Precise Thermal Control Research Articles

Study on PID temperature control performance of a novel PTC material with room temperature Curie point

Positive temperature coefficient (PTC) material is a kind of thermo-sensitive material, using PTC resistors to replace the ordinary resistive materials as heating elements may become a new means of precise temperature control for electronic devices. In this paper, a novel PTC material with Curie temperature of 34°C was prepared and the new thermal control method of combining PTC material with Proportional-Integral-Derivative (PID) control algorithm was proposed. The experimental system and mathematical model of PID temperature control by using PTC material were established. Based on this, the PID temperature control performance of PTC material was investigated with a comparison of ordinary resistance heater experimentally and theoretically. The results show that using PTC material for PID temperature control can effectively reduce overshoot; while the parameters of PID controller are within certain ranges, temperature control effects of PTC material are superior to ordinary heater, the temperature overshoot is reduced and the temperature control accuracy is increased. Furthermore, preparing PTC material with larger resistance-temperature coefficient may likely contribute to improve its PID temperature control effect. The research results specify possible directions for PID temperature control by using PTC materials in order to achieve precise thermal control of electronic devices.

Development of Near-Field-Enhanced High-Fill-Factor MEMS Radiator with Shared Spring

For precise thermal control in satellites under varying internal heat dissipation and thermal boundary condition, we propose a high-fill factor MEMS radiator enhanced by the near-field effect. We have successfully fabricated a prototype with parylene shared springs and achieved a fill factor of as high as 89%. It is found that at the ON state, the diaphragm temperature is increased from 58.0 °C to 106.4 °C, showing 144% enhancement in the radiation heat flux.

(Invited) Novel Strategies for the Bottom-up Assembly of Nanowires into Highly Efficient Bulk Thermoelectrics

The predicted exponential increase in the United States’ energy demand over the foreseeable future could be met by supplementing existing sources of energy with new renewable and/or non-renewable energy sources. Alternately, increasing the energy efficiencies of the existing processes and systems through waste heat scavenging could be employed to offset, at least partially, the projected increase in the energy demand. The importance of this alternate scenario could be easily inferred from the data supplied by the Energy Information Administration (EIA), which indicates that 56-57% of all energy produced each year in the US is rejected as waste heat. In the case of automobiles the importance of waste heat recovery becomes more apparent, where approximately 70% of energy generated by burning gasoline is lost either in the engine coolant or through the exhaust. Use of solid-state thermoelectric modules is a minimally invasive method for scavenging waste heat from systems and processes. The lack of any moving parts, portability, very long operational lifetimes, and minimal maintenance make thermoelectrics attractive for waste heat recovery. The lack of the requisite materials for achieving a good $/watt heat-to-electricity conversion metric is currently preventing the large-scale deployment and use of thermoelectrics in terrestrial applications, and limits their use to niche applications (powering up deep space probes). A factor responsible for this bottleneck is the low efficiencies of the current thermoelectric materials, which in turn could be attributed to the lack of a pathway for precisely and independently tuning the thermal and electrical transport through them. Recent theoretical and experimental studies have demonstrated that nanostructuring of materials serves as a route for independently tuning the thermal and electrical transport. Most of these demonstrations were made using the following types of devices: suspended individual nanowire devices, thin-film superlattice devices, and bulk devices that have endotaxial nanostructures embedded within a host material. From these studies it could be concluded that although it appears that nanostructuring of materials for selectively reducing their thermal conductivities is the only essential requirement for enhancing their heat-to-electricity conversion efficiencies, the existence of an epitaxial relationship between the nanostructures after their assembly is also equally important for efficiency enhancement. Experimental methods employed for obtaining epitaxially-oriented bulk nanostructure assemblies require either the use of tedious process (e.g., atomic layer deposition, ALD) or the use of a specific scientific phenomenon (e.g., spinodal decomposition). These requirements not only make it impossible to mass produce thermoelectrics (ALD is a slow and non-scalable process), but also limit the applicability of these strategies to a few material systems (spinodal decomposition is currently only observed in a few materials systems composed of Pb, Bi, Sb, Te and Sr). Finally, the progress made in experimentally demonstrating enhanced thermoelectric performances of large-scale nanowire assemblies is minimal at best. In this context, the aim of our work is the rational design and fabrication of next-generation, highly-efficient thermoelectrics through the development of strategies for mass producing nanowires and assembling them in an interface-engineered manner (1-3). The aim of this presentation is to showcase the progress that has been made in this research area by our group. The strategies useful for the mass production of nanowires and their in-situ functionalization with organic molecules (1), together with the strategies useful for assembling them in an interface-engineered manner on a large-scale into functional thermoelectric devices (2,3), will be presented. Demonstrations of how these strategies afford precise thermal and electrical transport control in bulk nanowire assemblies will be made using interface-engineered Zn3P2 and ZnO nanowire assemblies as illustrative examples (2-4). In addition, strategies for welding nanowires during assembly so as to ensure that the welds between the nanowires have the same chemical composition as those of the nanowires and that the nanowires assemblies have a single-crystalline path for electrical conduction will also be presented (5,6). Illustration of this concept will be made by demonstrating enhanced thermoelectric performance in Mg2Si nanowire assemblies obtained by welding pre-synthesized Si nanowires (6). ACKNOWLEDGEMENTS Partial financial support from NSF/DOE thermoelectrics Partnership (NSF CBET # 1048702) is gratefully acknowledged. REFERENCES L. Brockway, M. Van Laer, Y. Kang, S. Vaddiraju, Physical Chemistry Chemical Physics, 15, 6260-6267, (2013).L. Brockway, V. Vasiraju, S. Vaddiraju, Nanotechnology, 25, 125402 (2014).L. Brockway, V. Vasiraju, H. Asayesh-Ardakani, R. Shahbazian-Yassar, S. Vaddiraju, Nanotechnology, 25, 145401 (2014).L. Brockway, V. Vasiraju, M. K. Sunkara, S. Vaddiraju, ACS Applied Materials & Interfaces 6, 14923-14930 (2014).Y. Kang, L. Brockway, S. Vaddiraju, Materials Letters, 100, 106-110 (2013).Y. Kang, S. Vaddiraju, Chemistry of Materials, 26, 2814-2819 (2014).

C113 共有ばねを用いた高開口率MEMSラジエータに関する研究(OS-06:ふく射輸送制御(1))

For precise thermal control in satellites under varying internal heat dissipation and thermal boundary condition, we propose a high-fill factor MEMS radiator enhanced by near-field effect. In the present design, polymer springs are shared among adjacent diaphragms, and its structural parameters are decided based on analyses of its resonance frequency, driving voltage, and heat flux ratio. We have successfully fabricated our prototype and its fill factor is significantly improved as high as 89 %. The surface temperature on the diaphragm is measured with infrared thermal imager, and is increased from 67.4 ℃ to 77.9 ℃.

Development and field testing of a rapid and ultra-stable atmospheric carbon dioxide spectrometer

Abstract. We present field test results for a new spectroscopic instrument to measure atmospheric carbon dioxide (CO2) with high precision (0.02 μmol mol−1, or ppm at 1 Hz) and demonstrate high stability (within 0.1 ppm over more than 8 months), without the need for hourly, daily, or even monthly calibration against high-pressure gas cylinders. The technical novelty of this instrument (ABsolute Carbon dioxide, ABC) is the spectral null method using an internal quartz reference cell with known CO2 column density. Compared to a previously described prototype, the field instrument has better stability and benefits from more precise thermal control of the optics and more accurate pressure measurements in the sample cell (at the mTorr level). The instrument has been deployed at a long-term ecological research site (the Harvard Forest, USA), where it has measured for 8 months without on-site calibration and with minimal maintenance, showing drift bounds of less than 0.1 ppm. Field measurements agree well with those of a commercially available cavity ring-down CO2 instrument (Picarro G2301) run with a standard calibration protocol. This field test demonstrates that ABC is capable of performing high-accuracy, unattended, continuous field measurements with minimal use of reference gas cylinders.

Development of an Integrated Microfluidic Perfusion Cell Culture System for Real-Time Microscopic Observation of Biological Cells

This study reports an integrated microfluidic perfusion cell culture system consisting of a microfluidic cell culture chip, and an indium tin oxide (ITO) glass-based microheater chip for micro-scale perfusion cell culture, and its real-time microscopic observation. The system features in maintaining both uniform, and stable chemical or thermal environments, and providing a backflow-free medium pumping, and a precise thermal control functions. In this work, the performance of the medium pumping scheme, and the ITO glass microheater were experimentally evaluated. Results show that the medium delivery mechanism was able to provide pumping rates ranging from 15.4 to 120.0 μL·min−1. In addition, numerical simulation and experimental evaluation were conducted to verify that the ITO glass microheater was capable of providing a spatially uniform thermal environment, and precise temperature control with a mild variation of ±0.3 °C. Furthermore, a perfusion cell culture was successfully demonstrated, showing the cultured cells were kept at high cell viability of 95 ± 2%. In the process, the cultured chondrocytes can be clearly visualized microscopically. As a whole, the proposed cell culture system has paved an alternative route to carry out real-time microscopic observation of biological cells in a simple, user-friendly, and low cost manner.

Thermal therapy and evaluation by a precise temperature control device

AbstractMoxibustion, one of the thermal therapies used in oriental medicine, has several problems, including the fact that temperature distribution over a treatment region is not uniform, the treatment temperature cannot be controlled, and smoke is emitted. To solve these problems, we developed a precise thermal heat transfer control device and applied it to clinical medicine as a substitute for conventional moxibustion. The abdominal heating controller developed in this study has an effect equal to that of moxibustion and can heat the treatment region of human skin uniformly. The treatment effect of the device was evaluated in a clinical experiment, in which we found that these devices can treat ileus, diarrhea, and related disorders. We sought the optimal temperature for thermal therapy with regard to gender, body mass index, and age. We carried out a numerical simulation of temperature distribution inside a human body when the abdominal region is heated. Temperature distribution of the heated abdominal region was calculated using a 2‐D axisymmetric model considering bioheat generation such as blood perfusion and metabolism. The calculation results confirmed that the thermal effect cannot reach the viscera. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/htj.20334

Compact cw Terahertz Spectrometer Pumped at 1.5 μm Wavelength

A compact and low-cost continuous wave terahertz spectrometer operating at an optical wavelength of 1.5 μm is presented. The spectrometer employs high power distributed feedback (DFB) laser diodes in integrated “butterfly” packages. No further optical amplification of the beating signal is required. An integrated photodiode antenna with an output power of 5 μW at 500 GHz is used as efficient terahertz emitter. Employing low-temperature grown (LT-) InGaAs/InAlAs photoconductive receivers as coherent detectors, SNR values of the terahertz power up to 75 dB are attained at an integration time of 300 ms. Accurate characterization of the thermal tuning behavior of the DFBs and precise thermal control yield an absolute accuracy of 1 GHz and a resolution of better than 5 MHz, without any on-line monitoring of the optical frequency. Due to the high frequency resolution no delay line is needed to vary the terahertz phase.

Inexpensive DNA Microarray Application for Screening of Beta-Globin Mutations in Low-Resource Settings.

Abstract 4067Poster Board III-1002Development of public health related products are, in general, driven by clinical usefulness in combination with economic feasibility. Not surprisingly, a high throughput, automated robotic system is not an option in a low-resource setting as exists in the majority of countries with high prevalence of hemoglobinopathies. Diagnostics developed for resource rich areas may not be feasible in such areas but certain parts of these technologies can be transformed into low-cost diagnostics suitable for resource poor settings. Hemoglobinopathies are traditionally presumptively diagnosed using a combination of methods including complete blood count, MCV or MCH, and hemoglobin electrophoresis or HPLC. Recently, sequence specific nucleic acid recognition methodologies have allowed the discovery of more than 200 mutations which cause thalassemia and an even higher number of mutations leading to hemoglobin variants. Importantly, such methods provide a more precise diagnosis and allow for prenatal analysis. Microarrays use specific nucleic acid sequences to detect up to thousands of mutations simultaneously but, due to their cost and requirements of equipment, are principally only suited to resource rich areas. However, pairing microarray technology with alkaline phosphatase colorimetric staining, an established visualization technology, significantly reduces assay cost and initial cost and complexity of required equipment and microarray-based diagnostics can thus become applicable to resource poor settings. This study focused on the development of a highly specific and low-cost method for genotyping beta-thalassemia mutations and hemoglobin variants using colorimetric staining of allele specific DNA microarrays. Target was easily prepared by in vitro incorporation of a small amount of biotin-labeled ribonucleotides after an initial PCR reaction and was immediately ready for subsequent visualization via the well characterized and highly specific biotin-streptavidin interaction. Streptavidin-conjugated alkaline phosphatase coupled to commercially available BCIP/NBT, well established in ELISA and western blots, allowed results visualization. Microarray assays that correctly and accurately identify mutations in multiple nucleic acid sequences (genechips) are difficult to produce as these are usually processed at a single condition. This single condition does not represent the optimum condition for all the individual and necessary reactions required to detect all mutations. This can be circumvented by changing reaction temperature during analysis. This requires multiple readouts during a genotyping cycle and precise thermal control, both of which are not yet compatible with a low-budget application. In a previous paper, we demonstrated a very low cost alternative solution that used buffers with different ionic strength ([Na+]) and a polymeric microfluidic assembly rather than temperature control to optimize microarray conditions. Arrays, including an internal batch quality control, were manufactured on ordinary glass microscope slides coated with a film of agarose. Detection is based on colorimetric grayscale readout from an ordinary flatbed desktop scanner at low resolution (1200 dpi). In this ongoing study, 30 of the most common mutations leading to beta-thalassemia and those responsible for HbC, HbS, HbD-Punjab, HbE and HbO-Arab hemoglobin variants were included. The microarray based technique is currently being compared to molecular diagnosis via sequencing. To date, a 100% concordance has been obtained. The study also continues to optimize probes for mutagenic sites in order to increase the number of analysis sites and confidence in genotype calls. In conclusion, combining a polymeric device easily manufacturable by high volume methods such as injection molding, microarrays printed on ordinary glass slides, and detection based on colorimetric staining a low-budget analysis system for genetic variations was obtained. Start-up and assay costs were roughly $2000 and $5 US, respectively. As such the method provides interesting and new diagnostic possibilities for those third world countries where beta-thalassemia and other hemoglobinopathies are highly prevalent and where the socioeconomic conditions exclude introduction of expensive methods for molecular diagnostics. Disclosures:No relevant conflicts of interest to declare.

A two-dimensional, self-compensated, microthermal cycler for one-step reverse transcription polymerase chain reaction applications

Thermal uniformity within a specific area is a key point for precise thermal control, especially crucial for micro biomedical applications. In this study, a new approach to improve the thermal uniformity inside a specific area was reported and used for reverse transcription polymerase chain reaction (PCR) applications. The temperature uniformity inside the reaction region of a microthermal cycler was significantly enhanced by using array-type microheaters with a two-dimensional, symmetrical, self-compensation (SC) design. With this approach, the edges of thermal profile in the heating area which commonly had significant temperature gradients can be self-compensated with an automatic function. Experimental results from infrared images showed that the percentages of the uniformity area with a thermal variation <1°C were 90.3, 99.9, and 96.8% at three PCR thermocycling temperatures (94, 55, and 72°C, respectively). It was a significant improvement over conventional block-type or serpentine-type microheaters. The performance of this proposed microthermal cycler was successfully verified by amplifying a detection gene associated with the dengue virus serotype 2. The amplification efficiency of the new microthermal cycler was statistically higher than the microheaters without SC function.

GaN MOSFETs with Large Current and Normally-off Operation

GaN is promising for high-power, high-temperature devices due to its large bandgap, high critical electric field, and high saturation velocity compared with Si and SiC. The MOSFET structure can be operated at a positive threshold voltage, namely the normally-off mode, which is preferable for power transistors in terms of fail-safe operation. In order to realize MOSFET operation, good interface quality at SiO2/GaN and low resistance in the n+-contact layer is strongly required. We have overcome these requirements by precise thermal control. Finally, we have fabricated GaN MOSFETs and have achieved more than 1 A operation in the normally-off mode at more than 250oC. The breakdown voltage was more than 1500 V.

OPTIS – A Satellite test of Special and General Relativity

OPTIS has been proposed as a small satellite platform in a high elliptical orbit (apogee 40,000 km, perigee 10,000 km) and is designed for high precision tests of foundations of Special and General Relativity. The experimental set-up consists of two ultrastable Nd:YAG lasers, three crossed optical resonators (monolithic cavities), an ensemble of atomic clocks, an optical comb generator, laser tracking devices and a drag-free control system. OPTIS enables improved tests of (1) the isotropy and (2) constancy of the speed of light, (3) special relativistic time dilation, (4) the universality of the gravitational redshift by comparison of various clocks, can measure (5) the absolute value of the gravitational redshift, (6) the Lense–Thirring effect and (7) the perigee advance and (8) can make a test of a hypothetical Yukawa part in the gravitational potential. To avoid any influence from atmospheric drag, solar radiation, or Earth albedo, the satellite needs drag-free control to depress the residual acceleration down to 10 −14 m/s 2 in the frequency range between 10 −2 and 10 −3 Hz. Precise thermal control must be used to stabilize the cavity temperature to within one part in 10 7 at time scales of 100 s and to one part in 10 5 on the orbit time scale.

4620 技術試験衛星VIII型搭載展開ラジエータに係わるループヒートパイプ内部不凝縮性ガス評価(G06-4 熱反応・物性値,G06 熱工学)

The long life test of a Loop heat pipe in Deployable Radiator (DPR) on the engineering test satellites VIII (ETS VIII) are planned. Non condensable gases with working fluid in a thermal control system such as a loop heat pipe affect the precise thermal control and the performance. The non condensable gas can not be completely excluded from the working fluid in the loop. The hydrogen is one kind of the non condensable gas in the loop. The hydrogen is genereted from corrosion reaction in ammonia. We investigats into the generation of hydorogen in the ammonia and an effect of the non condensable gas.

Conflicts between courtship and thermoregulation: the thermal ecology of amorous male garter snakes (Thamnophis sirtalis parietalis, colubridae).

Thermoregulatory behavior is an important component of daily activities for many reptiles, especially for small heliothermic (sun-basking) species that inhabit cold climates. However, the relative costs and benefits of thermoregulation depend on numerous factors, such that reptiles may sometimes accord a low priority to precise control of body temperatures. We observed and radio tracked garter snakes (Thamnophis sirtalis parietalis) in central Manitoba during the mating season (spring). Previous studies on this species have documented precise behavioral regulation of body temperatures during summer. In contrast, the courting snakes that we studied in springtime spent little time in overt thermoregulatory behavior. Body temperatures were extremely variable (both in outdoor enclosures and in the field) despite abundant opportunities for more precise thermal control. These small elongate reptiles cool so quickly (relative to the time periods needed for effective courtship) that any benefit to higher body temperatures would be transitory at best. Experiments show that hotter males are no better at obtaining matings or at detecting predators. Thus, male garter snakes concentrate on courtship rather than on basking. In the face of conflicting priorities, reptiles may often forgo precise thermoregulation because its benefits are too low, and its costs too high, compared with alternative behaviors.

Transient heat transfer in batch thermal reactors for silicon wafer processing

Precise thermal control of multi-zone batch furnaces has become increasingly important in semiconductor industry to prevent defect generation during device fabrication. This work analyzes fundamental heat transfer processes during fast furnace ramping. Model simulations show two significant thermal features: (1) the radial temperature distribution on wafers follows a universal parabolic profile; and (2) a wafer stack produces a strong cavity effect for thermal radiation. An engineering model is developed based on these features to characterize the dependence of wafer temperature nonuniformity on processing conditions, including the ramp rate and wafer spacing. This simple yet accurate model is useful for real-time process control.

Heat-Treatment Study of Deep-Level Defects in Semi-Insulating Liquid-Encapsulated Czochralski Gallium Arsenide Substrates

Deep-level defects in semi-insulating (S.I.) liquid-encapsulated Czochralski (LEC) GaAs substrates were studied using the thermally stimulated current (TSC) technique. From the heat-treatment temperature dependence of the TSC signal intensity and electrical properties, the thermal behavior of the detected defects with respect to the heat treatment and their correlation to the electrical properties of the substrate were clarified for the first time. The change in the resistivity was closely related to the changes in the TSC signal intensity of T3 (trap depth: 0.31 eV), T6 (0.58 eV) and T x (0.29 eV). The net concentration of these defects changed by 4×1014 cm-3 after heat treatment at 800°C, leading to a threefold increase of the resistivity. Precise thermal control of substrates is very important for consistently obtaining high-quality GaAs substrates.

Segregation effects during growth of pseudo-binary systems with large liquidus-solidus separation

The transport phenomena associated with melt-growth of semi-conductor crystals on Earth and in space were investigated for non-dilute pseudo-binary systems with large liquidus-solidus separation. In these systems, heat and mass transfer are coupled through the dependence of the melting point on composition and the presence of thermosolutal convection. Experimental growth studies of PbSnTe in a vertical Bridgman configuration involving melts with initial aspect ratios of 15 and 6.8 exhibit axial and radial Sn segregation indicative of intensive convective mixing in the melt. The present findings point to the need for more precise thermal field control in crystal growth and suggest growth in a microgravity environment if diffusion controlled conditions are to be achieved. An analysis of heat and mass transfer for an idealized Bridgman growth system has been made and gives predictions for the dynamics that can be expected in such a space experiment.

ATS-6 Significance

The Applications Technology Satellite (ATS-6), the most powerful, most sophisticated, most versatile communications satellite flown to date, is the last of NASA's experimental satellites intended to demonstrate major advances in communications and spacecraft technology. It is a multipurpose, multidisciplinary spacecraft whose principal objectives were to demonstrate a large, unfurlable antenna structure and precise pointing and attitude control in the synchronous orbit The spacecraft carries 27 different experiments, 3 of which demonstrate users' applications of satellite communications. Significant advances in antenna technology, precise attitude control, materials technology, spacecraft structures, and thermal control have been successfully demonstrated. The most significant accomplishments of the ATS-6 mission are the demonstration of the practicality of satellite broadcasting to small, simple, inexpensive ground stations and the uses of this potential service in the solution of social problems involving education and health care. The success of these initial demonstrations has led ATS-6 experimenters and potential users to incorporate a Public Service Satellite Consortium dedicated to the provision of satellite broadcasting services for educational and health-care applications.

A Simple Evaporative System for Space-Environmental Thermal Control of Electronic Components

A passive mass transfer thermodynamic device employing the latent heat of vaporization of an enclosed liquid is described as a method of precise thermal control for single, low-mass, high-energy electronic components. This device has particular application for electronic components having high power density which are incorporated in spacecraft electronic systems relying otherwise on radiant exchange with the environment as a means of space-environmental thermal control. Specific areas of interest growing out of the design requirements for such a mass transfer device are 1) liquid ullage control under zero-g conditions, precluding loss of liquid due to blow-out, and 2) favorable exploitation of liquid adsorption and surface phenomena in maintaining a continuous heat-sinking effect. The latter effect is demonstrated by data obtained in operating appropriately instrumented thermal control test articles under one-g conditions in vacuum and non-vacuum environments. Satisfactory heat-sinking is demonstrated over a range of energy inputs. Application of the system methodology and capabilities to the problem of space-environmental thermal control is evaluated and summarized.