films were investigated under different annealing conditions. The results indicate that the sensitive films have a stable structure and good electrical conductivity. The heat flux sensor reaches a sensitivity of 73.4 mu V/(kW/m2) and can measure heat flux up to 1.06 MW/m2. Interestingly, the sensor has excellent high-temperature survivability, and can withstand temperatures up to 1250 degrees C in the ambient atmosphere. Moreover, the application tests were conducted to simulate engine environments, such as flame combustion, shock resistance. These results also indicate that the fabricated sensor shows great potential for actual working applications.

Micro thermoelectric device (μ-TED) emerges with great attention in energy generation, thermal management, and heat sensing applications. However, the large sensitive area is necessary to accommodate enough thermoelectric couples (TCs) for a high thermoelectric performance. This limits the potential in micro energy harvesting and ultra-sensitive sensing applications. Here, we adopted an optimized MEMS-based process to fabricate the ultra-sensitive micro-thermoelectric device (μ-TED). With the help of MEMS-compatible electrochemical deposition, the small size (25 μm), high aspect ratio (1:1.25), and alternating distributed P/N structures are achieved. As a result, the μ-TED realizes an ultra-high integration density of 19,900 thermoelectric couples per cm2. Moreover, it shows a great thermoelectric sensitivity of 212 mV/(K·cm2) and a competitive power factor of 0.51 μW/(K2·cm2), which means the μ-TED is competent for miniaturized applications. Additionally, the μ-TED shows an ultra-low detection limit of 5 mm/s and a short response time of 100 ms, revealing great potential in fast detections of the ultra-low airflow. Furthermore, the ultra-sensitive μ-TED is utilized as a flexible breath sensor, due to its compact size. The breath signal of different motion states is successfully detected. These results confirm that the ultra-sensitive μ-TED holds outstanding potential for ultra-sensitive airflow sensing and energy harvesting devices.

Palladium-chromium (PdCr) is one of the commonly used sensitive materials for high-temperature strain sensors. However, it is prone to oxidation in high-temperature environments, which affects its stability. Therefore, protective layers are typically employed to mitigate the oxidation of the sensitive layer. This work innovatively proposes an in-situ grown oxide film approach to enhance the stability of PdCr thin-film strain gauges (TFSGs) under high-temperature environments. PdCr thin films were sputter-coated with Cr layers of varying thicknesses (1L, 2L, and 3L) and subsequently oxidized for 3 h, 5 h, and 8 h. Microstructural characterization was conducted to evaluate the protective performance of the oxide layers formed under different conditions. The experimental results indicate that a Cr thickness of 3L, oxidized in an oxygen atmosphere for 5 h, provides optimal protection. Based on this parameter, the PdCr TFSGs were fabricated and tested. The results demonstrate that the sensor achieves a minimum temperature coefficient of resistance (TCR) of 151.78 ppm/degrees C, a drift rate (DR) of 0.0002/h and a gauge factor (GF) of 1.739 at 800 degrees C, outperforming previously reported results in the literature. These findings provide valuable insights for the further development of strain sensors.

High-temperature thin-film strain gauges (HTFSGs) hold significant potential for monitoring extreme environments in fields such as aerospace, nuclear energy, and automotive engineering. With advances in materials science, HTFSGs based on ceramics, metals, and composite materials have progressively achieved high-precision strain measurements in high-temperature environments. In recent years, substantial progress has been made in areas such as material selection, sensor structural optimization, high-temperature oxidation resistance, and testing methodologies, which have enhanced the stability, sensitivity, and durability of HTFSGs under extreme conditions. This article reviews the developmental trajectory of HTFSG research, focusing on the strain mechanisms of sensitive materials and recent advancements in ceramic-metal thin films, ceramic-semiconductor thin films, and metal-based thin films for HTFSGs in terms of structural design, thin-film deposition processes, and material properties. In addition, current challenges and future research directions are discussed to provide valuable insights for future studies.

This paper presents a novel antimony-doped tin dioxide (ATO) thin-film strain gauge (TFSG) designed for strain measurement in ultra-high-temperature environments. Through systematic experimentation, the optimal fabrication conditions were identified as a sputtering atmosphere with an argon-to-oxygen (Ar/O-2) ratio of 40:0, annealing in a nitrogen (N-2) atmosphere, and an annealing temperature of 800 degrees C. Under these conditions, the resistance change rate of the ATO TFSG decreases with increasing temperature. However, between 600 degrees C and 700 degrees C, the resistance change rate temporarily increases before resuming its decline, likely due to phase transitions and oxygen diffusion. Additionally, the ATO TFSG demonstrates exceptional sensitivity and stability, with a gauge factor (GF) of -5.47.

The conformal integration of thin-film heat flux sensors on complex curved substrates is in great demand for various promising applications. However, the incompatibility of conventional multi-step photolithography with pattern transfer to complex surfaces hinders the application of thin-film heat flux sensors. Herein, we fabricated a thin-film heat flux sensor, containing 80 thermocouple pairs in about 1 cm2 on a turbine blade, using multi-step dry film photolithography and a homemade lithography alignment device for in-situ heat flux monitoring. The protective layer effectively mitigated thermal oxidation of the sensitive layer, ensuring its stability at high temperatures (drift rate of about 3.21 degrees C/h at 900 degrees C). Meanwhile, the fabricated thin-film heat flux sensor reached a sensitivity of 116 mu V/(kW/m2) and measured heat flux up to 564.1 kW/m2 at 877 degrees C. The response time and frequency response were 19.85 ms and 2.1 kHz, respectively. Notably, the sensor demonstrated high repeatability and stability in cycling tests. This work serves as a valuable reference for applying thin-film sensors to various curved components, expanding their potential applications in high-temperature environments.

This paper reports a multi-scale micro/nano hierarchical dendritic mesh wick (HDMW). This structure controls the gradient deposition of dendrites through the generation and migration of hydrogen bubbles, thereby achieving and enhancing heterogeneous transport capabilities. The research results show that the capillary comprehensive evaluation parameter Delta P center dot K of HDMW is as high as 2.71 x 10(-7) N. At a working temperature of 80 degrees C, the maximum heat transfer limit of HDMW-Opti reaches 73.51W, which is approximately 70% higher than that of Plate-Opti. Its highly dense and complex multi-level branching structure not only increases the specific surface area but also forms effective fluid channels, thereby enhancing the heterogeneity of capillary forces and liquid flow.

Instantaneous heat flux monitoring of high-temperature components in extreme environments is gaining significant attention for aircraft engines. Recently, advancements in microfabrication techniques have enabled the development of thin-film heat flux sensors (TFHFSs). However, fabricating TFHFS on complex aeroengine components, especially in narrow spaces, remains a significant challenge. In this work, the influence of geometric parameters on the sensor's physical properties is systematically investigated using numerical simulation methods. Then, a high-temperature Pt/PtRh thermopile TFHFS is fabricated on the Ni-based turbine blade. Experimental results indicate that the proposed TFHFS exhibits a high sensitivity of 19.38 mu V/(kW/m(2)) and a response time of approximately 21 ms. Notably, the TFHFS has a nearly constant response in three-cycle tests and exhibits excellent repeatability and stability. Furthermore, the high-temperature combustion wind tunnel test confirms that the TFHFS can operate up to 1000 degrees C and withstand a gas flow velocity of 0.9 Mach, indicating that the fabricated TFHFS is suitable for extremely hostile and complex environment measurement applications. This study provides a viable approach for developing various thin-film sensors on complex surfaces and promotes in situ sensing toward practical applications.

This study presents the design and fabrication of an advanced pyroelectric infrared sensor. The sensor incorporates a lanthanum nickelate (LaNiO3) seed layer, which allows for precise control over the orientation of a (001) Pb(Zr0.1Ti0.9)O-3 (PZT(10)/(90)) film, fabricated using micro-electro-mechanical systems (MEMS) techniques. The PZT films demonstrated a permittivity of 173 and a loss tangent of 0.016 at 1 kHz. The pyroelectric coefficient of the PZT10/90 films was measured to be 25nC.cm(-2). K-1 at room temperature. Notably, the figure of merit for detectivity (Fd) achieved by these PZT thin films reached an impressive value of up to 1.87x10(-5) Pa-1/2. Theoretical predictions suggest that PZT-based pyroelectric detectors could attain a detectivity (D*) on the order of approximately 3.97x10(9) cm. Hz(1/2). W-1. To enhance the infrared radiation absorption capabilities of these detectors, silicon nitride-metal composite thin film materials with high absorptivity in the mid-infrared range (3-5 mu m) were strategically designed and synthesized through magnetron sputtering technology. It is anticipated that integrating infrared-absorbing thin films with pyroelectric detectors will significantly improve their efficacy.

Plasmonic near-perfect absorbers, compnsmg metal films with a periodic array of subwavelength openings, were deposited on the surface of aluminum nitride pyroelectric materials to create wavelength-selective mid-infrared detectors. The developed aluminum nitride(AlN) pyroelectric materials demonstrated a relative dielectric constant of 15 and a pyroelectric coefficient of 20 mu C/(m(2) center dot K) at room temperature. For mid- infrared NDIR (nondispersive infrared) gas sensing detection, a narrowband metamaterial optical antenna has been designed and developed to replace traditional infrared optical filters. Simulations indicated near-perfect absorption at a wavelength of 6.84 mu m, with a quality factor reaching 57, which is expected to bring a new breakthrough to gas detection technology.

Indium tin oxide (ITO) is gaining significant attention in the aerospace field for strain measurement due to its remarkable thermal stability and great piezoresistivity under extreme temperature conditions. However, there are fewer research on performance improvement by doping. In this work, we improve the performance of the Aldoped ITO thin-film strain gauges (AITO TFSGs) by two-step annealing in different annealing atmospheres. After the annealing in Air, O2-Air, and N2-Air, the temperature coefficient of resistance (TCR) of AITO TFSGs were 521.72 ppm/degrees C, 934.10 ppm/degrees C, and 577.64 ppm/degrees C, respectively. Notably, the gauge factor (GF) of AITO TFSGs annealed in N2-Air remained stable at 16.9 even at 1250 degrees C. This is because the insulating crystalline phase formed by Al doping enhances the stability of the AITO film, while the substitution of nitrogen atoms for oxygen atoms or oxygen vacancies further reinforces the structure, resulting in superior performance. Therefore, the doping method and annealing strategy proposed in this work could provide significant guidance for the development of high-temperature strain gauge for ultra-high temperature application.

In this paper, polycrystalline Sc0.2Al0.8N pyroelectric thin films with (002) orientation as the main orientation were prepared on Si-SiO2-Mo substrates using direct current reactive magnetron sputtering with an Sc0.2Al0.8 target, and a pyroelectric detector was designed and fabricated. The test results shows that the pyroelectric coefficient is stable around 15 mu C.m(-2).K-1 at 35-70 degrees C, the dielectric constant was 15.76 at 1 kHz, the dielectric loss was 0.052. Thermoelectric devices based on Sc0.2Al0.8N thin films were prepared using MEMS technology. To further enhance the absorption rate of the mid infrared band, candle soot and candle soot-Au nano absorption layers were developed and prepared. The test results show that the candle soot-Au nano absorption layer has an absorption rate close to 100% in the 3-8 mu m band, and the device with integrated candle soot absorption layer has an absorption rate better than 90% in the 3-8 mu m band. The device's pyroelectric response current is also tested.

In this paper, the PZT10/90 thin film was successfully deposited on the Pt/TiO2/SiO2/Si substrate using RF magnetron sputtering, and the dielectric and pyroelectric properties of the thin film were measured and characterized. The measurements show that the dielectric constant of the PZT10/90 thin film is further reduced compared to the previously reported PZT30/70 thin films, which is beneficial for improving the figure of merit of the PZT. The dielectric constant and loss tangent of the PZT10/90 thin film are 173 and 0.016 at 1kHz and the pyroelectric coefficient of the thin film is 20 nC center dot cm(-2)center dot K-1 at room temperature. In addition, a pyroelectric infrared detector based on the PZT thin film was designed, a feasible detector fabrication process was proposed, and the structure of the pyroelectric infrared detector was optimized using simulation software based on the finite element method. The developed infrared detector has promising applications in the fields of spectroscopic instruments and smart seekers.

Highly integrated pyroelectric detectors have been widely used in infrared spectrometers and gas detection. Aluminum nitride(AlN) has excellent compatibility with CMOS processes and is often used to fabricate piezoelectric and optoelectronic devices with superior performance. This study proposes a pyroelectric detector with AlN thin film as the sensitive element and integrated metamaterial absorber. Magnetron sputtering technology was used to prepare the AlN thin film as the sensitive element. To achieve narrowband specific absorption subsequently, a three-layer metamaterial absorber structure was designed and simulated. Preliminary processing of AlN pyroelectric detectors was performed based on MEMS technology.The designed narrowband absorbing structure exhibits near unity specific absorption, with a quality factor of 17.75. This study preliminarily verifies the application potential of AlN thin films in mid-infrared pyroelectric sensors, and realizes narrowband absorption through metamaterial structures, laying the foundation for the development of mid-infrared gas detection sensors.

Harvesting energy from nature, such as mechanical energy, thermal energy, and biomass energy, has become an effective way to supply power for self-driven sensing and Internet of Things (IoT) applications. Among that, solar-driven thermoelectric (STE) device takes advantage of all-solid-state energy conversion, such as no noise, easy access, and free of wear, exhibiting great potential. Here, we propose a solar-driven thermoelectric device for harvesting solar energy, based on Micro Electromechanical System (MEMS) technology. Specifically, the optimization of solar absorptances of structural layers significantly improved the photo-thermo-electric conversion performance. Furthermore, the electrical output strongly depends on temperature difference dominated by the absorptance difference. Therefore, the reported device can be free of traditional heat sink, which greatly simplifies its structure and expands the working conditions, especially in microdevices. Particularly, a continuous output voltage of 0.34 V/cm2 is achieved with concentrated solar radiation, demonstrating its potential under no heat sink conditions. Besides, a fast response (4.2 ms under 660 nm laser) is achieved benefitting from the micron-size solar absorber, showing its significance in sensing applications. Finally, the proposed STE device is utilized to harvest outdoor solar energy, displaying promising potential in solar energy harvesting devices and providing an insightful perspective for thermoelectric applications.

MEMS-based chip calorimeters are characterized by high integration, miniaturization, high sensitivity, and fast response. However, the sensitivity still faces challenges among biomedical and many other tiny thermal effect detections. This paper presents a miniaturized, highly sensitive microfluidic chip calorimeter with low reactant consumption. It consists of 0.32 mu L microfluidic chambers and polyimide(PI)-based thermal sensor. The thermal sensor comprises a high-performance Bi2Te3-Sb2Te3 thermopile suspending on PI substrate. This greatly eliminates the heat dissipation of the reaction chamber, contributing to a high sensitivity. As a result, the chip calorimeter exhibits a power sensitivity of 8.64 V/W, and a thermal detection resolution of 201 nW. Besides, it performs excellently in detecting exothermic ethanol-diluted and glucose oxidation reactions. Moreover, with the help of enzyme immobilization process, it successfully detected glucose from the aqueous solution. These results indicate the chip calorimeter owns a promising potential in biomedical applications.

Double ceramic layer thermal barrier coatings (DLC-TBCs) are favored for combining the benefits of top and bottom ceramic materials. The thickness ratio of the top and bottom ceramic layers significantly impacts the performance of the DLC-TBCs. In the design process, it is generally desired to balance its thermal insulation properties with a long service life. Therefore, this study establishes a multi-objective parameter optimization design method based on NSGA-II to optimize the thickness of the CeYSZ/Al2O3 DCL-TBCs. Experimental verification of the coating performance was conducted based on the optimization results. Firstly, based on theoretical and numerical models, a quantitative analysis was conducted on the effects of the thickness of each material in the CeYSZ/Al2O3 DCL-TBCs system on thermal insulation and thermal stress. Space parameters were obtained using optimal Latin hypercube sampling, and a radial basis function (RBF) neural network surrogate model was constructed based on the numerical calculation results. Sensitivity analysis was employed to evaluate the impact of the total thickness of the TBCs and the thickness of the Al2O3 ceramic layer on the objective function. Finally, NSGA-II was utilized for optimization. The obtained Pareto optimal solution set was validated, showing that the performance of the CeYSZ 190 μm/Al2O3 120 μm DLC-TBCs satisfied the requirements. Therefore, TBCs of different thicknesses were sprayed and subjected to thermal insulation and thermal shock experiments. The results demonstrated that the optimized TBCs significantly improved service life without compromising thermal insulation, providing a new approach for the subsequent design of DLC-TBCs structures.