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Contactless and label-free detection of urea content in aqueous solutions is of great interest in chemical, biomedical, industrial, and automotive applications. In this work, we demonstrate a compact and low-cost instrumental configuration for label-free, reagent-free, and contactless detection of urea dissolved in water, which exploits the absorption properties of urea in the near-infrared wavelength region. The intensity of the radiation transmitted through the fluid under test, contained in a rectangle hollow glass tubing with an optical pathlength of 1 mm, is detected in two spectral bands. Two low-cost, low-power LEDs with emission spectra centered at λ = 1450 nm and λ = 2350 nm are used as readout sources. The photodetector is positioned on the other side of the tubing, in front of the LEDs. The detection performances of a photodiode and of a thermal optical power detector have been compared, exploiting different approaches for LED driving current modulation and photodetected signal processing. The implemented detection system has been tested on urea–water solutions with urea concentrations from 0 up to 525 mg/mL as well as on two samples of commercial diesel exhaust fluid ("AdBlue™"). Considering the transmitted intensity in presence of the urea–water solution, at λ = 1450 nm and λ = 2350 nm, normalized to the transmitted intensity in presence of water, we demonstrate that their ratio is linearly related to urea concentration on a wide range and with good sensitivity. [ABSTRACT FROM AUTHOR]

This paper presents an innovative approach to the integration of thermoelectric microgenerators (μTEGs) based on thick-film thermopiles of planar constantan–silver (CuNi-Ag) and calcium cobaltite oxide–silver (Ca3Co4O9-Ag) thick-film thermopiles with radio frequency identification (RFID) technology. The goal was to consider using the TEG for an active or semi-passive RFID tag. The proposed implementation would allow the communication distance to be increased or even operated without changing batteries. This article discusses the principles of planar thermoelectric microgenerators (μTEGs), focusing on their ability to convert the temperature difference into electrical energy. The concept of integration with active or semi-passive tags is presented, as well as the results of energy efficiency tests, considering various environmental conditions. On the basis of the measurements, the parameters of thermopiles consisting of more thermocouples were simulated to provide the required voltage and power for cooperation with RFID tags. The conclusions of the research indicate promising prospects for the integration of planar thermoelectric microgenerators with RFID technology, opening the way to more sustainable and efficient monitoring and identification systems. Our work provides the theoretical basis and practical experimental data for the further development and implementation of this innovative technology. [ABSTRACT FROM AUTHOR]

The micro-electromechanical system (MEMS) infrared thermopile is the core working device of modern information detection systems such as spectrometers, gas sensors, and remote temperature sensors. We presented two different structures of MEMS infrared thermopiles based on suspended film structures. They both deposited silicon nitride over the entire surface as a passivated absorber layer in place of a separate absorber zone, and the thermocouple strip was oriented in the same direction as the temperature gradient. The same MEMS preparation process was used and finally two different structures of the thermopile were characterized separately for testing to verify the impact of our design on the detector. The test results show that the circular and double-ended symmetrical thermopile detectors have responsivities of 27.932 V/W and 23.205 V/W, specific detectivities of 12.1×107 cm·Hz1/2·W−1 and 10.1×107 cm·Hz1/2·W−1, and response time of 26.2 ms and 27.06 ms, respectively. In addition, rectangular double-ended symmetric thermopile has a larger field of view than a circular thermopile detector, but is not as mechanically stable as a circular thermopile. [ABSTRACT FROM AUTHOR]

Abstract The micro-electromechanical system (MEMS) infrared thermopile is the core working device of modern information detection systems such as spectrometers, gas sensors, and remote temperature sensors. We presented two different structures of MEMS infrared thermopiles based on suspended film structures. They both deposited silicon nitride over the entire surface as a passivated absorber layer in place of a separate absorber zone, and the thermocouple strip was oriented in the same direction as the temperature gradient. The same MEMS preparation process was used and finally two different structures of the thermopile were characterized separately for testing to verify the impact of our design on the detector. The test results show that the circular and double-ended symmetrical thermopile detectors have responsivities of 27.932 V/W and 23.205 V/W, specific detectivities of 12.1×107 cm·Hz1/2·W−1 and 10.1×107 cm·Hz1/2·W−1, and response time of 26.2 ms and 27.06 ms, respectively. In addition, rectangular double-ended symmetric thermopile has a larger field of view than a circular thermopile detector, but is not as mechanically stable as a circular thermopile.

This paper presents an innovative approach to the integration of thermoelectric microgenerators (μTEGs) based on thick-film thermopiles of planar constantan–silver (CuNi-Ag) and calcium cobaltite oxide–silver (Ca3Co4O9-Ag) thick-film thermopiles with radio frequency identification (RFID) technology. The goal was to consider using the TEG for an active or semi-passive RFID tag. The proposed implementation would allow the communication distance to be increased or even operated without changing batteries. This article discusses the principles of planar thermoelectric microgenerators (μTEGs), focusing on their ability to convert the temperature difference into electrical energy. The concept of integration with active or semi-passive tags is presented, as well as the results of energy efficiency tests, considering various environmental conditions. On the basis of the measurements, the parameters of thermopiles consisting of more thermocouples were simulated to provide the required voltage and power for cooperation with RFID tags. The conclusions of the research indicate promising prospects for the integration of planar thermoelectric microgenerators with RFID technology, opening the way to more sustainable and efficient monitoring and identification systems. Our work provides the theoretical basis and practical experimental data for the further development and implementation of this innovative technology.

Aiming at the shortcomings of the traditional engineering experience in designing thin-film heat flow meters, such as low precision and long iteration time, the finite element analysis model of thin-film heat flow meters is established based on finite element simulation methods, and a double-type thin-film heat flow sensor based on a copper/concentrate thermopile is made. The influence of the position of the thermal resistance layer, heat flux density and thickness of the thermal resistance layer on the temperature gradient of the hot and cold ends of the heat flow sensor were comprehensively analyzed by using a simulation method. When the applied heat flux density is 50 kW/m2 and the thermal resistance layer is located above and below the thermopile, respectively, the temperature difference between the hot junction and the cold junction is basically the same, but comparing the two, the thermal resistance layer located above is more suitable for rapid measurements of heat flux at high temperatures. In addition, the temperature difference between the hot and cold contacts of the thin-film heat flux sensor increases linearly with the thickness of the thermal resistance layer. Finally, we experimentally tested the response–recovery characteristics of the sensors, with a noise of 2.1 μV and a maximum voltage output of 15 μV in a room temperature environment, respectively, with a response time of about 2 s and a recovery time of about 3 s. Therefore, the device we designed has the characteristic of double-sided use, which can greatly expand the scope of use and service life of the device and promote the development of a new type of heat flow meter, which will provide a new method for the measurement of heat flow density in the complex environment on the surface of the aero-engine. [ABSTRACT FROM AUTHOR]

In this research, improvisation was carried out by modifying the market IR thermopile which functions as a thermal conductivity detector to measure the concentration of CO2 gas in the gas mixture. Four thermopiles are configured with a Wheatstone bridge with the aim of increasing the accuracy of the measurement system in detecting changes in CO2 concentration in the gas mixture (N2 and CO2). Using the bridge configuration of these four thermopiles, this measurement system can measure changes in CO2 concentration in small orders. The sensor developed is easy to manufacture, low cost, and has high linearity as evidenced by a correlation coefficient of 0.9943. From the experiments carried out, the sensor works quite accurately in detecting CO2 concentrations with the sensor’s sensitivity of -88.19 Volt/%, the detection range is 0% to 100%, and the RMS error value is 2.25.

Grégory Ben-Sadoun,1,2 Emeline Michel,3,4 Cédric Annweiler,1,5– 7 Guillaume Sacco3,5,8 1Department of Geriatric Medicine and Memory Clinic, Research Center on Autonomy and Longevity, University Hospital of Angers, Angers, France; 2Normandie Université, UNICAEN, INSERM, COMETE, CYCERON, CHU Caen, Caen, 14000, France; 3Université Côte d’Azur, Centre Hospitalier Universitaire de Nice, Clinique Gériatrique du Cerveau et du Mouvement, Nice, France; 4Université Côte d’Azur, LAMHESS, Nice, France; 5Laboratoire de Psychologie des Pays de la Loire, Univ Angers, Université de Nantes, EA 4638 LPPL, SFR CONFLUENCES, Angers, F-49000, France; 6School of Medicine, Health Faculty, University of Angers, Angers, France; 7Robarts Research Institute, Department of Medical Biophysics, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada; 8Université Côte d’Azur, CoBTek, Nice, FranceCorrespondence: Grégory Ben-SadounDepartment of Geriatric Medicine and Memory Clinic, Research Center on Autonomy and Longevity, University Hospital of Angers, Angers, FranceEmail bensadoun.gregory@hotmail.fr; gregory.bensadoun@chu-angers.fr; gregory.ben-sadoun@unicaen.frAbstract: Systems using passive infrared sensors with a low resolution were recently proposed to answer the dilemma effectiveness–ethical considerations for human fall detection by Information and Communication Technologies (ICTs) in older adults. How effective is this type of system? We performed a systematic review to identify studies that investigated the metrological qualities of passive infrared sensors with a maximum resolution of 16× 16 pixels to identify falls. The search was conducted on PubMed, ScienceDirect, SpringerLink, IEEE Xplore Digital Library, and MDPI until November 26– 28, 2020. We focused on studies testing only these types of sensor. Thirteen articles were “conference papers”, five were “original articles” and one was a found in arXiv.org (an open access repository of scientific research). Since four authors “duplicated” their study in two different journals, our review finally analyzed 15 studies. The studies were very heterogeneous with regard to experimental procedures and detection methods, which made it difficult to draw formal conclusions. All studies tested their systems in controlled conditions, mostly in empty rooms. Except for two studies, the overall performance reported for the detection of falls exceeded 85– 90% of accuracy, precision, sensitivity or specificity. Systems using two or more sensors and particular detection methods (eg, 3D CNN, CNN with 10-fold cross-validation, LSTM with CNN, LSTM and Voting algorithms) seemed to give the highest levels of performance (> 90%). Future studies should test more this type of system in real-life conditions.Keywords: fall detection, older adults, passive infrared sensor, thermal sensor, thermopile

In this letter, we report a performance enhancement approach for MEMS thermopile Pirani sensors through in-situ integration of nanoforests. The nanoforests not only increase the light absorption of the thermopile, resulting in an improved output voltage, but also increase the contact area and heat exchange sites for gas molecules due to their high porosity and large surface area to volume ratio, subsequently improve the gas heat conduction, extend pressure detection range and increase sensitivity of the Pirani sensor. With integration of the nanoforests, the lower detection limit of the sensor is widened by one order of magnitude compared with the pristine sensor, and the maximum increment in sensitivity reached 56.7%. Moreover, such a sensor can be easily fabricated with a CMOS-compatible process, thus is suitable for mass production. This work provides a new route to enhance performance of current MEMS thermopile Pirani sensors. [ABSTRACT FROM AUTHOR]

Elevated body temperature (fever) can be a common symptom of a medical condition, such as a viral or bacterial infection, including SARS-CoV-2 or influenza. Non-contact infrared thermometers are able to measure forehead temperature in a timely manner and were used to perform a fast fever screening in a population. However, forehead temperature measurements differ greatly from basal body temperatures, and are the target of massive perturbations from the environment. Here we gathered a dataset of N=18024 measurements using the same precision infrared sensor in different locations while tracking both outside temperature, room temperature, time of measurement, and identity. Herein, we propose a method able to extract and remove the influence of external perturbations, and set the threshold for fever detection to 37.38 °C, after calibration and temperature correction. This method can help manufacturers and decision-makers to build and use more accurate tools so as to maximize both sensitivity and specificity of the screening protocol. [ABSTRACT FROM AUTHOR]

In this research, a new electro-optical-thermal modeling is proposed and built by simulation program with integrated circuit emphasis (SPICE). In particular, it is constructed for use in the non-dispersive infrared (NDIR) sensing technique of gas concentration. This model, based on the theory of circuitry and the Beer-Lambert law, includes various equivalent elements for the optics, sensor, and circuits. To build and investigate the validity of the proposed model, an NDIR for measurement of CO2 is built with the hybrid combination of a thermopile sensor with a specific wavelength filter, an infrared micro electro mechanical systems (MEMS) heater, an optical tube, amplification circuits with a chopper amplifier, advanced RISC machine (ARM)-based micro processing unit and discrete electronic devices. The thermal properties of the light source with periodic modulation have been studied from the output signal of a thermopile within the limit of modulation frequency. Based on the thorough measurements of output signals and transient responses, the thermal and optical parameters of the sensor and optical components for this model are extracted. The comparison of the simulation and experimental data of the NDIR measurement for different CO2 concentrations shows a great agreement with a maximum error of 0.27% at 3500 ppm. This approach allows for the development of a high-level sensor and circuit integrated simulation based on the most fundamental principles and multiple variables. [ABSTRACT FROM AUTHOR]

Aiming at the shortcomings of the traditional engineering experience in designing thin-film heat flow meters, such as low precision and long iteration time, the finite element analysis model of thin-film heat flow meters is established based on finite element simulation methods, and a double-type thin-film heat flow sensor based on a copper/concentrate thermopile is made. The influence of the position of the thermal resistance layer, heat flux density and thickness of the thermal resistance layer on the temperature gradient of the hot and cold ends of the heat flow sensor were comprehensively analyzed by using a simulation method. When the applied heat flux density is 50 kW/m2 and the thermal resistance layer is located above and below the thermopile, respectively, the temperature difference between the hot junction and the cold junction is basically the same, but comparing the two, the thermal resistance layer located above is more suitable for rapid measurements of heat flux at high temperatures. In addition, the temperature difference between the hot and cold contacts of the thin-film heat flux sensor increases linearly with the thickness of the thermal resistance layer. Finally, we experimentally tested the response–recovery characteristics of the sensors, with a noise of 2.1 μV and a maximum voltage output of 15 μV in a room temperature environment, respectively, with a response time of about 2 s and a recovery time of about 3 s. Therefore, the device we designed has the characteristic of double-sided use, which can greatly expand the scope of use and service life of the device and promote the development of a new type of heat flow meter, which will provide a new method for the measurement of heat flow density in the complex environment on the surface of the aero-engine.

In the materials of the article, the following issues are considered in relation to this problem: the efficiency of temperature reduction in a thermoelectric cooler; the nature of the destruction of an electric charge by thermal impulses; operating modes of thermopiles in brake friction pairs. The purpose of the article is to reduce the value of the ratio between the Peltier ("useful") and Joule ("harmful") effects in electric and thermal currents circulating in the thermopile branches, and the use of thermoelectric cooling in the friction pairs of the tape-shoe brake of the drawworks. The thermopiles installed in the friction linings of the brake band on its incoming and outgoing branches operated in the modes of a thermoelectric cooler and a thermoelectric generator, respectively. It has been established that when the energy loading is quasi- leveling in terms of the belt sweep angle of the pulley, the following is achieved on average: a decrease in energy loading to 20 %, an increase in the dynamic coefficient of friction by 11 %, and a decrease in liner wear by 8.5 % when they operate in the range of surface-bulk temperatures below the acceptable value for their materials. [ABSTRACT FROM AUTHOR]

This paper presents a detailed analysis of a micromachined thermopile detector featuring high responsivity and a versatile mosaic structure, based on 128 60 µm × 60 µm pixels connected in series and/or in parallel. The mosaic structure is based on the one employed for the thermal sensor known as TMOS, which consists of a CMOS-SOI transistor embedded in a suspended and thermally isolated absorbing membrane, released through microelectro mechanical system (MEMS) post-processing. Two versions of the thermopile detector, featuring different series/parallel connections, are presented and were experimentally characterized. The most performant of the two achieved 2.7 × 10 4 V/W responsivity. The thermopile sensors' performances are compared to that of the TMOS sensor, adopting different configurations, and their application as proximity detectors was verified through measurements. [ABSTRACT FROM AUTHOR]

Combined use of thermal analysis techniques can realize complementarity of different characterization methods. Comprehensive thermal analysis with both thermogravimetric analysis and differential thermal analysis (TG/DTA) can measure not only mass change of a sample but also its temperature change during programmed heating-induced reaction or phase transition processes, thereby obtaining multiaspect thermal information of the material such as dehydration, structural decomposition, phase change and thermal stability. This study proposes and develops a MEMS chip-based TG/DTA microsystem that integrates both programmed heating and detecting elements into a TG chip and a DTA chip to enable the microinstrument performing TG/DTA joint characterization under microscope observation. The TG chip contains a self-heating resonant microcantilever to measure heating-induced mass change of a sample and the DTA chip is with a microheater and a temperature-detecting thermopile integrated on a suspended thermal-insulating diaphragm. Only nanogram and microgram-level samples are needed for the TG and DTA chips, thereby achieving safe measurement to energetic materials such as strong oxidants. The chip-based microinstrument surpasses the state-of-the-art commercial TG/DTA instruments that have, in the long term, suffered from large sample-amount (milligram level) requirements and have been unable to measure energetic materials. Compared with commercial instruments, the chip-based microinstrument is advantageous given its more accurate analysis, much higher heating rate, much smaller instrument volume and much lower power consumption, etc. The microinstrument has been fabricated by using wafer-level MEMS techniques. Testing results show that the mass-detection sensitivity of the TG-chip is as high as 0.45 Hz/pg in air and the temperature sensitivity of the DTA chip achieves 2.9 mV/K under the high heating rate of 25 °C/s. The strong oxidant of KMnO4 is analyzed with the TG/DTA joint characterization under microscopic observation. At the same time as microscope observation of the thermal decomposition phenomena, two-step thermal decomposition process of KMnO4 is identified and the thermal decomposition temperatures are obtained. The TG/DTA microinstrument is promising to be applied for study of various materials. [ABSTRACT FROM AUTHOR]

We propose a numerical model for efficient design and optimization of a novel infrared (IR) detector array, fabricated on a single micro-electro-mechanical system (MEMS) membrane based on silicon on insulator (SOI) technology. The model is based on a finite element method (FEM) and is used to investigate the effect of heat transfer, at pixel scale, on the thermopile array’s responsivity and crosstalk performance. We show that optimal operational conditions can be achieved by modifying a combination of design elements, including the pixel size, the interpixel metal heatsinking tracks, as well as the insertion of air gaps between pixels. We find that the combined effect of copper heatsinking tracks and that of air gaps can reduce pixel crosstalk by 65% while increasing the responsivity by 6.4%. The model improves our understanding of the thermal effects in these devices, and can serve as a design tool for a growing number of low-cost industrial and consumer applications. [ABSTRACT FROM AUTHOR]

Diffusion processes on the contact areas of the metal-solder-semiconductor system are experimentally studied in this work. Diffusion coefficients, activation energies and pre-exponential factors in samples commutated with solders based on Pb-Sb are determined. It has been established that lead-based solder has a significantly higher inertness to thermoelectric materials. Humans are currently facing complex challenges such as rising energy costs, pollution and global warming. To reduce their consequences, scientists are concentrating on improving power generators focused on energy harvesting. Thermoelectric generators (TEGs) have demonstrated their ability to convert thermal energy directly into electricity through the Seebeck effect. Due to the unique advantages, they present, thermoelectric systems have emerged over the past decade as a promising alternative among other technologies for the production of clean energy. [1-11]. Switching is the most time-consuming and responsible operation in the manufacture of thermoelectric modules. In them, which include a significant number of junctions, failures most often occur due to broken contacts [2-8]. To prevent the harmful effects of internal mechanical stresses, in the manufacture of thermoelectric batteries, it is necessary to use a damping layer between the branch and the connecting plate [3-14]. The damping layer is made of a material with sufficient plasticity and low ohmic resistance. It is usually made from lead. The results of the research showed the advantages of using a single -wire technology for soldering with Pb - Sb eutectic solder using an anti -diffusion layer of chemically deposited nickel. In this case, the eutectic solder Pb - Sb in the contact simultaneously performs the role of a damper and a switching solder.

A micromachined thermopile infrared sensor is designed and optimized with high detective sensitivity in the article. A matched chopper operational amplifier with good linearity is implemented for signal processing. Optimizations of the sensor’s structure are proposed by the adjustment of the length of the thermocouple pairs and the filling of the back-etched cavity based on the adopted thermocouple materials. A passivation layer is implemented to minimize the flicker noise of the sensor. Based on the requirement of the optimized thermopile sensor system, both the flicker noise and the low-frequency noise of the system are suppressed for achieving high sensitivity. The chopper operational amplifier circuit with a single-ended closed-loop diagram is specifically designed for signal amplification and noise suppression. The fabricated device shows improved characterizations, with the responsivity of 182.72 V/W, detectivity of $2.47\times 10^{{8}}$ cmHz1/2/W, time constant of 10 ms, and total resistance of 270 $\text{k}\Omega $. The sensitivity of the designed system, including the sensor and the amplifier, is about 15 mV/°C, when the gain is 40 dB and the sensor-target distance is 3 cm. The system shows wide applications in the fields of noncontact temperature measurement and other special applications. [ABSTRACT FROM AUTHOR]

In this research, a new electro-optical-thermal modeling is proposed and built by simulation program with integrated circuit emphasis (SPICE). In particular, it is constructed for use in the non-dispersive infrared (NDIR) sensing technique of gas concentration. This model, based on the theory of circuitry and the Beer-Lambert law, includes various equivalent elements for the optics, sensor, and circuits. To build and investigate the validity of the proposed model, an NDIR for measurement of CO2 is built with the hybrid combination of a thermopile sensor with a specific wavelength filter, an infrared micro electro mechanical systems (MEMS) heater, an optical tube, amplification circuits with a chopper amplifier, advanced RISC machine (ARM)-based micro processing unit and discrete electronic devices. The thermal properties of the light source with periodic modulation have been studied from the output signal of a thermopile within the limit of modulation frequency. Based on the thorough measurements of output signals and transient responses, the thermal and optical parameters of the sensor and optical components for this model are extracted. The comparison of the simulation and experimental data of the NDIR measurement for different CO2 concentrations shows a great agreement with a maximum error of 0.27% at 3500 ppm. This approach allows for the development of a high-level sensor and circuit integrated simulation based on the most fundamental principles and multiple variables.

Heat flux sensors (HFSs) have potential in enabling applications that require direct and instantaneous tracking of thermal energy transfer. To facilitate the widespread use of the sensors, the sensors have to be robust and feasible to implement, while maintaining high sensitivity, fast response time, and low thermal obtrusiveness. However, most of the currently available HFSs are either challenging to manufacture or ill-suited for surface heat flux measurement because of their mechanical or thermal characteristics. In this article, the design of a novel microelectromechanical systems (MEMS) HFS structure intended for surface heat flux measurements is presented. A prototype batch is manufactured and the electrical performance of the prototype sensors is compared with commercially available HFSs. Results show that sensors with similar sensitivity as commercial sensors can be made by using MEMS methods. [ABSTRACT FROM AUTHOR]

This paper presents a detailed analysis of a micromachined thermopile detector featuring high responsivity and a versatile mosaic structure, based on 128 60 µm × 60 µm pixels connected in series and/or in parallel. The mosaic structure is based on the one employed for the thermal sensor known as TMOS, which consists of a CMOS-SOI transistor embedded in a suspended and thermally isolated absorbing membrane, released through microelectro mechanical system (MEMS) post-processing. Two versions of the thermopile detector, featuring different series/parallel connections, are presented and were experimentally characterized. The most performant of the two achieved 2.7 × 104 V/W responsivity. The thermopile sensors’ performances are compared to that of the TMOS sensor, adopting different configurations, and their application as proximity detectors was verified through measurements.

Temperature measurement in microwave systems is essential for thermally driven processes, namely, catalytic reactions and ceramic sintering. Although, the application of direct thermometry methods, namely, thermocouples, have been commonly articulated in the available literature, however, contacted temperature measurement mechanisms have aroused concerns associated with the disruption of the electromagnetic field and local distortion of the field pattern leading to unprecedented measurement uncertainties. Consequently, the application of optical measurement methods has been advocated to diminish the associated concerns. However, due to the economical constrains and measurement range restrictions, the application of optical measurement systems, namely, pyrometers and optical fibers, has been deferred. In this study, an infrared thermopile, a precise and feasible temperature measurement system has been developed and calibrated to perform in microwave irradiation. Furthermore, the accuracy of the developed temperature system has been compared with the thermometry technique. It was concluded that thermopile stipulates unrivalled precision, succeeding a profound calibration procedure. It was further demonstrated that the thermopile is capable of the temperature measurement of the dielectric surfaces, exclusively, while the grounded thermocouple monitored the bulk temperature, a proportion of the gas phase and the solid phase temperature values. Consequently, the application of a thermopile coupled with a thermometry measurement method has been proposed to monitor the temperature of the dielectric catalyst active sites in gas-solid catalytic microwave-heated reactions.

Combined use of thermal analysis techniques can realize complementarity of different characterization methods. Comprehensive thermal analysis with both thermogravimetric analysis and differential thermal analysis (TG/DTA) can measure not only mass change of a sample but also its temperature change during programmed heating-induced reaction or phase transition processes, thereby obtaining multiaspect thermal information of the material such as dehydration, structural decomposition, phase change and thermal stability. This study proposes and develops a MEMS chip-based TG/DTA microsystem that integrates both programmed heating and detecting elements into a TG chip and a DTA chip to enable the microinstrument performing TG/DTA joint characterization under microscope observation. The TG chip contains a self-heating resonant microcantilever to measure heating-induced mass change of a sample and the DTA chip is with a microheater and a temperature-detecting thermopile integrated on a suspended thermal-insulating diaphragm. Only nanogram and microgram-level samples are needed for the TG and DTA chips, thereby achieving safe measurement to energetic materials such as strong oxidants. The chip-based microinstrument surpasses the state-of-the-art commercial TG/DTA instruments that have, in the long term, suffered from large sample-amount (milligram level) requirements and have been unable to measure energetic materials. Compared with commercial instruments, the chip-based microinstrument is advantageous given its more accurate analysis, much higher heating rate, much smaller instrument volume and much lower power consumption, etc. The microinstrument has been fabricated by using wafer-level MEMS techniques. Testing results show that the mass-detection sensitivity of the TG-chip is as high as 0.45 Hz/pg in air and the temperature sensitivity of the DTA chip achieves 2.9 mV/K under the high heating rate of 25 °C/s. The strong oxidant of KMnO4 is analyzed with the TG/DTA joint characterization under microscopic observation. At the same time as microscope observation of the thermal decomposition phenomena, two-step thermal decomposition process of KMnO4 is identified and the thermal decomposition temperatures are obtained. The TG/DTA microinstrument is promising to be applied for study of various materials.

In this letter, we pattern thermocouples on the surface of pyramidally-textured dielectric film by careful control of etching and lithography process successfully. Taking advantage of the low thermal conductance and high infrared absorption of the textured dielectric film, the temperature difference between the hot and cold junctions can be increased when this dielectric-film absorber is heated by IR radiation. The fabricated thermopile with 184 pairs of P+poly-Si/Au thermocouples has responsivity, detectivity, and response time constant of $147.21\pm 4.39\,\,\text{V}\cdot \text{W}\,\,^{{-{1}}},{1.71} \pm {0.04} \times {10}^{{8}}$ cm $\cdot $ Hz $^{\text {1/2}}\cdot \text{W}^{-{1}}$ , and 9.44± 0.25 ms in air, respectively. Compared to the controlled thermopile based on flat dielectric film, the responsivity and detectivity are significantly improved by more than 58%, while the time constant is still kept less than 10 ms. These results indicate the feasibility of patterning thermocouples on the surface of pyramidally-textured dielectric film for achieving high-performance thermopiles. [ABSTRACT FROM AUTHOR]

Calorimeter is a powerful instrument that enables high-throughput detection of biochemical reaction heat without any label and immobilization of reactants. This paper introduces a novel, highly-sensitive, little reactant consumption, miniaturized microfluidic chip calorimeter integrated with three identical PDMS microfluidic chambers of $1.28~\mu $ L and a polyimide-based flexible heat sensor. The flexible heat sensor contains a Bi-Sb thermopile and three identical micro heaters. The device demonstrates a novel response time of 0.716s,the heat detection sensitivity was about 5.3V/W and the heating power detecting resolution was about 51nW in static state. The device showed excellent performance in heat detection of ethanol dilution and microbial metabolism (BS168 and HT66 bacteria suspension) exotherm. The micro fluidic chip calorimeter has great potential to be applied in biochemical process monitoring applications. [ABSTRACT FROM AUTHOR]

The infrared absorption efficiency (IAE) enhancement of the complementary-metal-oxide-semiconductorCMOS compatible thermopile with special subwavelength hole arrays in an active area was numerically investigated by the finite-difference time-domain method. It was found that the absorption efficiency of that thermopile was enhanced when the subwavelength rectangular-hole array added extra rectangular-columnar or ellipse-columnar structures in the hole array. The simulation results show that the IAEs of the better cases for the three types of rectangular columns and three ellipse columns were increased by 14.4% and 15.2%, respectively. Such special subwavelength hole arrays can be improved by the IAE of the CMOS compatible thermopile. [ABSTRACT FROM AUTHOR]

In this letter, we report a performance enhanced thermopile with rough dielectric film black. The pyramidally-textured structure is in-situ formed in the thin dielectric film as an infrared absorber by hard-molding method. Compared to flat dielectric film-based thermopile with the same size, the output voltage, responsivity, and detectivity of the thermopile with rough dielectric film black can be improved by approximately 38%, while the response time constant remains less than 10 ms. The pyramidally- textured dielectric film provides a new opportunity to enhance the performance of thermopiles with the simple process as well as low cost. [ABSTRACT FROM AUTHOR]

Besides the application of the photonic crystal for the photodetector in the visible range, the infrared devices proposed with subwavelength structure are numerically and experimentally investigated thoroughly for infrared radiation sensing in this research. Several complementary metal oxide semiconductor (CMOS) compatible thermopiles with subwavelength structure (SWS) are proposed and simulated by the FDTD method. The proposed thermopiles are fabricated by the 0.35 μm 2P4M CMOS-MEMS process in TSMC (Taiwan Semiconductor Manufacturing Company). The measurement and simulation results show that the response of these devices with SWS is higher than for those without SWS. The trend of the measurement results is consistent with that of the simulation results. Obviously, the absorption efficiency of the CMOS compatible thermopile can be enhanced when the subwavelength structure exists. [ABSTRACT FROM AUTHOR]

• Monitoring of CO 2 hydrate formation kinetics in reactor by heat balance. • Heat flux measurement by thermopile on the reactor shell. • Highlighting the impact of stirring mobile and speed on hydrates formation kinetics. • Experimental validation by comparison with a mass balance. CO 2 hydrate slurries are promising phase change materials for secondary refrigeration applications. However, the difficulty of experimentally evaluating the crystallization kinetic of slurries limits their industrial use. Hydrate crystallization kinetics monitoring performs traditionally by a reactor mass balance. However, this method requires assumptions on CO 2 liquid phase concentration and the hydration number. This work outlines the development of a specific method to determine kinetics thanks to the direct measure of heat flow through the reactor jacket and its evaluation compared with the mass balance method. The results of each method are then obtained by testing the two kinetic parameters of stirring speed and propeller type. The final hydrate mass fractions obtained with both methods are in good agreement, but the kinetic obtained by the mass balance method is faster than by the heat balance method. [ABSTRACT FROM AUTHOR]

Solid volume fraction is a defining characteristic of multiphase gas–solid flows. In the case of gravity-driven particle curtains, it changes significantly along the flow direction. This has implications for the performance of falling-particle solar receivers, which use particle curtains to capture and store heat from concentrated sunlight. This study reports on the characterization of solid volume fraction as a function of height in gravity-driven particle curtains using optical techniques and simulations performed with a discrete element method (DEM) model. The experimental domain is a hopper-fed vertical channel, and the modeling domain is designed to match the experimental setup. Solid volume fraction was obtained from experimentally measured transmittance using two techniques: (1) a thermopile detector paired with a visible light source and (2) a high-speed camera. The DEM simulations were calibrated by identifying the coefficient of static friction between particles that resulted in equivalent mass flow rates to the experiments. All techniques, including an analytical model derived from first principles and empirical relationships, showed very similar trends of solid volume fraction decreasing along the flow direction, where it drops off rapidly initially before leveling off in a power law relationship. Both experimental and computational tests were performed with 1 mm and 2 mm particles, and solid volume fraction is found to decrease with increasing particle size at any location in the channel. Furthermore, the solid volume fractions calculated from transmittance measurements were found to be sensitive to the optical properties of the particles through Monte Carlo ray tracing simulations. To account for this effect, a new scale factor dependent on particle reflectivity is derived, which leads to significantly improved agreement between experimental and simulated results. A simple, closed-form equation is proposed to transform measured transmittance to a solid volume fraction while accounting for particle reflectivities. Even though solid volume fractions above 0.1 were not measured in this study, the technique developed is suitable to measure even larger solid volume fractions, especially for more reflective particles. [Display omitted] • Thermopile and high-speed camera measurements for gravity-driven particle flows. • Experiments compared with particle tracking and ray tracing simulations. • Modified Beer's law involving particle optical properties and dependent scattering. • New governing equation for transmittance-dependence on optical properties. • Sensitivity of flow behavior to friction and particle size distribution. [ABSTRACT FROM AUTHOR]

Early detecting of fusarium spore in the air is highly desired, as it helps to protect crops from the potential of dangerous fungal disease. This paper focuses on developing a method and building a portable, reliable, and affordable device, which can promptly and continuously detect the presence of fusarium spores in the air. Based on the Beer–Lambert law and the distinct infrared absorbance spectrum of substances, a specification logarithm ratio formula for two different wavelengths is developed. This is the main principle of the detection technique and design of the device. In the system, there are two sensitive infrared thermopiles that work on two specific infrared wavelengths, including $\lambda _{\mathbf {1}} = 6.09 \pm 0.06\,\,\mu \text{m}$ and $\lambda _{\mathbf {2}} = 9.49\pm 0.44\,\,\mu \text{m}$. The thermopiles are used to measure the infrared light intensity emitted by an infrared light source (2–22 $\mu \text{m}$) for the fusarium spore detection analysis. The detection is based on the group distinction coefficient. The Beer–Lambert law also assists in the approximate estimation of the quantity of the spores. For testing the detection ability of the system and the method, besides fusarium spore, other substances, such as sunflower pollen, polyphenol, and starch, were also used in the experiments. The experimental results indicate that the fusarium group-distinction coefficient (1.14 ± 0.15) is distinct from the other investigated substances (pollen: 0.13 ± 0.11, turmeric: 0.79 ± 0.07, and starch 0.94 ± 0.07). The results prove that the system and the proposed method can be used to detect and quantify not only for fusarium but also for other spores, molds, and specific pathogens. [ABSTRACT FROM AUTHOR]

Low-resolution thermal cameras have already been used in the detection of respiratory flow. However, microbolometer technology has a high production cost compared to thermopile arrays. In this work, the feasibility of using a thermopile array to detect respiratory flow has been investigated in multiple settings. To prove the concept, we tested the detector on six healthy subjects. Our method automatically selects the region-of-interest by discriminating between sensor elements that output noise and flow-induced signals. The thermopile array yielded an average root mean squared error of 1.59 b r e a t h s p e r m i n u t e . Parameters such as distance, breathing rate, orientation, and oral or nasal breathing resulted in being fundamental in the detection of respiratory flow. The paper provides the proof-of-concept that low-cost thermopile-arrays can be used to monitor respiratory flow in a lab setting and without the need for facial landmark detection. Further development could provide a more attractive alternative for the earlier bolometer-based proposals. [ABSTRACT FROM AUTHOR]

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Abstract Orbit estimation (OE) is a required significant task in almost all space missions. Accordingly, a wide variety of sensors and estimation algorithms have been developed within the last few decades to this aim. However, the current study proposes a novel autonomous OE method that is purely based on temperature data of six orthogonal surfaces of a three-axis stabilized satellite as it orbits around the Earth. While the utility of satellite surface temperature data has been recently investigated for satellite attitude estimation (AE) assuming its navigational information, the present paper is focused on OE via only temperature data that has not been attended to in the related literature. To this end, it is assumed that satellite surfaces are equipped with small plates that are thermally isolated from the internal heat sources so that their temperature changes mainly arise from environmental radiation emanated mainly from the Sun and the Earth. In this sense, a thermal model is developed and demonstrated to show how the satellite surface temperatures and their time rates are the only ingredients needed, as measurement quantities, for the proposed OE method to produce the satellite navigational data in terms of its position and velocity vectors. In addition, the effect of sensor configuration on state observability and estimation accuracy is investigated while the unscented Kalman filter (UKF) is exploited in the estimation process. Performance and viability of the proposed temperature-based OE are verified through Monte Carlo simulations and a comprehensive sensitivity analysis over orbital parameters, satellite initial conditions, sensor accuracy and attitude error. [ABSTRACT FROM AUTHOR]

Highlights • A measurement system for the internal and external preforms temperature profiles has been developed. • Cheap IR detectors can effectively be used for the purpose. • Measurement uncertainties lower than 2 °C can be achieved if the material emissivity is known. • Using average PET emissivity leads to uncertainties up to 6 °C. • The system allows implementing an in line closed loop temperature control system. Abstract This paper describes a system for the measurement of the internal and external temperature profiles of PET preforms used in the Injection Stretch Blow Moulding (ISBM) process. Many works in literature highlighted the importance of these quantities to improve the production quality of PET bottles, but none addressed the development of a measuring system suitable for this scope. A measuring system based on two thermopiles for the identification of the internal temperature profile and a thermal camera for the measurement of the external one has been designed. The adopted sensors were individually calibrated and the uncertainty budget, accounting for both instrumental uncertainties and the effect of multiple reflections, was derived. A prototype of the measuring system was tested on an industrial ISBM machine. The dependence of the preforms temperature profile on the settings of the ISBM machine was investigated. Results evidenced that the minimum variations of the machine settings induced temperature differences significantly larger than the measurement uncertainty, thus proving the effectiveness of the proposed system. [ABSTRACT FROM AUTHOR]

Highlights • Measurement of concentration of CO 2 gas based on thermal conductivity gas can be done using the thermopile. • The thermopile used for measuring the CO 2 concentration is a modified thermopile without an IR window. • Measurement of gas concentration using thermopile in accordance with the prediction model of Mason and Saxena. Abstract A simple and effective thermal conductivity based CO 2 gas sensor has been successfully developed. The CO 2 sensor consists of a modified IR thermopile sensor without an IR window. The thermopile is heated by the AC current that is applied through the output terminals of the device, which in turn leads to a temperature gradient generating a DC output voltage. The gas exposed to the thermopile simultaneously cool down the thermopile. Thus, the thermopile can simultaneously serve as a heater and temperature sensor. The built-in sensors possess low production costs, low power consumption and are easily manufactured. From the conducted experiments, the sensor can work well, and the results can be validated with the established theory, as evidenced by the RMS error of 0.787. The measurement results are also in a good agreement with the model predictions Mason and Saxena for the thermal conductivity of gas mixtures. [ABSTRACT FROM AUTHOR]

Abstract We report a lab-on-a-chip immunosesnor for quantification of the inflammatory cytokine TNF-α with picomolar sensitivity. The feasibility of the technology was demonstrated via accurate measurement of the concentration of TNF-α in astrocytes cell culture media. The immunoassay was performed in a microfluidic device with an integrated antimony/bismuth thermopile sensor and had a limit of detection of 14 pg mL−1. The device was fabricated using rapid prototyping xurography technique and consisted of two inlets and single outlet. Anti-TNF-α monoclonal antibody was used to capture the analyte while the detection was performed using glucose oxidase-conjugated secondary antibody. Glucose (55 mM) was injected through a sample loop into the fluid flowing within the microfluidic device. A nanovolt meter connected to the thermoelectric sensor recorded the voltage change caused by the enzymatic reaction. Computer simulations using COMSOL Multiphysics were performed to analyze the effect of fluid velocity on the concentration of glucose within the reaction zone. A standard calibration curve was created using serial dilutions of synthetic TNF-α (0–2000 pg mL−1) by plotting the area under the curve of the signal versus the concentration of the analyte. The efficacy of the device was evaluated by quantifying TNF-α in the cell culture medium of lipopolysaccharide stimulated and non-stimulated astrocytes. The results demonstrated high accuracy of the calorimetric immunoassay when compared with gold standard commercial ELISA microplate reader. The immunosensor offers excellent reproducibility, accuracy, and versatility in the choice of the detection enzyme. Highlights • TNF- α was quantified in a microfluidic device with an integrated thermopile with a Seebeck coefficient of 7.14 μV mK−1. • The heat resealed during the reaction between glucose and the glucose conjugated detection antibody was converted to a thermoelectric signal. • COMSOL Multiphysics simulations were performed to analyze the effect of fluid velocity ratio on the concentration profile the of the substrate. • Standard calibration curve was generated for synthetic TNF- α (0–2000 pg mL−1), y = 0.0315 × +2.5507, r = 0.9942. • The accuracy of the calorimetric platform was validated using conventional ELSA. [ABSTRACT FROM AUTHOR]