Planar Thermoelectric Microgenerators in Application to Power RFID Tags

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.

Additive Manufacturing of Thermoelectric Microdevices for 4D Thermometry

Thermometry, the process of measuring temperature, is one of the most fundamental tasks not only for understanding the thermodynamics of basic physical, chemical, and biological processes but also for thermal management of microelectronics. However, it is a challenge to acquire microscale temperature fields in both space and time. Here, a 3D printed micro-thermoelectric device that enables direct 4D (3D Space + Time) thermometry at the microscale is reported. The device is composed of freestanding thermocouple probe networks, fabricated by bi-metal 3D printing with an outstanding spatial resolution of a few µm. It shows that the developed 4D thermometry can explore dynamics of Joule heating or evaporative cooling on microscale subjects of interest such as a microelectrode or a water meniscus. The utilization of 3D printing further opens up the possibility to freely realize a wide range of on-chip, freestanding microsensors or microelectronic devices without the design restrictions by manufacturing processes.

Comparative Evaluations on Real-Time Monitoring of Temperature Sensors during Endoscopic Laser Application

Temperature sensors, such as Fiber Bragg Grating (FBG) and thermocouple (TC), have been widely used for monitoring the interstitial tissue temperature during laser irradiation. The aim of the current study was to compare the performance of both FBG and TC in real-time temperature monitoring during endoscopic and circumferential laser treatment on tubular tissue structure. A 600-µm core-diameter diffusing applicator was employed to deliver 980-nm laser light (30 W for 90 s) circumferentially for quantitative evaluation. The tip of the TC was covered with a white tube (W-TC) in order to prevent direct light absorption and to minimize temperature overestimation. The temperature measurements in air demonstrated that the measurement difference in the temperature elevations was around 3.5 °C between FBG and W-TC. Ex vivo porcine liver tests confirmed that the measurement difference became lower (less than 1 °C). Ex vivo porcine esophageal tissue using a balloon-integrated catheter exhibited that both FBG and W-TC consistently showed a comparable trend of temperature measurements during laser irradiation (~2 °C). The current study demonstrated that the white tube-covered TC could be a feasible sensor to monitor interstitial tissue temperature with minimal overestimation during endoscopic laser irradiation. Further in vivo studies on gastroesophageal reflux disease will investigate the performance of the W-TC to monitor the temperature of the esophageal mucosa surface in real-time mode to warrant the safety of endoscopic laser treatment.

Dynamic Characterization of Thermocouples under Double-Pulse Laser-Induced Thermal Excitation

This study investigated the dynamic characteristics of thermocouples by using double-pulse laser excitation for dynamic temperature calibration under extreme conditions. An experimental device was constructed for double-pulse laser calibration; the device uses a digital pulse delay trigger to precisely control the double-pulse laser to achieve sub-microsecond dual temperature excitation with adjustable time intervals. The time constants of thermocouples under single-pulse laser excitation and double-pulse laser excitation were evaluated. In addition, the variation trends of thermocouple time constants under different double-pulse laser time intervals were analyzed. The experimental results indicated that the time constant increases and then decreases with the decrease in the time interval of the double-pulse laser. A method for dynamic temperature calibration was established for the evaluation of the dynamic characteristics of temperature sensors.

A Flexible Thermocouple Film Sensor for Respiratory Monitoring

A novel flexible thermocouple film sensor on a polyimide substrate is proposed that is simple and flexible for monitoring the respiratory signal. Several thermocouples were connected in series and patterned on the polyimide substrate, and each one is formed by copper and a constant line connected to each other at two nodes. The respiratory signal was measured by the output voltage, which resulted from the temperature difference between the hot and cold junctions. The sensors were fabricated with surface-microfabrication technology with three sputtering steps. The measurement results showed that the peak voltage decreased by 90% in the case of apnea compared with normal breathing. The sensor has potential application for wearable detection of sleep apnea hypopnea syndrome (OSAHS).

Superior Thermoelectric Performance of Robust Column-Layer ITO Thin Films Tuning by Profuse Interfaces

Indium tin oxide (ITO) thin films suffer from poor chemical stability at high temperatures because of the instability of point defects and structural variations. An interface design strategy was proposed herein to improve this situation, where a robust ITO-based thin film with a column-layer structure was fabricated. Three types of column-layer ITO thin films were fabricated via magnetron sputtering. By tuning the interfaces, we controlled the effective mass and weighted mobility, enhancing the electrical conductivity (2.17 × 10⁶ S m^-1) and power factor (1138 μW m^-1 K^-2). The crack propagation path was prolonged because of the profuse interfaces between the columns and layers in the alternate thin films. Thus, enhanced nanohardness (16.5 GPa) was obtained. The structural evolution and performance of the column-layer ITO thin films annealed under different conditions were investigated. The atoms were restricted by the profuse interfaces, resulting in high-temperature stability. The results demonstrate that the interface design of ITO thin films can efficiently modify the stability of conductive ceramics over a wide temperature range, which has significant potential for applications in microdevices and aero engines.

Thermoelectric Energy Micro Harvesters with Temperature Sensors Manufactured Utilizing the CMOS-MEMS Technique

This study develops a TEMH (thermoelectric energy micro harvester) chip utilizing a commercial 0.18 μm CMOS (complementary metal oxide semiconductor) process. The chip contains a TEMH and temperature sensors. The TEMH is established using a series of 54 thermocouples. The use of the temperature sensors monitors the temperature of the thermocouples. One temperature sensor is set near the cold part of the thermocouples, and the other is set near the hot part of the thermocouples. The performance of the TEMH relies on the TD (temperature difference) at the CHP (cold and hot parts) of the thermocouples. The more the TD at the CHP of the thermocouples increases, the higher the output voltage and output power of the TEMH become. To obtain a higher TD, the cold part of the thermocouples is designed as a suspended structure and is combined with cooling sheets to increase heat dissipation. The cooling sheet is constructed of a stack of aluminum layers and is mounted above the cold part of the thermocouple. A finite element method software, ANSYS, is utilized to compute the temperature distribution of the TEMH. The TEMH requires a post-process to obtain the suspended thermocouple structure. The post-process utilizes an RIE (reactive ion etch) to etch the two sacrificial materials, which are silicon dioxide and silicon substrate. The results reveal that the structure of the thermocouples is completely suspended and does not show any injury. The measured results reveal that the output voltage of the TEMH is 32.5 mV when the TD between the CHP of the thermocouples is 4 K. The TEMH has a voltage factor of 8.93 mV/mm²K. When the TD between the CHP of the thermocouples is 4 K, the maximum output power of the TEMH is 4.67 nW. The TEMH has a power factor of 0.31 nW/mm²K².

Thermal Characterization of a Gas Foil Bearing-A Novel Method of Experimental Identification of the Temperature Field Based on Integrated Thermocouples Measurements

Maintenance of adequate thermal properties is critical for correct operation of a gas foil bearing. In this work, the authors present the results of the experimentally conducted thermal characterization of a prototype installation of the bearing. A novel method of temperature identification, based on integrated thermocouples readings, has been employed to determine the thermal properties of the specialized sensing top foil mounted in the tested bearing. Two measurement campaigns have been subsequently completed, applying freely-suspended and two-node support configurations, to gather complementary knowledge regarding the bearing's operation. Apart from the rotational speed and temperature field measurements, the authors have also studied the friction torque and the shaft's journal trajectories based on its radial displacements. The temporal courses for the above-mentioned quantities have enabled inference on the effects present during run-up, run-out and stable state operation at a constant speed. As confirmed, the applied distribution of the integrated sensors allows for temperature readings on the entire outer surface of the foil, and therefore, provides useful data for the bearing characterization. The work is concluded with presentation of the recommended directions regarding future improvements of the proposed measurement technique and more comprehensive study of the bearing's characteristics.

Easy as piadcs: A low-cost, ultra-high-resolution data acquisition system using a Raspberry Pi

PREMISE

High-precision data acquisition (DAQ) is essential for developing new methods in the plant sciences. Commercial high-resolution DAQ systems are cost prohibitive, whereas the less expensive systems that are currently available lack the resolution and precision required for many physiological measurements.

METHODS AND RESULTS

We developed the software libraries, called piadcs, and hardware design for a DAQ system based on an ultra-high-resolution analog-to-digital converter and a Raspberry Pi computer. We tested the system precision with and without a thermocouple attached and found the precision with the sensor to be better than ±0.01°C and the maximum possible system resolution to be 0.4 ppm.

CONCLUSIONS

The ultra-high-resolution DAQ system described here is inexpensive, flexible enough to be used with many different sensors, and can be built by researchers with rudimentary electronic and computer skills. This system is most applicable in the development of new measurement techniques and the improvement of existing methods.

Paper-Based Ionic Thermocouples for Inexpensive and High-Precision Measurement of Temperature

Accurate and yet cost-effective temperature measurements are required in various sectors of academia and industry. Thermocouples (TCs) are most widely used for temperature measurements; however, their low temperature sensitivity and high thermal conductivity should be improved to ensure the reliable measurement of output voltage for small temperature differences. To address this, a paper-based ionic thermocouple (P-iTC) presented here utilizes a pair of paper strips soaked with the electrolytes of potassium ferri-/ferrocyanide and iron (II/III) chloride redox couples, which are used as p- and n-type elements, respectively. The fabricated P-iTC provides 70× higher temperature sensitivity (α, 2.8 mV/K) and 30× lower thermal conductivity (k, 0.8 W/m K) than those of commercial K-type TCs, thereby yielding a remarkably high α/k ratio of 3.5 mV m/W. Reliable sensing performance is measured during three weeks of operation, which indicates that the P-iTC should be stable in long-term operation. To demonstrate the practicality of the P-iTC, a 3 × 3 planar array of P-iTCs is fabricated to monitor the temperature profile of a surface in contact with heat sources. Using pencil-drawn graphite electrodes on paper, a highly cost-effective P-iTC with the material cost of ∼0.5 cents per device is also fabricated, which is successfully used to monitor cold chain temperatures while retaining its excellent temperature-sensing performance.

Observations on the Changing Shape of the Ice Mass and the Determination of the Sublimation End Point in Freeze-Drying: An Application for Through-Vial Impedance Spectroscopy (TVIS)

Models for ice sublimation from a freeze-drying vial rely on the assumption of a planar ice interface up to ~25% loss of ice mass (which is difficult to qualify) whereas single-vial determinations of the sublimation endpoint (by temperature sensors) are based on the point when the observed temperature reaches a plateau, which cannot differentiate between sublimation and desorption-drying. In this work, the real part capacitance of TVIS vial(s) containing frozen water (during sublimation drying) was measured at 100 kHz. This parameter C′(100 kHz) was shown to be highly sensitive to the shape and volume of the ice mass and is therefore a useful parameter for monitoring ice sublimation. By placing a digital camera in front of an isolated TVIS vial containing ice, it was possible to relate the changes in the shape of the ice mass with the changes in the trajectory of the time profile of C′(100 kHz) and determine the point of deviation from a planar ice interface and ultimately determine the point when the last vestiges of ice disappear. Thereafter, the same characteristics of the C′(100 kHz) time-profile were identified for those TVIS vials located out of sight of the camera in a separate full-shelf lyo study, thereby obviating the need for photographic examination.

Modified Thermocouple Sensor and External Reference Junction Enhance Accuracy in Indoor Air Temperature Measurements

Indoor air temperature belongs to the most important climatic variables in indoor climate research, affecting thermal comfort, energy balance, and air movement in buildings. This paper focuses on measurement errors when using thermocouples in indoor temperature measurements, with special attention on measurements of air temperature. We briefly discuss errors in thermocouple measurements, noting that, for temperatures restricted to indoor temperature ranges, a thermocouple Type T performs much better than stated in "standards". When thermocouples are described in the literature, industrial applications are primarily considered, involving temperatures up to several hundred degrees and with moderate demands on accuracy. In indoor applications, the temperature difference between the measuring and the reference junction is often only a few degrees. Thus, the error contribution from the thermocouple itself is almost immeasurable, while the dominant error source is in the internal reference temperature compensation in the measuring instrument. It was shown that using an external reference junction can decrease the measurement error substantially (i.e., down to a few hundredths of a degree) in room temperature measurements. One example of how such a device may be assembled is provided. A special application of room temperature measurements involves measuring indoor air temperature. Here, errors, due to radiation influence on the sensor from surrounding surfaces, were surprisingly high. The means to estimate the radiative influence on typical thermocouples are presented, along with suggestions for modification of thermocouple sensors to lower the radiation impact and thereby improve the measurement accuracy.

Design and Fabrication of a Low-Cost Thermopile Infrared Detector

In this paper, we design and optimize a low-cost, closed-film structure of a microelectromechanical systems (MEMS) thermopile infrared detector. By optimizing the circular arrangement of thermocouple strips and the thermal isolation design of the cold end to pursue a higher temperature difference, in addition to eliminating the absorption region, silicon nitride is deposited on the whole device surface as a passivated absorption layer. This reduces the cost while maintaining the voltage response and is suitable for mass production. The optimized detector had a 22.6% improvement in the response rate to 34.2 V/W, a detection rate of 1.02 × 10⁸ cm·Hz^1/2/W, and a response time of 26.9 ms. The design optimization of this detector provides a reference for further development of IR detectors.

Dead or "undead"? The curious and untidy history of Volta's concept of "contact potential"

Much of the long controversy concerning the workings of electric batteries revolved around the concept of the contact potential (especially between different types of metals), originated by Alessandro Volta in the late eighteenth century. Although Volta's original theory of batteries has been thoroughly rejected and most discussions in today's electrochemistry hardly ever mention the contact potential, the concept has made repeated comebacks through the years, and has by no means completely disappeared. In this paper, I describe four salient foci of its revivals: dry piles, thermocouples, quadrant electrometers, and vacuum phenomena. I also show how the contact potential has maintained its presence in some cogent modern scientific literature. Why has the death of the Voltaic contact potential been such an untidy affair? I suggest that this is because the concept has displayed significant meaning and utility in various experimental and theoretical contexts, but has never been successfully given a simple, unified account. Considering that situation, I also suggest that it would make sense to preserve and develop it as a multifarious concept.

Multi-Point Flexible Temperature Sensor Array and Thermoelectric Generator Made from Copper-Coated Textiles

The integration of electrical functionality into flexible textile structures requires the development of new concepts for flexible conductive material. Conductive and flexible thin films can be generated on non-conductive textile materials by electroless metal deposition. By electroless copper deposition on lyocell-type cellulose fabrics, thin conductive layers with a thickness of approximately 260 nm were prepared. The total copper content of a textile fabric was analyzed to be 147 mg per g of fabric, so that the textile character of the material remains unchanged, which includes, for example, the flexibility and bendability. The flexible material could be used to manufacture a thermoelectric sensor array and generator. This approach enables the formation of a sensor textile with a large number of individual sensors and, at the same time, a reduction in the number of electrical connections, since the conductive textile serves as a common conductive line for all sensors. In combination with aluminum, thermoelectric coefficients of 3–4 µV/K were obtained, which are comparable with copper/aluminum foil and bulk material. Thermoelectric generators, consisting of six junctions using the same material combinations, led to electric output voltages of 0.4 mV for both setups at a temperature difference of 71 K. The results demonstrate the potential of electroless deposition for the production of thin-film-coated flexible textiles, and represent a key technology to achieve the direct integration of electrical sensors and conductors in non-conductive material.

Gas-Phase Temperature Mapping of Evaporating Microdroplets

Evaporation is a ubiquitous and complex phenomenon of importance to many natural and industrial systems. Evaporation occurs when molecules near the free interface overcome intermolecular attractions with the bulk liquid. As molecules escape the liquid phase, heat is removed, causing evaporative cooling. The influence of evaporative cooling on inducing a temperature difference with the surrounding atmosphere as well as within the liquid is poorly understood. Here, we develop a technique to overcome past difficulties encountered during the study of heterogeneous droplet evaporation by coupling a piezo-driven droplet generation mechanism to a controlled micro-thermocouple to probe microdroplet evaporation. The technique allowed us to probe the gas-phase temperature distribution using a micro-thermocouple (50 μm) in the vicinity of the liquid-vapor interface with high spatial (±10 μm) and temporal (±100 ms) resolution. We experimentally map the temperature gradient formed surrounding sessile water droplets having varying curvature dictated by the apparent advancing contact angle (100° ≲ θ ≲ 165°). The experiments were carried out at temperatures below and above ambient for a range of fixed droplet radii (130 μm ≲ R ≲ 330 μm). Our results provide a primary validation of the centuries-old theoretical framework underpinning heterogeneous droplet evaporation mediated by the working fluid, substrate, and gas thermophysical properties, droplet apparent contact angle, and droplet size. We show that microscale droplets residing on low-thermal-conductivity substrates such as glass absorb up to 8× more heat from the surrounding gas compared to droplets residing on high-thermal-conductivity substrates such as copper. Our work not only develops an experimental understanding of the heat transfer mechanisms governing droplet evaporation but also presents a powerful platform for the study and characterization of liquid-vapor transport at curved interfaces wetting and nonwetting advanced functional surfaces.

Temperature and time variations during apical resection

OBJECTIVE

The aim of this study was to investigate temperature and time variations during root-end resection.

MATERIAL AND METHODS

Sixty human premolars were selected. The root canals were enlarged up to ProTaper X3 rotary instrument. A thermocouple was placed into the root canal 1 mm behind the resection line. The teeth were randomly divided into six groups according to the apical resection method: steel bur, tungsten carbide bur, Lindeman bur, diamond bur, laser and ultrasonic surgical piezo with a diamond tip. The root ends were resected 3 mm away from the root apex. The temperature of the root dentine during resection was recorded as maximum temperature, mean temperature and temperature change. The time required for apicectomy was recorded for each group. The Kruskal-Wallis method was used to analyse the differences between temperature changes during apical resections. The significance level was set at 5%.

RESULTS

There was no significant difference between bur groups in terms of temperature increase. The maximum temperature in piezo surgery was significantly higher than the Lindeman, tungsten and steel burs (p < .001). In addition, the maximum temperature in laser surgery was higher than the Lindeman bur (p < .05). An increase in the temperature was mostly seen in piezo surgery and the least temperature change occurred in the Lindeman bur. Mean time stayed under 1 min in each group.

CONCLUSIONS

Although piezo caused the highest temperature increase, the measured temperature increase was within physiological limits in all tested techniques.

An Investigation on High-Resolution Temperature Measurement in Precision Fly-Cutting

The loads acting on a workpiece during machining processes determine the modification of the surface of the final workpiece and, thus, its functional properties. In this work, a method that uses thermocouples to measure the temperature in precision fly-cutting machining with high spatial and temporal resolution is presented. Experiments were conducted for various materials and machining parameters. We compare experimental measurement data with results from modern and advanced machining process simulation and find a good match between experimental and simulation results. Therefore, the simulation is validated by experimental data and can be used to calculate realistic internal loads of machining processes.

Development of a New Drill Design to Improve the Temperature Control during the Osteotomy for Dental Implants: A Comparative In Vitro Analysis

The present in vitro study evaluated a new drill design to improve the temperature control during the osteotomies for dental implant installation, comparing with two drill designs that use conventional external irrigation. Three blocks of synthetic cortical bone were used for osteotomy procedures. Three groups were created: control group 1 (Con1), where a conical multiple drill system with a conventional external irrigation system was used; control group 2 (Con2), where a single bur with a conventional external irrigation system was used; and, test group (Test), where the new single bur (turbo drill) with a new irrigation system was used. Twenty osteotomies were made without irrigation and with intense irrigation, for each group. A thermocouple was used to measure the temperature produced during the osteotomies. The measured temperature were: 28.9 ± 1.68 °C for group Con1; 27.5 ± 1.32 °C for group Con2; 26.3 ± 1.28 °C for group Test. Whereas, the measured temperatures with irrigation were: 23.1 ± 1.27 °C for group Con1; 21.7 ± 1.36 °C for group Con2; 19.4 ± 1.29 °C for group Test. The single drill with a new design for improving the irrigation and temperature control, in comparison with the drill designs with conventional external irrigation.

Thermal and Photo Sensing Capabilities of Mono- and Few-Layer Thick Transition Metal Dichalcogenides

Two-dimensional (2D) materials have shown promise in various optical and electrical applications. Among these materials, semiconducting transition metal dichalcogenides (TMDs) have been heavily studied recently for their photodetection and thermoelectric properties. The recent progress in fabrication, defect engineering, doping, and heterostructure design has shown vast improvements in response time and sensitivity, which can be applied to both contact-based (thermocouple), and non-contact (photodetector) thermal sensing applications. These improvements have allowed the possibility of cost-effective and tunable thermal sensors for novel applications, such as broadband photodetectors, ultrafast detectors, and high thermoelectric figures of merit. In this review, we summarize the properties arisen in works that focus on the respective qualities of TMD-based photodetectors and thermocouples, with a focus on their optical, electrical, and thermoelectric capabilities for using them in sensing and detection.

Influence of an 810-nm Diode Laser on the Temperature Changes of the External Root Surface: An In Vitro Study

Background and Aims:

Rising effects of temperature due to laser use during root canal disinfection may harm periodontium and alveolar bone. Therefore, the aim of this study was to estimate the surface root temperature of lower incisors throughout the application of different power levels and times of an 810-nm diode laser.

Materials and Methods:

Sixty single-rooted extracted human lower incisor teeth were selected and chemomechanical preparation was performed. Specimens were irradiated using 810-nm diode laser at 1.05, 1.5, and 1.95 W power settings and two periods of time 20 and 60s, in a continuous wave (CW) mode, without water spray. Specimens were divided into three main groups (n = 20). Each group was subdivided into two subgroups (n = 10). Then, the peak temperatures at the middle and apical regions of the root surface were registered using a thermocouple.

Results:

Temperature rise of root surface at all the selected output powers was below 7°C. The highest temperature value was obtained in the apical region at 60s when the root canal irradiated at 1.95 W output power.

Conclusion:

Diode laser is safe for use as a root canal disinfectant. Time of exposure to laser irradiation has an effect on the temperature difference at different output powers.

Thermal effect of Er:YAG and Er,Cr:YSGG used for debonding ceramic and metal orthodontic brackets: An experimental analysis

BACKGROUND

In orthodontics, erbium (Er:YAG) lasers can be used for bracket debonding.

OBJECTIVES

To assess the changes in temperature of pulp and enamel during laser debonding of brackets.

MATERIAL AND METHODS

A total of 13 brackets (n = 13; 2 metal and 11 ceramic brackets) were bonded to 13 caries-free premolars extracted for orthodontic reasons. Brackets were irradiated with 2 lasers. Laser No. 1 was an erbium-chromium (Er,Cr:YSGG) laser (Waterlase Express; Biolase, Irvine, USA) with a wavelength of 2,780 nm at a power of 2.78-2.85 W, energy of 185-190 mJ, fluence of 10 ns, frequency of 25 Hz, pulse duration of 300 μs, tip diameter of 0.6 mm, air/fluid cooling of 3.5 mL/s, and time of irradiation of 5-25 s. Laser No. 2 was an Er:YAG laser (LiteTouch; Light Instruments Ltd., Yokneam, Israel) with a wavelength of 2,940 nm at a power of 4 W, energy of 200 mJ, fluence of 10 ns, frequency of 20 Hz, pulse duration of 300 μs, tip diameter of 0.8 mm, air/fluid cooling of 3.5 mL/s, and time of irradiation of 5-15 s. Two thermographic cameras (FLIR Zenmuse XT and FLIR P65; FLIR Systems, Wilsonville, USA) and type K thermocouple (Zhangzhou Weihua Electronic Co., Fujian, China) were used for precise temperature measurement on the surface of the teeth and inside them.

RESULTS

When laser No. 1 was in use, the mean difference between the inner and outer temperature of the examined teeth (1.4°C) was higher than when the laser No. 2 was in use (0.6°C) (p = 0.0974). The study found that the temperature inside the tooth did not increase, and it even decreased during treatment with Er:YAG laser using water cooling, provided that appropriate proportion of water and air was used. For laser No. 1, confidence interval (CI) was between 0.7 and 2.2 and for laser No. 2 it was between 0.500 and 1.23. Only experiment for ceramic brackets was described.

CONCLUSIONS

These findings confirm that the use of Er:YAG family lasers for orthodontic bracket debonding in an in vitro study is safe and effective.

Development of a Novel Multi-Channel Thermocouple Array Sensor for In-Situ Monitoring of Ice Accretion

A test was performed to determine the efficacy of a novel multi-channel thermocouple temperature sensor employing "N+1" array architecture for the in-situ detection of icing in cold climates. T-type thermoelements were used to fabricate a sensor with six independent temperature sensing points, capable of two-dimensional temperature mapping. The sensor was intended to detect the high latent heat of fusion of water (334 J/g) which is released to the environment during ice formation. The sensor was embedded on a plywood board and an aluminium plate, respectively by an epoxy resin. Three different ice accretion cases were considered. Ice accretion for all cases was achieved on the surface of the resin layer. In order to analyse the temperature variation for all three cases, the first 20 s response for each case was averaged between three cases. A temperature increase of (1.0 ± 0.1) °C and (0.9 ± 0.1) °C was detected by the sensors 20 s after the onset of icing, attributed to the latent heat of fusion of water. The results indicate that the sensor design is well-suited to cold temperature applications and that detection of the latent heat of fusion could provide a rapid and robust means of icing detection.

The Gas Fire Temperature Measurement for Detection of an Object's Presence on Top of the Burner

This article covers the topic of temperature measurement on top of a gas burner fire in order to recognize pot removal from a gas burner and subsequently, to cut off the gas supply. The possibility of applying a factory-mounted thermocouple was investigated with the assumption that its output signal could be used to detect the presence of a pot on a gas burner. However, the characteristic of such a thermocouple is not fully linear and as the research has shown that such a thermocouple would not fit enough for the assumed purpose, thus another sensor needs to be used. Therefore, in this paper, the linear thermocouple and IR diode are used. The best localizations of theses sensors were investigated in order to obtain a signal suitable for the pot presence recognition over the burner. These investigations are supported by the use of an infrared camera. In the investigations, the temperature changes also caused by casual air blast or caused by increasing and decreasing the valve opening are recorded and analyzed. Finally, the changes of the thermocouple's signals are used as an input signal to propose an algorithm for pot absence recognition over the burner. The microprocessor-based circuit with a control unit for detection of the pot absence is designed, built and investigated.

Textile-Integrated Thermocouples for Temperature Measurement

The integration of conductive materials in textiles is key for detecting temperature in the wearer´s environment. When integrating sensors into textiles, properties such as their flexibility, handle, and stretch must stay unaffected by the functionalization. Conductive materials are difficult to integrate into textiles, since wires are stiff, and coatings show low adhesion. This work shows that various substrates such as cotton, cellulose, polymeric, carbon, and optical fiber-based textiles are used as support materials for temperature sensors. Suitable measurement principles for use in textiles are based on resistance changes, optical interferences (fiber Bragg grating), or thermoelectric effects. This review deals with developments in the construction of temperature sensors and the production of thermocouples for use in textiles. The operating principle of thermocouples is based on temperature gradients building up between a heated and a cold junction of two conductors, which is converted to a voltage output signal. This work also summarizes integration methods for thermocouples and other temperature-sensing techniques as well as the manufacture of conductive materials in textiles. In addition, textile thermocouples are emphasized as suitable and indispensable elements in sensor concepts for smart textiles.

Iterative Curve Fitting of the Bioheat Transfer Equation for Thermocouple-Based Temperature Estimation In Vitro and In Vivo

Temperature measurements with thin thermocouples embedded in ultrasound fields are strongly subjected to a viscous heating artifact (VHA). The artifact contribution decays over time; therefore, it can be minimized at late temperature readings. However, previous studies have failed to demonstrate a rigorous method for determining the optimal time point at which the artifact contribution is negligible. In this study, we present an iterative processing method based on successive curve fittings using an artifact-independent model. The fitting starting point moves at each iteration until the maximum R² indicates where the viscous heating is minimum. A solution of the bioheat transfer equation is used to account for blood perfusion, thus enabling in vivo measurements. Three T-type thermocouples with different diameters and sensitivities were assessed in an excised canine liver and in the mouse brain in vivo. We found that the artifact constitutes up to 81% ± 5% of wire thermocouple readings. The best-fit time varied in the liver samples ( n = 3 ) from 0 to 3.335 ± 0.979 s and in the mouse brain ( n = 5 ) from 0 to 0.498 ± 0.457 s at variable experimental conditions, which clearly demonstrates the need of the method for finding the appropriate starting time point of the fit. This study introduces a statistical method to determine the best time to fit a curve that can back-estimate temperature in tissues under ultrasound exposure using thermocouples. This method allows temperature evaluation in vivo and in vitro during a validation and safety assessment of a wide range of therapeutic and diagnostic ultrasound modalities.

Heat Generation Changes with Electrically Heated Pluggers after Multiple Autoclave Cycles at Different Operating Temperatures

INTRODUCTION

Electrically heated pluggers are the most commonly used instruments during warm obturation techniques. This study aimed to evaluate the effect of sterilization and operating temperature settings on the heat generation of pluggers of various taper sizes.

METHODS

Fifty pluggers were sterilized at 132°C for 25 minutes for a total of 150 cycles. One group (Autoclave200) consisted of 25 pluggers tested at an operating temperature setting of 200°C, whereas another group (Autoclave400) consisted of 25 pluggers tested at 400°C. The heat generation at their tip surface was measured with T-type thermocouples at 0, 50, 100, and 150 autoclave cycles. An unpaired t test was used to compare the time it took the pluggers to reach 60°C and the mean maximum temperature change.

RESULTS

After 50 autoclave cycles, all of the 0.04 taper pluggers in Autoclave200 failed to reach 60°C. After 100 autoclave cycles, one of the 0.10 taper pluggers in Autoclave200 did not reach 60°C, and after 150 autoclave cycles, one of the 0.04 taper pluggers failed to generate any heat. The mean increase in the time to reach 60°C ranged from 1071-4004 milliseconds and 510-2074 milliseconds for Autoclave200 and Autoclave400, respectively. The mean maximum temperature change decreased by 13-29°C and 24-116°C for Autoclave200 and Autoclave400, respectively.

CONCLUSIONS

After multiple autoclave cycles and higher operating temperature use, the electrically heated pluggers transferred less heat to the tip surface, potentially making them less effective.

Specimen Temperature Detection on a Clinical Laboratory Pre-Analytic Automation Track: Implications for Direct-from-Track Total Laboratory Automation (TLA) Systems

Clinical laboratory regulations require temperature monitoring of facilities, reagent and specimen storage, as well as temperature-dependent equipment. Real-time specimen temperature detection has not yet been integrated into total laboratory automation (TLA) solutions. An infrared (IR) pyrometer was paired with a complementary metal oxide semiconductor (CMOS) laser sensor and connected to an embedded networked personal computer (PC) to create a modular temperature detection unit for closed, moving clinical laboratory specimens. Accuracy of the detector was assessed by comparing temperature measurements to those obtained from thermocouples connected to battery-operated data loggers. The temperature detector was then installed on a pre-analytic laboratory automation system to assess specimen temperature before and after processing on an integrated thawing and mixing (T/M) robotic workcell. The IR temperature detector was able to accurately record temperature of closed, moving specimens on a pre-analytic automation system. The effectiveness of the T/M workcell was independently verified using the temperature detector. Specimen reroute on the pre-analytic automation track was identified as a potential risk for frozen specimens being inadvertently delivered to future, connected instrumentation. Automated IR temperature detection can be used to verify specimen temperature prior to instrument loading and/or sampling. Such systems could be used to prevent frozen specimens from being inadvertently loaded onto analytical instrumentation in TLA solutions.

Fabrication and Characterization of Flexible Thermoelectric Generators Using Micromachining and Electroplating Techniques

This study involves the fabrication and measurement of a flexible thermoelectric generator (FTG) using micromachining and electroplating processes. The area of the FTG is 46 × 17 mm², and it is composed of 39 thermocouples in series. The thermoelectric materials that are used for the FTG are copper and nickel. The fabrication process involves patterning a silver seed layer on the polymethyl methacrylate (PMMA) substrate using a computer numerical control (CNC) micro-milling machine. Thermoelectric materials, copper and nickel, are deposited on the PMMA substrate using an electroplating process. An epoxy polymer is then coated onto the PMMA substrate. Acetone solution is then used to etch the PMMA substrate and to transfer the thermocouples to the flexible epoxy film. The FTG generates an output voltage (OV) as the thermocouples have a temperature difference (ΔT) between the cold and hot parts. The experiments show that the OV of the FTG is 4.2 mV at ΔT of 5.3 K and the output power is 429 nW at ΔT of 5.3 K. The FTG has a voltage factor of 1 μV/mm²K and a power factor of 19.5 pW/mm²K². The FTG reaches a curvature of 20 m^-1.

Kinesio® Tape Barrier Does Not Inhibit Intramuscular Cooling During Cryotherapy

CONTEXT

Allied health care professionals commonly apply cryotherapy as treatment for acute musculoskeletal trauma and the associated symptoms. Understanding the impact of a tape barrier on intramuscular temperature can assist in determining treatment duration for effective cryotherapy.

OBJECTIVE

To determine whether Kinesio® Tape acts as a barrier that affects intramuscular temperature during cryotherapy application.

DESIGN

A repeated-measures, counterbalanced design in which the independent variable was tape application and the dependent variable was muscle temperature as measured by thermocouples placed 1 cm beneath the adipose layer. Additional covariates for robustness were body mass index and adipose thickness.

SETTING

University research laboratory.

PARTICIPANTS

Nineteen male college students with no contraindications to cryotherapy, no known sensitivity to Kinesio® Tape, and no reported quadriceps injury within the past 6 months.

INTERVENTION

Topical cryotherapy: cubed ice bags of 1 kg and 0.5 kg.

MAIN OUTCOME MEASURES

Intramuscular temperature.

RESULTS

The tape barrier had no statistically significant effect on muscle temperature. The pattern of temperature change was indistinguishable between participants with and without tape application.

CONCLUSIONS

Findings suggest that health care professionals can combine cryotherapy with a Kinesio® Tape application without any need for adjustments to cryotherapy duration.

Multifunctional Freestanding Microprobes for Potential Biological Applications

Deep-level sensors for detecting the local temperatures of inner organs and tissues of an animal are rarely reported. In this paper, we present a method to fabricate multifunctional micro-probes with standard cleanroom procedures, using a piece of stainless-steel foil as the substrate. On each of the as-fabricated micro-probes, arrays of thermocouples made of Pd-Cr thin-film stripes with reliable thermal sensing functions were built, together with Pd electrode openings for detecting electrical signals. The as-fabricated sword-shaped freestanding microprobes with length up to 30 mm showed excellent mechanical strength and elastic properties when they were inserted into the brain and muscle tissues of live rats, as well as suitable electrochemical properties and, therefore, are promising for potential biological applications.

The effect of varying degrees of compression from elastic vs plastic wrap on quadriceps intramuscular temperature during wetted ice application

The aim of this study was to evaluate and compare the effectiveness of wetted ice bag, applied with high compression elastic wrap or held in place with low compression plastic wrap, on reducing vastus lateralis intramuscular temperature and skin surface temperature. Ten healthy male participants had wetted ice packs applied to a standardized area on the anterior aspect of the quadriceps simultaneously to both legs for 30 minutes. The ice pack was secured with high compression (elastic wrap) to the left anterior thigh (60.6 ± 8.1 mm Hg) and low compression (plastic wrap) to the right anterior thigh (15.5 ± 4.0 mm Hg). Intramuscular temperature (1 and 3 cm) and skin temperature of the vastus lateralis were measured continuously during a 10-minute baseline period, 30-minute treatment period, and a 60-minute recovery period. No difference was observed between treatments in terms of the magnitude of reduction in intramuscular temperature at both 1 and 3 cm and skin temperature regardless of compression pressure (P > 0.05). Temperature upon conclusion of elastic wrap treatment was as follows: 17.8 ± 5.2°C at 1 cm and 23.1 ± 4.9°C at 3 cm; plastic wrap treatment: 17.9 ± 4.4°C at 1 cm and 24.5 ± 6.7°C at 3 cm. Plastic wraps may offer a practical alternative to elastic wraps for clinicians as they may be disposed of by the patient or athlete without having to stay at the treatment facility.

A Through-Hole Lead Connection Method for Thin-Film Thermocouples on Turbine Blades

To solve the current problems with thin-film thermocouple signals on turbine blades in ultra-high temperature environments, this study explores the use of a through-hole lead connection technology for high-temperature resistant nickel alloys. The technique includes through-hole processing, insulation layer preparation, and filling and fixing of a high-temperature resistant conductive paste. The through-hole lead connection preparation process was optimized by investigating the influence of the inner diameter of the through-hole, solder volume, and temperature treatment on the contact strength and surface roughness of the thin-film for contact resistance. Finally, the technology was combined with a thin-film thermocouple to perform multiple thermal cycling experiments on the surface of the turbine blade at a temperature of 1000 °C. The results show that the through-hole lead connection technology can achieve a stable output of the thin-film thermocouple signal on the turbine blade.

Screen-Printed, Pure Carbon-Black Thermocouple Fabrication and Seebeck Coefficients

Thermocouples classically consist of two metals or semiconductor components that are joined at one end, where temperature is measured. Carbon black is a low-cost semiconductor with a Seebeck coefficient that depends on the structure of the carbon particles. Different carbon black screen-printing inks generally exhibit different Seebeck coefficients, and two can therefore be combined to realize a thermocouple. In this work, we used a set of four different commercially available carbon-black screen-printing inks to print all-carbon-black thermocouples. The outputs of these thermocouples were characterized and their Seebeck coefficients determined. We found that the outputs of pure carbon-black thermocouples are reasonably stable, linear, and quantitatively comparable to those of commercially available R- or S-type thermocouples. It is thus possible to fabricate thermocouples by an easily scalable, cost-efficient process that combines two low-cost materials.

Fabrication and Thermoelectric Characterization of Transition Metal Silicide-Based Composite Thermocouples

Metal silicide-based thermocouples were fabricated by screen printing thick films of the powder compositions onto alumina tapes followed by lamination and sintering processes. The legs of the embedded thermocouples were composed of composite compositions consisting of MoSi₂, WSi₂, ZrSi₂, or TaSi₂ with an additional 10 vol % Al₂O₃ to form a silicide⁻oxide composite. The structural and high-temperature thermoelectric properties of the composite thermocouples were examined using X-ray diffraction, scanning electron microscopy and a typical hot⁻cold junction measurement technique. MoSi₂-Al₂O₃ and WSi₂-Al₂O₃ composites exhibited higher intrinsic Seebeck coefficients (22.2⁻30.0 µV/K) at high-temperature gradients, which were calculated from the thermoelectric data of composite//Pt thermocouples. The composite thermocouples generated a thermoelectric voltage up to 16.0 mV at high-temperature gradients. The MoSi₂-Al₂O₃//TaSi₂-Al₂O₃ thermocouple displayed a better performance at high temperatures. The Seebeck coefficients of composite thermocouples were found to range between 20.9 and 73.0 µV/K at a temperature gradient of 1000 °C. There was a significant difference between the calculated and measured Seebeck coefficients of these thermocouples, which indicated the significant influence of secondary silicide phases (e.g., Mo₅Si₃, Ta₅Si₃) and possible local compositional changes on the overall thermoelectric response. The thermoelectric performance, high sensitivity, and cost efficiency of metal silicide⁻alumina ceramic composite thermocouples showed promise for high-temperature and harsh-environment sensing applications.

Effect of Temperature Distribution in Ultrasonically Welded Joints of Copper Wire and Sheet Used for Electrical Contacts

The temperature distribution occurring at the interface while joining a simple electrical contact comprising of a copper wire and a copper sheet using ultrasonic metal welding was analyzed using finite element method. Heat flux due to plastic deformation and friction was calculated and provided as input load for simulation of temperature distribution. The results of temperature obtained from simulation are found to be in good agreement with the results of temperature from experiments measured using thermocouple. Special focus was given to how the heat generated at the wire⁻sheet interface affect the strength of the joint in tension. With the knowledge of heat generated at the interface while welding, it is possible to control the strength of the joint and produce defect free joints. Based on the results from finite element analysis and experiments, it is observed that the influence of heat developed due to friction and plastic deformation of metallic specimens has a significant effect on the progress of welding and strength of the joint.

Seebeck Coefficient of Thermocouples from Nickel-Coated Carbon Fibers: Theory and Experiment

Thermocouples made of etched and non-etched nickel-coated carbon yarn (NiCCY) were investigated. Theoretic Seebeck coefficients were compared to experimental results from measurements of generated electric voltage by these thermocouples. The etching process for making thermocouples was performed by immersion of NiCCY in the solution containing a mixture of hydrochloric acid (HCl) (37% of concentration), and hydrogen peroxide (H₂O₂) in three different concentrations-3%, 6%, and 10%. Thirty minutes of etching to remove Ni from NiCCY was followed by washing and drying. Next, the ability to generate electrical voltage by the thermocouples (being a junction of the etched and the non-etched NiCCY) was measured in different ranges of temperatures, both a cold junction (291.15⁻293.15 K) and a hot junction (293.15⁻325.15 K). A formula predicting the Seebeck coefficient of this thermocouple was elaborated, taking into consideration resistance values of the tested samples. It was proven that there is a good agreement between the theoretical and experimental data, especially for the yarns etched with 6% and 10% peroxide (both were mixed with HCl). The electrical resistance of non-fully etched nickel remaining on the carbon fiber surface ( R 1 ) can have a significant effect on the thermocouples' characteristics.

A Highly Thermostable In₂O₃/ITO Thin Film Thermocouple Prepared via Screen Printing for High Temperature Measurements

An In₂O₃/ITO thin film thermocouple was prepared via screen printing. Glass additives were added to improve the sintering process and to increase the density of the In₂O₃/ITO films. The surface and cross-sectional images indicate that both the grain size and densification of the ITO and In₂O₃ films increased with the increase in annealing time. The thermoelectric voltage of the In₂O₃/ITO thermocouple was 53.5 mV at 1270 °C at the hot junction. The average Seebeck coefficient of the thermocouple was calculated as 44.5 μV/°C. The drift rate of the In₂O₃/ITO thermocouple was 5.44 °C/h at a measuring time of 10 h at 1270 °C.

Histological and Thermometric Examination of Soft Tissue De-Epithelialization Using Digitally Controlled Er:YAG Laser Handpiece: An Ex Vivo Study

OBJECTIVE

The purpose of this study was histological and thermometric examination of soft tissue de-epithelialization using digitally controlled laser handpiece (DCLH) - X-Runner.

BACKGROUND DATA

Commonly used techniques for de-epithelialization include scalpel, abrasion with diamond bur, or a combination of the two. Despite being simple, inexpensive and effective, these techniques are invasive and may produce unwanted side effects. It is important to look for alternative techniques using novel tools, which are minimally invasive and effective.

MATERIALS AND METHODS

114 porcine samples sized 6 × 6 mm were collected from the attached gingiva (AG) of the alveolar process of the mandible using 15C scalpel blade. The samples were irradiated by means of Er:YAG laser (LightWalker, Fotona, Slovenia), using X-Runner and HO₂ handpieces at different parameters; 80, 100, and 140 mJ/20 Hz in time of 6 or 16 sec, respectively. The temperature was measured with a K-type thermocouple. For the histopathological analysis of efficiency of epithelium removal and thermal injury, 3 random samples were de-epithelialized with an HO₂ handpiece, and 9 random samples with an X-Runner handpiece with different parameters. For the samples irradiated with DCLH, we have used three different settings, which resulted in removing 1 to 3 layers of the soft tissue. The efficiency of epithelium removal and the rise of temperature were analyzed.

RESULTS

DCLH has induced significantly lower temperature increase compared with HO₂ at each energy to frequency ratio. The histological examination revealed total epithelium removal when HO₂ handpiece was used at 100 and 140 mJ/20 Hz and when DCLH was used for two- and threefold lasing at 80, 100, and 140 mJ/20 Hz.

CONCLUSIONS

Er:YAG laser with DCLH handpiece may be an efficient tool in epithelium removal without excessive thermal damage.

Improved Dental Implant Drill Durability and Performance Using Heat and Wear Resistant Protective Coatings

The dental implant drilling procedure is an essential step for implant surgery, and frictional heat in bone during drilling is a key factor affecting the success of an implant. The aim of this study was to increase the dental implant drill lifetime and performance by using heat- and wear-resistant protective coatings to decrease the alveolar bone temperature caused by the dental implant drilling procedure. Commercially obtained stainless steel drills were coated with titanium aluminum nitride, diamond-like carbon, titanium boron nitride, and boron nitride coatings via magnetron-sputter deposition. Drilling was performed on bovine femoral cortical bone under the conditions mimicking clinical practice. Tests were performed under water-assisted cooling and under the conditions when no cooling was applied. Coated drill performances and durabilities were compared with those of three commonly used commercial drills with surfaces made from zirconia, black diamond. and stainless steel. Protective coatings with boron nitride, titanium boron nitride, and diamond-like carbon have significantly improved drill performance and durability. In particular, boron nitride-coated drills have performed within safe bone temperature limits for 50 drillings even when no cooling is applied. Titanium aluminium nitride coated drills did not show any improvement over commercially obtained stainless steel drills. Surface modification using heat- and wear-resistant coatings is an easy and highly effective way to improve implant drill performance and durability, which can improve the surgical procedure and the postsurgical healing period. The noteworthy success of different types of coatings is novel and likely to be applicable to various other medical systems.

Thermoelectric Mixed Thick-/Thin Film Microgenerators Based on Constantan/Silver

This paper describes the design, manufacturing and characterization of newly developed mixed thick-/thin film thermoelectric microgenerators based on magnetron sputtered constantan (copper-nickel alloy) and screen-printed silver layers. The thermoelectric microgenerator consists of sixteen thermocouples made on a 34.2 × 27.5 × 0.25 mm³ alumina substrate. One of thermocouple arms was made of magnetron-sputtered constantan (Cu-Ni alloy), the second was a Ag-based screen-printed film. The length of each thermocouple arm was equal to 27 mm, and their width 0.3 mm. The distance between the arms was equal to 0.3 mm. In the first step, a pattern mask with thermocouples was designed and fabricated. Then, a constantan layer was magnetron sputtered over the whole substrate, and a photolithography process was used to prepare the first thermocouple arms. The second arms were screen-printed onto the substrate using a low-temperature silver paste (Heraeus C8829A or ElectroScience Laboratories ESL 599-E). To avoid oxidation of constantan, they were fired in a belt furnace in a nitrogen atmosphere at 550/450 °C peak firing temperature. Thermoelectric and electrical measurements were performed using the self-made measuring system. Two pyrometers included into the system were used for temperature measurement of hot and cold junctions. The estimated Seebeck coefficient, α was from the range 35 − 41 µV/K, whereas the total internal resistances R were between 250 and 3200 ohms, depending on magnetron sputtering time and kind of silver ink (the resistance of a single thermocouple was between 15.5 and 200 ohms).

Comparison of temperature change among different adhesive resin cement during polymerization process

Purpose:

The aim of this study was to assess the intra-pulpal temperature changes in adhesive resin cements during polymerization.

Materials and Methods:

Dentin surface was prepared with extracted human mandibular third molars. Adhesive resin cements (Panavia F 2.0, Panavia SA, and RelyX U200) were applied to the dentin surface and polymerized under IPS e.max Press restoration. K-type thermocouple wire was positioned in the pulpal chamber to measure temperature change (n = 7). The temperature data were recorded (0.0001 sensible) and stored on a computer every 0.1 second for sixteen minutes. Differences between the baseline temperature and temperatures of various time points (2, 4, 6, 8, 10, 12, 14, and 16 minute) were determined and mean temperature changes were calculated. At various time intervals, the differences in temperature values among the adhesive resin cements were analyzed by two-way ANOVA and post-hoc Tukey honestly test (α = 0.05).

Results:

Significant differences were found among the time points and resin cements (P < 0.05). Temperature values of the Pan SA group were significantly higher than Pan F and RelyX (P < 0.05).

Conclusion:

Result of the study on self-adhesive and self-etch adhesive resin cements exhibited a safety intra-pulpal temperature change.

Microscale temperature and SAR measurements in cell monolayer models exposed to millimeter waves

Due to shallow penetration of millimeter waves (MMW) and convection in liquid medium surrounding cells, the problem of accurate assessment of local MMW heating in in vitro experiments remains unsolved. Conventional dosimetric MMW techniques, such as infrared imaging or fiber optic (FO) sensors, face several inherent limits. Here we propose a methodology for accurate local temperature measurement and subsequent specific absorption rate (SAR) retrieval using microscale thermocouples (TC). SAR was retrieved by fitting the measured initial temperature rise to the numerical solution of an equivalent thermal model. It was found that the accuracy of temperature measurement depends on thermosensor size, that is, the smaller TC, the more accurate the temperature measurement. SAR determined using TC with lead diameters of 25 and 75 μm demonstrated 98.5% and 80.4% match with computed SAR, respectively. However, both TC provided the same temperature rises in long run (> 10 min). FO probe failed to measure adequately local heating both for short and long exposures due to the relatively large size of the probe sensor (400 μm) and time constant (0.6 s). Calculated SAR in the cell monolayer was almost two times lower than that in the surrounding liquid. It was shown that the impact of the cell monolayer on heating due to its small thickness (5 to 10 μm) can be considered as negligible. Moreover, we demonstrated the possibility of accurate measurement of MMW-induced thermal pulses (up to 10 °C) using 25 μm TC. Bioelectromagnetics. 38:11-21, 2017. © 2016 Wiley Periodicals, Inc.

Exploring thermal anisotropy of cortical bone using temperature measurements in drilling

BACKGROUND

Bone drilling is widely used in orthopaedics for fracture treatment, reconstructive surgery and bone biopsy. Heat generation in bone drilling can cause rise in bone temperature resulting in prolonged healing time or loosening of fixation.

OBJECTIVE

The purpose of this study was to investigate thermal anisotropy of bone by measuring the level of temperature in bone drilling with and without cooling conditions in two anatomical directions.

METHODS

Drilling tests were performed on bovine cortical bone. A total of fifteen specimens were used to obtain data for statistical analysis. Temperature near the cutting zone was measured in two anatomical directions. i.e. along the longitudinal and circumferential direction. Temperature distribution was also found in the two prescribed directions. Analysis of variance (ANOVA) was used to identify significant drilling parameter affecting bone temperature.

RESULTS

Drilling speed, feed rate and drill size were found influential parameters affecting bone temperature. Higher drilling speed, feed rate, and large drill size were found to cause elevated temperature in bone. Much lower temperature was measured in bone when cooling fluid was supplied to the drilling region. Experimental results revealed lower temperatures in the circumferential direction compared to the longitudinal direction.

CONCLUSIONS

Thermal anisotropy for heat transport was found in the bone. This study recommends lower drilling speed and feed rate and cooling for controlling rise in bone temperature.

Temperature Changes in Cortical Bone after Implant Site Preparation Using a Single Bur versus Multiple Drilling Steps: An In Vitro Investigation

OBJECTIVES

The study aims to test the hypothesis of no differences in temperature variation by using a single bur for implant site preparation as compared with conventional drilling sequence using multiple burs with incremental diameter.

MATERIALS AND METHODS

Synthetic blocks of bone (type I density) were used for drilling procedures.

THREE GROUPS WERE EVALUATED

Group 1 and Group 2 - drilling with three consecutive burs for a 4.1 mm cylindrical implant and for a 4.3 mm conical implant, respectively; Group 3 - drilling with a single bur for a 4.2 mm conical implant. For each group, 20 drilling procedures were performed without irrigation and 20 with external irrigation. The temperature in the cortical bone during osteotomy for implant site preparation was measured through a thermocouple.

RESULTS

The mean temperatures and standard deviations for the drilling without irrigation were: 25.5 ± 1.24°C for Group 1; 28.1 ± 1.76°C for Group 2; 26.5 ± 1.79°C for Group 3. Considering the drilling with irrigation, the mean values and standard deviations were: 20.4 ± 1.17°C for Group 1; 22.2 ± 1.38°C for Group 2; 20.2 ± 0.83°C for Group 3. Groups 1 and 3 yielded similar results, while Group 2 displayed significantly higher temperature increase than the other two groups.

CONCLUSIONS

The single bur drilling protocol did not produce greater bone heating than the conventional protocol and may be considered a safe procedure.

Microhotplate Temperature Sensor Calibration and BIST

In this paper we describe a novel long-term microhotplate temperature sensor calibration technique suitable for Built-In Self Test (BIST). The microhotplate thermal resistance (thermal efficiency) and the thermal voltage from an integrated platinum-rhodium thermocouple were calibrated against a freshly calibrated four-wire polysilicon microhotplate-heater temperature sensor (heater) that is not stable over long periods of time when exposed to higher temperatures. To stress the microhotplate, its temperature was raised to around 400 °C and held there for days. The heater was then recalibrated as a temperature sensor, and microhotplate temperature measurements were made based on the fresh calibration of the heater, the first calibration of the heater, the microhotplate thermal resistance, and the thermocouple voltage. This procedure was repeated 10 times over a period of 80 days. The results show that the heater calibration drifted substantially during the period of the test while the microhotplate thermal resistance and the thermocouple-voltage remained stable to within about plus or minus 1 °C over the same period. Therefore, the combination of a microhotplate heater-temperature sensor and either the microhotplate thermal resistance or an integrated thin film platinum-rhodium thermocouple can be used to provide a stable, calibrated, microhotplate-temperature sensor, and the combination of the three sensor is suitable for implementing BIST functionality. Alternatively, if a stable microhotplate-heater temperature sensor is available, such as a properly annealed platinum heater-temperature sensor, then the thermal resistance of the microhotplate and the electrical resistance of the platinum heater will be sufficient to implement BIST. It is also shown that aluminum- and polysilicon-based temperature sensors, which are not stable enough for measuring high microhotplate temperatures (>220 °C) without impractically frequent recalibration, can be used to measure the silicon substrate temperature if never exposed to temperatures above about 220 °C.

Focusing of high-intensity ultrasound through the rib cage using a therapeutic random phased array

A method for focusing high-intensity ultrasound (HIFU) through a rib cage that aims to minimize heating of the ribs while maintaining high intensities at the focus (or foci) was proposed and tested theoretically and experimentally. Two approaches, one based on geometric acoustics and the other accounting for diffraction effects associated with propagation through the rib cage, were investigated theoretically for idealized source conditions. It is shown that for an idealized radiator, the diffraction approach provides a 23% gain in peak intensity and results in significantly less power losses on the ribs (1% vs. 7.5% of the irradiated power) compared with the geometric one. A 2-D 1-MHz phased array with 254 randomly distributed elements, tissue-mimicking phantoms and samples of porcine rib cages are used in experiments; the geometric approach is used to configure how the array is driven. Intensity distributions are measured in the plane of the ribs and in the focal plane using an infrared camera. Theoretical and experimental results show that it is possible to provide adequate focusing through the ribs without overheating them for a single focus and several foci, including steering at +/- 10-15 mm off and +/- 20 mm along the array axis. Focus splitting caused by the periodic spatial structure of ribs is demonstrated both in simulations and experiments; the parameters of splitting are quantified. The ability to produce thermal lesions with a split focal pattern in ex vivo porcine tissue placed beyond the rib phantom is also demonstrated. The results suggest that the method is potentially useful for clinical applications of HIFU, for which the rib cage lies between the transducer(s) and the targeted tissue.

Local ice-bag application and triceps surae muscle temperature during treadmill walking

CONTEXT

Ice bags "to go" are a common practice in athletic training.

OBJECTIVE

To determine the effect of submaximal exercise on tissue temperatures during a common ice-bag application.

DESIGN

2 X 5 fully repeated-measures design with treatment (cooling while resting, cooling while walking) and time (pretreatment, immediately after ice application, and at 10, 20, and 30 minutes during treatment) as the independent variables.

SETTING

Laboratory setting.

PATIENTS OR OTHER PARTICIPANTS

Sixteen healthy, physically active volunteers (age = 21.63 +/- 2.63 yrs, height = 68.97 +/- 4.00 cm, mass = 80.97 +/- 18.18 kg, calf skinfold = 21.1 +/- 9.3 mm).

MAIN OUTCOME MEASURE(S)

Left triceps surae intramuscular and skin temperatures, as measured by thermocouples to the nearest 0.1 degrees C, served as dependent measures.

INTERVENTION(S)

After collecting baseline temperatures, we secured a 1.0-kg ice bag to the calf using plastic wrap before the subject either rested prone or walked on a treadmill at 4.5 km/h for 30 minutes.

RESULTS

Treatment did not (P < 0.10) affect the approximately 15 degrees C (P < 0.0001) surface temperature decrease, which remained depressed immediately upon ice-bag application (P < 0.05). Conversely, intramuscular temperature continually cooled (34 to 28 degrees C), while subjects rested (P < 0.0001), whereas no change took place during walking (P = 0.49). Moreover, at the 20- and 30-minute treatment intervals, the resting intramuscular temperatures were, respectively, 3.9 degrees C and 5.4 degrees C cooler than the walking intramuscular temperatures (P < 0.01).

CONCLUSIONS

The current trend of wrapping "to go" ice bags to the leg is not likely to achieve deep tissue cooling despite surface temperature decreases.

Cold Modalities With Different Thermodynamic Properties Produce Different Surface and Intramuscular Temperatures

OBJECTIVE: To compare surface cooling and deep cooling produced by 3 common forms of cryotherapy. DESIGN AND SETTING: We used a 3 x 4 x 4 factorial with repeated measures on measurement depth and treatment. Independent variables were measurement depth (surface, fat + 1 cm, and fat + 2 cm), treatment (ice bag, Wet-Ice, Flex-i-Cold, and control), and treatment order (first, second, third, and fourth). The lowest temperature recorded was the dependent variable. The treatment order was counterbalanced using a Latin square. Data were analyzed with a repeated-measures analysis of variance. SUBJECTS: Fifteen collegiate volunteers who were free of lower extremity abnormalities. MEASUREMENTS: Thigh skin and thigh intramuscular temperatures (1- and 2-cm subadipose) were measured at 30-second intervals both before and during the 30-minute treatments using fine-wire implantable and surface thermocouples. The coldest recorded temperatures were analyzed. RESULTS: Statistical differences were observed for the depth-by-treatment interaction as well as for the depth and treatment main effects. During cold treatments, superficial depths were colder than deeper depths, and all cold treatments were colder than controls at all depths. For the interaction effect at both the skin surface and at 1-cm subadipose, the ice-bag and Wet-Ice treatments were colder than the Flex-i-Cold treatment. For the interaction at 2-cm subadipose, the cold treatments did not differ from each other. Order of treatments did not produce a significant effect. CONCLUSIONS: During a 30-minute cryotherapy treatment, modalities that undergo a phase change caused lower skin and 1-cm intramuscular temperatures than cold modalities that do not possess these properties. These differences were not seen at 2-cm subadipose but may become apparent with longer treatments.