A Flexible Temperature Sensor Integrated at Needle Tip for In Situ Acupoint Temperature Monitoring.

Temperature can reflect vital activities, and researchers have attempted to guide Chinese medicine diagnosis and treatment by observing acupoint temperature changes. Integrating a temperature sensor at the needle tip enables in situ acupoint temperature measurement. However, the sensor needles for acupoint temperature monitoring designed in previous studies were fabricated by manually soldering thermistor beads and metal wires, making mass production difficult. In this work, using MEMS manufacturing technology, a flexible temperature sensor that can be integrated at the needle tip is proposed and can be mass-produced on silicon wafers. The sensor uses a Pt thermistor as the temperature-sensing element and has a slender flexible structure with dimensions of 125 µm width by 3.2 cm length. As the sensor is inserted into a hollow needle, the Pt thermistor is glued to the needle tip. In the temperature range of 30 °C to 50 °C, the fabricated temperature sensor has a sensitivity of 5.00 Ω∙°C-1, a nonlinearity of ±0.39%FS, and a repeatability error of ±2.62%FS. Additionally, the sensor has been applied to in vivo acupoint temperature monitoring experiments in rats and demonstrated good performance, suggesting its promise for future research on acupoint temperature.

Wave propagation in a light-temperature neural network under adaptive local energy balance.

External electric and mechanical stimuli can induce shape deformation in excitable media because of its intrinsic flexible property. When the signals propagation in the media is described by a neural network, creation of heterogeneity or defect is considered as the effect of shape deformation due to accumulation or release of energy in the media. In this paper, a temperature-light sensitive neuron model is developed from a nonlinear circuit composed of a phototube and a thermistor, and the physical energy is kept in capacitive and inductive terms. Furthermore, the Hamilton energy for this function neuron is obtained in theoretical way. A regular neural network is built on a square array by activating electric synapse between adjacent neurons, and a few of neurons in local area is excited by noisy disturbance, which induces local energy diversity, and continuous coupling enables energy propagation and diffusion. Initially, the Hamilton energy function for a temperature-light sensitive neuron can be obtained. Then, the finite neurons are applied noise to obtain energy diversity to explore the energy spread between neurons in the network. For keeping local energy balance, one intrinsic parameter is regulated adaptively until energy diversity in this local area is decreased greatly. Regular pattern formation indicates that local energy balance creates heterogeneity or defects and a few of neurons show continuous parameter shift for keeping energy balance in a local area, which supports gradient energy distribution for propagating waves in the network.

Design of a Negative Temperature Coefficient Temperature Measurement System Based on a Resistance Ratio Model.

In this paper, a temperature measurement system with NTC (Negative Temperature Coefficient) thermistors was designed. An MCU (Micro Control Unit) primarily operates by converting the voltage value collected by an ADC (Analog-to-Digital Converter) into the resistance value. The temperature value is then calculated, and a DAC (Digital-to-Analog Converter) outputs a current of 4 to 20 mA that is linearly related to the temperature value. The nonlinear characteristics of NTC thermistors pose a challenging problem. The nonlinear characteristics of NTC thermistors were to a great extent solved by using a resistance ratio model. The high precision of the NTC thermistor is obtained by fitting it with the Hoge equation. The results of actual measurements suggest that each module works properly, and the temperature measurement accuracy of 0.067 °C in the range from -40 °C to 120 °C has been achieved. The uncertainty of the output current is analyzed and calculated with the uncertainty of 0.0014 mA. This type of system has broad potential applications in industry fields such as the petrochemical industry.

Relationship Between Running Biomechanics and Core Temperature Across a Competitive Road Race.

BACKGROUND: Outdoor races introduce environmental stressors to runners, and core temperature changes may influence runners' movement patterns. This study assessed changes and determined relationships between sensor-derived running biomechanics and core temperature among runners across an 11.27-km road race. HYPOTHESIS: Core temperatures would increase significantly across the race, related to changes in spatiotemporal biomechanical measures. STUDY DESIGN: Cross-sectional cohort study. LEVEL OF EVIDENCE: Level 3. METHODS: Twenty runners (9 female, 11 male; age, 48 ± 12 years; height, 169.7 ± 9.1 cm; mass, 71.3 ± 13.4 kg) enrolled in the 2022 Falmouth Road Race were recruited. Participants used lightweight technologies (ingestible thermistors and wearable sensors) to monitor core temperature and running biomechanics throughout the race. Timestamps were used to align sensor-derived measures for 7 race segments. Observations were labeled as core temperatures generally within normal limits (<38°C) or at elevated core temperatures (≥38°C). Multivariate repeated measures analyses of variance were used to assess changes in sensor-derived measures across the race, with Bonferroni post hoc comparisons for significant findings. Pearson's r correlations were used to assess the relationship between running biomechanics and core temperature measures. RESULTS: Eighteen participants developed hyperthermic core temperatures (39.0°C ± 0.5°C); core temperatures increased significantly across the race (P < 0.01). Kinetic measures obtained from the accelerometers, including shock, impact, and braking g, all significantly increased across the race (P < 0.01); other sensor-derived biomechanical measures did not change significantly. Core temperatures were weakly associated with biomechanics (|r range|, 0.02-0.16). CONCLUSION: Core temperatures and kinetics increased significantly across a race, yet these outcomes were not strongly correlated. The observed kinetic changes may have been attributed to fatigue-related influences over the race. CLINICAL RELEVANCE: Clinicians may not expect changes in biomechanical movement patterns to signal thermal responses during outdoor running in a singular event.

Enhanced Thermal Stability and Broad Temperature Range in High-Entropy (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)NbO4 Ceramics.

Next-generation high-temperature applications increasingly rely heavily on advanced thermistor materials with enhanced thermal stability and electrical performance. However, thus far, the great challenge of realizing high thermal stability and precision in a wide temperature range has become a key bottleneck restricting the high-temperature application. Here, we propose a high-entropy strategy to design novel high-temperature thermistor ceramics (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)NbO4. Differences in atomic size, mass, and electronegativity in this high-entropy system cause high lattice distortion, substantial grain boundaries, and high dislocation density. These enhance the charge carrier transport and reduce the grain boundary resistance, thus synergistically broadening the temperature range. Our samples maintain high precision and thermal stability over a wide temperature range from room temperature to 1523 K (ΔT = 1250 K) with an aging value as low as 0.42% after 1000 h at 1173 K, showing breakthrough progress in high-temperature thermistor ceramics. This study establishes an effective approach to enhancing the performance of high-temperature thermistor materials through high-entropy strategies.

Flexible Copper-Based Thermistors Fabricated by Laser Direct Writing for Low-Temperature Sensing.

With the flexibilization tendency of traditional electronics, developing sensing devices for the low-temperature field is demanding. Here, we fabricated a flexible copper-based thermistor by a laser direct writing process with Cu ion precursors. The copper-based thermistor performs with excellent temperature sensing ability and high stability under different environments. We discussed the effect of laser power on the temperature sensitivity of the copper-based thermistor, explained the sensing mechanism of the as-written copper-based films, and fabricated a temperature sensor array for realizing temperature management in a specific zone. All of the investigations have demonstrated that such copper-based thermistors can be used as candidate devices for low-temperature sensing fields.

High-stability solid solution perovskite (1-x) Bi0.2Sr0.5La0.3TiO3- xLaMnO3 (0.05≤ × ≤0.2) for wide-temperature NTC thermistors.

The development of negative temperature coefficient (NTC) thermistor materials with a wide range of operating temperatures, high resistance (R), low thermal content (B) and good stability is significant for improving the overall performance of NTC thermistors. Traditional NTC thermistors materials are of the spinel, however, their practical applications are commonly limited to temperatures below approximately 200°C.In this study, it was found that a novel perovskite-structured solid solution (1-x)Bi0.2Sr0.5La0.3TiO3-xLaMnO3 (0.05 ≤ × ≤ 0.2) (BSLT-LM) showed good NTC performance from room temperature to high temperature (600°C) due to the stable structure at high temperatures. The ρ25, ρ100, ρ600 and B25/100, B25/600 constants of Bi0.2Sr0.5La0.3TiO3-0.1LaMnO3 NTC thermistors are approximately 1.76 × 108 Ω cm, 1.13 × 107 Ω cm, 9.89 × 102 Ω cm, 4063.91 K, 5472.34 K, respectively. The electrical conductivity of these solid solution refers to the electronic transition between Mn3+ and Mn4+, and oxygen vacancies. These results demonstrate the tremendous potential of perovskite-structured (1-x) Bi0.3Sr0.5La0.2TiO3-xLaMnO3 thermistor ceramics with NTC performance.

Exploring Pyrrolo-Phenanthrolines as Semiconductors for Potential Implementation in Organic Electronics.

This paper describes the synthesis and characterization of new organic semiconductors based on pyrrolo[1,2-i][1,7]phenanthrolines in the form of thin layers. The thin layers, produced via the spin coating method (with a thickness of 10-11 µm), were investigated for their electrical and optical properties. After heat treatment at temperatures ranging from 210 to 240 °C, the layers displayed consistent and reproducible properties. The layers exhibited n-type semiconductor behavior, with a thermal activation energy (Ea) in the range of 0.75-0.78 eV. Additionally, the layers showed transmittance values of 84-92% in the visible and near-infrared spectral ranges, with a direct optical band gap (Egod) ranging from 3.13 to 4.11 eV. These thin layers have potential applications in electronic devices such as thermistors, as well as in nanoelectronics and optoelectronics. Overall, these new organic semiconductors show promising properties for practical implementation in various electronic applications.

Estimating inputs for dispersion modeling in mobile platform applications.

Mobile monitoring platforms (MMP) are popular in air quality studies. One application of MMP is in estimating pollutant emissions from area sources. The MMP is used to measure concentrations of the relevant species at several locations around the area source, while the associated meteorological information is measured at the same time. Emissions from the area source are inferred by fitting the measured concentrations to estimates from dispersion models. These models require meteorological inputs, such as the kinematic heat flux and the surface friction velocity, that are best computed with measurements of time resolved velocity and temperature made with 3-D sonic anemometers. Because the setting up and dismantling of a 3-D sonic anemometer is not compatible with the necessary mobility of the MMP, it is useful to use alternative instrumentation and methods that provide accurate estimates of these inputs. In this study, we demonstrate such a method based on measurements of horizontal wind speed and temperature fluctuations at a single height. The method was evaluated by comparing methane emissions from a dairy manure lagoon inferred from a dispersion model that uses modeled meteorological inputs to those inferred from measurements with 3-D sonic anemometers. The emission estimates from the modeled meteorological inputs were close to those based on measurements made with 3-D sonic anemometers. We then demonstrate how this approach can be adapted for mobile platform applications by showing that winds measured using a 2-D sonic anemometer and temperature fluctuations measured with a bead thermistor, which can all be carried or mounted on a MMP, yields results that are close to those from a 3-D sonic anemometer.

Formation and Properties of Thermistor Chips Based on Semiconductor 3D Metal Oxide Films Obtained by RF-Magnetron Sputtering.

The formation of oxide semiconductor films of the (Mn,Co,Cu)3O4 type by radio frequency magnetron sputtering is presented. The conditions of deposition and subsequent heat treatment make it possible to obtain films with electrophysical characteristics close to those of the bulk ceramic materials used as a target for magnetron sputtering. Two variants of thermistor geometry were implemented. In the first case, the working layer of oxide semiconductor was deposited directly on the dielectric substrate (planar geometry), and in the second case on the layer with high electrical conductivity (Ni or Al) forming the inner electrode (layered geometry). The lower limit of the nominal resistance of the planar thermistor while maintaining high temperature nonlinearity is ~ 10 kΩ. The layered structure with the inner electrode makes it possible to reduce the lower limit of resistance up to ~ 50 Ω without losing the temperature nonlinearity of the thermistor. In addition, heat treatment above 450 °C or current self-heating with sufficient power output leads to the appearance of a pronounced voltage nonlinearity, which increases the thermal constant B of thermistors from 2400-3400 to 5000-5500 K. The fields of application of oxide-film structures for the correction of linear resistors and the implementation of integration approaches in the construction of linearized sensors are discussed.

Hydrogen Sensor Based on NTC Thermistor with Pt-Loaded WO3/SiO2 Coating.

A novel hydrogen sensor based on a negative temperature coefficient (NTC) thermistor with Pt-loaded WO3/SiO2 coating is proposed and demonstrated experimentally. When the Pt-loaded WO3/SiO2 film is exposed to the mixture of air and H2, the exothermic reactions caused by hydrogen and WO3 with the cooperation of the Pt catalyst raise the local temperature of the NTC thermistor and lower its resistance. Hence, hydrogen concentration can be measured by monitoring the voltage across the NTC thermistor in a series circuit. The proposed device has a rapid response time, high sensitivity, and excellent repeatability to hydrogen as well as immunity to humidity, a compact size, a low manufacturing cost, and is easy to use.

Impact of Various Thermistors on the Properties of Resistive Microbolometers Fabricated by CMOS Process.

Microbolometers based on the CMOS process has the important advantage of being automatically merged with circuits in the fabrication of larger arrays, but they typically suffer from low detectivity due to the difficulty in realizing high-sensitivity thermistors in the CMOS process. In this paper, two resistive microbolometers based on polysilicon and metal Al thermistors, respectively, are designed and fabricated by the standard CMOS process. Experimental results show that the detectivity of the two resistive microbolometers can reach a maximum of 1.78 ´ 109 cmHz1/2/W at 25 µA and a maximum of 6.2 ´ 108 cmHz1/2/W at 267 µA. The polysilicon microbolometer exhibits better detectivity at lower bias current due to its lower effective thermal conductivity and larger resistance. Even though the thermal time constant of the polysilicon thermistor is three times slower than that of the metal Al thermistor, the former is more suitable for designing a thermal imaging system with sensitive and low power consumption.

A SiCN Thin Film Thermistor Based on DVB Modified Polymer-Derived Ceramics.

Carbon-rich SiCN ceramics were prepared by divinylbenzene (DVB)-modified polysilazane (PSN2), and a high-conductivity SiCN thin film sensor suitable for medium-low temperature sensing was fabricated. The modified liquid precursors were patterned by direct ink writing to produce SiCN resistive grids with line widths of several hundreds of micrometers and thicknesses of several micrometers. The introduction of DVB not only increases the critical thickness of SiCN ceramics several times, but also significantly improves the conductivity of SiCN, making it meet the conductivity requirements of sensing applications in the mid-low temperature range. The electrical conductivity and microstructure of DVB-modified SiCN ceramics were studied in detail. In the temperature range of 30~400 °C, the temperature resistance performance of DVB modified SiCN resistance grid was measured. The SiCN ceramics with low DVB content not only have excellent electrical conductivity, but also have good oxidation resistance.

Nasal cannula use during polysomnography in children aged under three with suspected sleep apnea.

OBJECTIVE: Early diagnosis of obstructive sleep apnea (OSA) in children is important. The use of a nasal cannula as an airflow sensor during polysomnography has not been evaluated in younger children. The study aims to evaluate the use of nasal cannula in detecting respiratory events in children under three with suspected OSA during daytime nap studies. METHODS: A total of 185 patients were prospectively included. Respiratory events were scored using nasal cannula alone, thermistor alone, and both methods simultaneously as the airflow sensor. Agreement and diagnostic accuracy were assessed. RESULTS: One hundred and seventy-two children were finally analyzed and 110 (64.0%) presented OSA. Total sleep time with an uninterpretable signal was longer with the nasal cannula than with the thermistor (17.8% vs 1.9%; p < 0.001), and was associated with poor sensor tolerance and adenotonsillar hypertrophy. In the estimation of the apnea-hypopnea index, the nasal cannula showed lower agreement than the thermistor with the joint use of the two sensors (intraclass correlation coefficient: 0.79 vs 0.996 with thermistor). Compared with the thermistor, the nasal cannula presented lower sensitivity for detecting OSA (82.7% vs 95.5%) and a lower negative predictive value (76.5% vs 92.4%). Overall, fewer children were diagnosed with severe OSA with the nasal cannula (19.8% vs 30.8% with the thermistor, and 32.6% with both). CONCLUSIONS: In children under the age of three, the ability of the nasal cannula to detect obstructive events was relatively low. Therefore, other non-invasive measurements for identifying respiratory events during sleep may be of additional value.

Responsivity and NEP Improvement of Terahertz Microbolometer by High-Impedance Antenna.

The antenna-coupled microbolometer with suspended titanium heater and thermistor was attractive as a terahertz (THz) detector due to its structural simplicity and low noise levels. In this study, we attempted to improve the responsivity and noise-equivalent power (NEP) of the THz detector by using high-resistance heater stacked on the meander thermistor. A wide range of heater resistances were prepared by changing the heater width and thickness. It was revealed that the electrical responsivity and NEP could be improved by increasing the heater's resistance. To make the best use of this improvement, a high-impedance folded dipole antenna was introduced, and the optical performance at 1 THz was found to be better than that of the conventional halfwave dipole antenna combined with a low-resistance heater. Both the electrical and optical measurement results indicated that the increase in heater resistance could reduce the thermal conductance in the detector, thus improved the responsivity and NEP even if the thermistor resistance was kept the same.

Application and comparison of thermistors and fiber optic temperature sensor reference for ILP measurement of magnetic fluids in double cell magnetic hyperthermia.

One of the simplest way to characterize the heating efficiency of magnetic fluids used in hyperthermia treatment is the calorimetric measurement of the specific loss power with direct temperature detection. However, the performance of metallic sensors in an alternating magnetic field is degraded by the self-heating of the probes, and electromagnetic interference can be also significant. In our double cell differential thermometric system these disturbing effects can be compensated. Specific loss power measurements of EMG700 magnetic fluid with negative temperature coefficient thermistors in differential configuration are presented, and control measurements were performed with an optical fiber thermometer in f = 470 kHz - 1020 kHz frequency and H = 0.13 kA m - 1 - 1.19 kA m - 1 magnetic field strength range. We found that the specific loss power is proportional to the frequency and shows a quadratic dependence on the field strength in the low field strength region, therefore we calculated the intrinsic loss power of the fluid from the measured specific loss power. At this field conditions intrinsic loss power up to 0.53 nH m 2 kg - 1 was determined.

One-Dimensional Systemic Modeling of Thermal Sensors Based on Miniature Bead-Type Thermistors.

Accurate measurements of thermal properties is a major concern, for both scientists and the industry. The complexity and diversity of current and future demands (biomedical applications, HVAC, smart buildings, climate change adapted cities, etc.) require making the thermal characterization methods used in laboratory more accessible and portable, by miniaturizing, automating, and connecting them. Designing new materials with innovative thermal properties or studying the thermal properties of biological tissues often require the use of miniaturized and non-invasive sensors, capable of accurately measuring the thermal properties of small quantities of materials. In this context, miniature electro-thermal resistive sensors are particularly well suited, in both material science and biomedical instrumentation, both in vitro and in vivo. This paper presents a one-dimensional (1D) electro-thermal systemic modeling of miniature thermistor bead-type sensors. A Godunov-SPICE discretization scheme is introduced, which allows for very efficient modeling of the entire system (control and signal processing circuits, sensors, and materials to be characterized) in a single workspace. The present modeling is applied to the thermal characterization of different biocompatible liquids (glycerol, water, and glycerol-water mixtures) using a miniature bead-type thermistor. The numerical results are in very good agreement with the experimental ones, demonstrating the relevance of the present modeling. A new quasi-absolute thermal characterization method is then reported and discussed. The multi-physics modeling described in this paper could in the future greatly contribute to the development of new portable instrumental approaches.

High Channel Temperature Mapping Electronics in a Thin, Soft, Wireless Format for Non-Invasive Body Thermal Analysis.

Hemodynamic status has been perceived as an important diagnostic value as fundamental physiological health conditions, including decisive signs of fatal diseases like arteriosclerosis, can be diagnosed by monitoring it. Currently, the conventional hemodynamic monitoring methods highly rely on imaging techniques requiring inconveniently large numbers of operation procedures and equipment for mapping and with a high risk of radiation exposure. Herein, an ultra-thin, noninvasive, and flexible electronic skin (e-skin) hemodynamic monitoring system based on the thermal properties of blood vessels underneath the epidermis that can be portably attached to the skin for operation is introduced. Through a series of thermal sensors, the temperatures of each subsection of the arrayed sensors are observed in real-time, and the measurements are transmitted and displayed on the screen of an external device wirelessly through a Bluetooth module using a graphical user interface (GUI). The degrees of the thermal property of subsections are indicated with a spectrum of colors that specify the hemodynamic status of the target vessel. In addition, as the sensors are installed on a soft substrate, they can operate under twisting and bending without any malfunction. These characteristics of e-skin sensors exhibit great potential in wearable and portable diagnostics including point-of-care (POC) devices.

Aquatic Ecosystems of the Anthropocene: Limnology and Microbial Ecology of Mine Pit Lakes.

Mine pit lakes ('pit lakes') are new aquatic ecosystems of the Anthropocene. Potentially hundreds of meters deep, these lakes are prominent in the landscape and in the public consciousness. However, the ecology of pit lakes is underrepresented in the literature. The broad goal of this research was to determine the environmental drivers of pelagic microbe assemblages in Australian coal pit lakes. The overall experimental design was four lakes sampled three times, top and bottom, in 2019. Instrument chains were installed in lakes and measurements of in situ water quality and water samples for metals, metalloids, nutrients and microbe assemblage were collected. Lakes were monomictic and the timing of mixing was influenced by high rainfall events. Water quality and microbial assemblages varied significantly across space and time, and most taxa were rare. Lakes were moderately saline and circumneutral; Archeans were not prevalent. Richness also varied by catchment. Microbial assemblages correlated to environmental variables, and no one variable was consistently significant, spatially or temporally. Study lakes were dominated by 'core' taxa exhibiting temporal turnover likely driven by geography, water quality and interspecific competition, and the presence of water chemistry associated with an artificial aquifer likely influenced microbial community composition. Pit lakes are deceptively complex aquatic ecosystems that host equally complex pelagic microbial communities. This research established links between microbial assemblages and environmental variables in pit lakes and determined core communities; the first steps towards developing a monitoring program using microbes.

Electrospun Nickel Manganite (NiMn2O4) Nanocrystalline Fibers for Humidity and Temperature Sensing.

Nickel manganite nanocrystalline fibers were obtained by electrospinning and subsequent calcination at 400 °C. As-spun fibers were characterized by TG/DTA, Scanning Electron Microscopy and FT-IR spectroscopy analysis. X-ray diffraction and FT-IR spectroscopy analysis confirmed the formation of nickel manganite with a cubic spinel structure, while N2 physisorption at 77 K enabled determination of the BET specific surface area as 25.3 m2/g and (BJH) mesopore volume as 21.5 m2/g. The material constant (B) of the nanocrystalline nickel manganite fibers applied by drop-casting on test interdigitated electrodes on alumina substrate, dried at room temperature, was determined as 4379 K in the 20-50 °C temperature range and a temperature sensitivity of -4.95%/K at room temperature (25 °C). The change of impedance with relative humidity was monitored at 25 and 50 °C for a relative humidity (RH) change of 40 to 90% in the 42 Hzπ1 MHz frequency range. At 100 Hz and 25 °C, the sensitivity of 327.36 ± 80.12 kΩ/%RH was determined, showing that nickel manganite obtained by electrospinning has potential as a multifunctional material for combined humidity and temperature sensing.