Thermal Modulation Research Articles

Kinetic Modeling in Temperature-Modulated Semiconductor Gas Sensor Utilizing Eley-Rideal Mechanism and Its Application in Discriminative Detection of VOCs.

This study presents a comprehensive kinetic investigation for describing the dynamic sensing process of semiconductor metal oxide (SMO)-based gas sensors, with a focus on the Eley-Rideal mechanism as a valid pathway. The modeling elucidates the direct interactions between volatile organic compounds (VOCs) and adsorbed oxygen on the material surface, providing insights into the temperature-dependent response characteristics of the sensor and addressing selectivity toward different VOCs fundamentally. By incorporating the effects of thermal modulation, the kinetic model was validated through theoretical fitting of experimental data obtained from a fabricated SnO2 nanoparticle gas sensor exposed to ethanol, n-propanol, toluene, and butanone at systematically varying operating temperatures. The results demonstrated that the model accurately captures response transient values, enabling a general framework for qualitatively discriminating specific gases based on their unique reaction kinetics. Furthermore, a machine learning procedure containing the above model and power laws of quantitative concentrations after identifying compounds was developed for the prediction of target VOCs. The qualitative accuracy was determined to be 99.4%, while quantifying with the mean absolute errors of 5.0, 7.5, 4.0, and 8.9 within the range of 25-200 ppm, respectively. The precise and straightforward strategy facilitates the response modeling of SMO-based gas sensors, offering a valuable platform for the designing model-driven algorithms applicable in gas analysis and monitoring.

Ultrafast thermal modulation dynamics during ripple formation induced by a femtosecond laser multi-pulse vortex beam

Abstract This work theoretically investigated the ultrafast thermal modulation dynamics during early formation of ripples on an Au film induced by femtosecond laser multi-pulse vortex beam irradiation. An extended two-temperature dynamics model that comprehensively considers optical interference modulation for the formation of seed ripples, transient reflectivity and non-equilibrium thermal transfer was self-consistently built to predict high-contrast ripple formation. The two-dimensional evolution of electron and phonon temperature modulations during ripple formation in a high non-equilibrium state of Au film were obtained via femtosecond laser multi-pulse vortex beam irradiation. It was revealed that ripple contrast can be significantly amplified by shortening the laser wavelength, increasing the pulse number, or enlarging the laser fluence of the vortex beam. Moreover, the electron–phonon coupling time during ripple formation is fully explored in detail. This study provides valuable insights into optimizing laser parameters for controlled high-contrast ripple formation on Au films.

An Overview of the R&D of Flywheel Energy Storage Technologies in China

The literature written in Chinese mainly and in English with a small amount is reviewed to obtain the overall status of flywheel energy storage technologies in China. The theoretical exploration of flywheel energy storage (FES) started in the 1980s in China. The experimental FES system and its components, such as the flywheel, motor/generator, bearing, and power electronic devices, were researched around thirty years ago. About twenty organizations devote themselves to the R&D of FES technology, which is developing from theoretical and laboratory research to the stage of engineering demonstration and commercial application. After the research and accumulation in the past 30 years, the initial FES products were developed by some companies around 10 years ago. Today, the overall technical level of China’s flywheel energy storage is no longer lagging behind that of Western advanced countries that started FES R&D in the 1970s. The reported maximum tip speed of the new 2D woven fabric composite flywheel arrived at 900 m/s in the spin test. A steel alloy flywheel with an energy storage capacity of 125 kWh and a composite flywheel with an energy storage capacity of 10 kWh have been successfully developed. Permanent magnet (PM) motors with power of 250–1000 kW were designed, manufactured, and tested in many FES assemblies. The lower loss is carried out through innovative stator and rotor configuration, optimizing magnetic flux and winding arrangement for harmonic magnetic field suppression. Permanent magnetic bearings with high load ability up to 50–100 kN were developed both for a 1000 kW/16.7 kWh flywheel used for the drilling practice application in hybrid power of an oil well drilling rig and for 630 kW/125 kWh flywheels used in the 22 MW flywheel array applied to the flywheel and thermal power joint frequency modulation demonstration project. It is expected that the FES demonstration application power stations with a total cumulative capacity of 300 MW will be built in the next five years.

High-performance floating thermoelectric generator for all-day power supply

Thermoelectric generators (TEGs) offer notable benefits in harnessing diverse low-grade waste heat from the environment. However, the uninterrupted capture of these energy resources still remains a huge challenge. Herein, we have developed a temperature-adaptive floating thermoelectric generator (TAFTEG) by integrating a temperature-adaptive absorber/emitter (TAA/E) to synergistically exploit renewable energy from the sun, outer space, and the water bodies by leveraging diurnal spectrally selective absorption and nocturnal radiative cooling. The WxV1-xO2-based TAA/E demonstrates remarkably solar absorption of ∼96 % and a superior switching ability of dynamic thermal radiation modulation from the low emission of ∼45 % to high emission of ∼81 %. Assembled with 8 pairs of Bi2Te3-based TEG legs, the TAFTEG enables a stable temperature difference of 34°C under indoor solar irradiation (1 kW m−2), yielding a peak power output of ∼1.0 mW cm−2, and continuous all-day power supply under both clear and overcast conditions. This strategy paves a new avenue toward the round-the-clock power supply from ambient environments.

Dynamic optical and thermal modulation of electrochromic smart windows and sunglasses based on benzothiadiazole-extended viologen derivatives

Dynamic optical and thermal modulation of electrochromic smart windows and sunglasses based on benzothiadiazole-extended viologen derivatives

Quantitative characterisation of debris cloud-induced pitting damage in AL-Whipple shields of spacecraft using infrared thermography

ABSTRACT Quantitatively evaluating the debris cloud-induced pitting damage in the AL-Whipple structure of spacecraft, is still a challenge, let alone microstructural plastic deformation usually accompanied by geometric cratering defects, which may decrease material stress-carrying capacity and structural life. With this motivation, a dedicated modelling technique is proposed to gain an insight into various modalities (i.e., geometric and plastic defects) of pitting damage-induced thermal modulation for infrared inspection. Then, a sequence of infrared images is obtained and analysed using the gap smoothing algorithm and naive Bayes classification methods. On this basis, a quantitative characterization framework is proposed to characterize the damage modalities and their morphologies. This method is validated using a 3D numerical model which contains pitting damage acquired from the real-world structure. Modality classification and morphology evaluation results are well consistent with the artificial defects, in terms of the modality, diameter, and depth. Then they‘re experimentally corroborated, in which the severity and distribution of pitting damage are precisely characterized, in terms of the crater number and morphologies, as well as the size of plastic regions around these craters, which are consistent with the actual observations. This work proposes a non-destructive strategy for pitting damage evaluation, which is engineering-friendly.

A Wide Color Gamut and Noniridescent Zinc-Anode Asymmetric Electrochromic Device for Self-Sustaining Color-Adaptive Bio-Camouflage System.

Inspired by camouflage-colored organisms, the development of bio-camouflage systems using electrochromic (EC) technology has gained significant interest. However, existing EC systems struggle with achieving a wide color gamut, noniridescent colors, and self-sustainability. Herein, a self-sustainable color-adaptive bio-camouflage system integrating EC and nanogenerator (NG) technologies, enabling environmental color adaptation, and thermal regulation without an external power source is proposed. The system is based on a zinc-anode EC device (ZECD) with an asymmetric structure, incorporating flexible tungsten oxide and vanadium oxide electrodes. During the EC process, tungsten oxide shifts between blue and transparent, allowing near-infrared thermal modulation, while the vanadium oxide transitions from yellow to transparent. This design enables reversible near-infrared modulation and noniridescent color conversion among black, blue, green, yellow, and transparent. For the self-sustainability of the system, an electromagnetic and triboelectric hybrid NG that collects biomechanical energy is developed. In a typical driven cycle, the integrated system transitions colors and achieves significant near-infrared spectral modulation, demonstrating environmental adaptability and thermal regulation. Experiments on human skin and simulated chameleon color changes further confirm the system's effectiveness. This work highlights the potential of integrating EC and NG technologies to advance color-adaptive camouflage systems, opening new an avenue for bio-camouflage design.

Translating 2D-Chromatographic Fingerprinting to Quantitative Volatilomics: Unrevealing Compositional Changes in Maize Silage Volatilome for Robust Marker Discovery.

This study examines the complex volatilome of maize silage, both with and without commercial heterolactic strain inoculation, conserved for 100 days, using quantitative volatilomics. Chemical classes linked to microbial metabolism were analyzed across a concentration range from 10 μg g-1 to 1 ng g-1. A reference method using comprehensive two-dimensional gas chromatography (GC × GC) and time-of-flight mass spectrometry (TOF MS) with loop-type thermal modulation (TM) was translated to a differential-flow modulation (FM) platform with parallel MS and flame ionization detector (FID) detection. With translation, the original method's analyte elution order and resolution are preserved. The new method allowed for accurate quantification using multiple headspace solid-phase microextraction (MHS-SPME) and FID-predicted relative response factors (RRFs). Both methods showed comparable discriminatory power with FM GC × GC-MS/FID achieving satisfactory quantification accuracy without external calibration. Analysis of 98 volatiles provided insights into silage fermentation, supporting marker discovery and correlations with silage quality and stability.

Unraveling the impact of thermal modulation in heating and cooling dies on the fibrous structure of high-moisture meat alternatives

We aimed to create high-moisture plant-based meat alternatives (HPMAs) that closely mimic the fibrous structure found in conventional meat. To achieve this goal, we focused on the impact of modulating the heating and cooling die temperatures during the extrusion process on the structural properties of HPMAs. The optimal temperatures for the heating and cooling dies were determined to be 160 and 50 °C, respectively, following a comprehensive analysis of various quality characteristics. These included assessments of cutting strength, texturization degree, moisture content, and microstructure. Analyzing the correlation coefficients between heating and cooling die temperatures and the quality characteristics of HPMAs revealed that modulating the cooling die temperature has a greater impact on quality characteristics than modulating the heating die temperature. The quality characteristics of HPMAs were also compared with those of boiled and sous-vide cooked chicken breasts. The optimal HPMA exhibited the most similar fibrous macro- and micro-structure to sous-vide cooked chicken breast. Consequently, our study highlights the importance of modulating the heating die and cooling die temperatures, among various process parameters of high-moisture extrusion cooking, which is crucial for producing HPMAs closely resembling conventional meat.

Pillar-Pore-Structured Nanophotonic Coating with Superior Solar and Thermal Modulation Abilities

Pillar-Pore-Structured Nanophotonic Coating with Superior Solar and Thermal Modulation Abilities

The low-dimensional units modulation of 3D floral Fe/Ni@C towards efficient microwave absorption

Metal-organic frameworks (MOF) derivatives have great potential in microwave absorption (MA) due to their customizable components, topology, and high porosity. However, the correlation between the structural parameters of the low-dimensional units and the MA performance of the 3D MOF derivatives remains unclear. Herein, we prepared a series of floral Fe/Ni@C with different petal sizes and aspect ratios to investigate the effect of low-dimensional structural parameters on the MA properties of 3D MOF derivatives. Specifically, we proposed a competitive coordination strategy. By adjusting the ratio of coordination metals, we successfully obtained floral FeNi-MOF-74 with different petal sizes and aspect ratios. Subsequently, the floral Fe/Ni@C was obtained by thermal-field modulation. It shows that, on the one hand, as the petal size increases, the conductive path is extended and the electron hopping is enhanced, thus facilitating the conductivity loss. And, with the rise of the petal aspect ratio, the tip effect is enhanced, which strengthens the polarization loss. On the other hand, the graphitization degree of the carbon components as well as the size and magnetic properties of the alloy particles can be effectively modulated by optimizing the thermal field modulation temperature. Noteworthily, under the conditions of a coordination metal ratio of 1:1 and an annealing temperature of 700 °C, the obtained MOF derivative exhibited excellent microwave absorption (−65.47 dB at 1.56 mm) and broadband (6.09 GHz at 1.76 mm). This strategy provides new ideas for modulating the microstructure and electromagnetic properties of MOF derivatives.

Bioinspired smart dual-layer hydrogels system with synchronous solar and thermal radiation modulation for energy-saving all-season temperature regulation

All-season thermal management with zero energy consumption and emissions is more crucial to global decarbonization over traditional energy-intensive cooling/heating systems. However, the static single thermal management for cooling or heating fails to self-regulate the temperature in dynamic seasonal temperature condition. Herein, inspired by the dual-temperature regulation function of the fur color changes on the backs and abdomens of penguins, a smart thermal management composite hydrogel (PNA@H-PM Gel) system was subtly created though an “on-demand” dual-layer structure design strategy. The PNA@H-PM Gel system features synchronous solar and thermal radiation modulation as well as tunable phase transition temperatures to meet the variable seasonal thermal requirements and energy-saving demands via self-adaptive radiative cooling and solar heating regulation. Furthermore, this system demonstrates superb modulations of both the solar reflectance (ΔR = 0.74) and thermal emissivity (ΔE = 0.52) in response to ambient temperature changes, highlighting efficient temperature regulation with average radiative cooling and solar heating effects of 9.6 °C in summer and 6.1 °C in winter, respectively. Moreover, compared to standard building baselines, the PNA@H-PM Gel presents a more substantial energy-saving cooling/heating potentials for energy-efficient buildings across various regions and climates. This novel solution, inspired by penguins in the real world, will offer a fresh approach for producing intelligent, energy-saving thermal management materials, and serve for temperature regulation under dynamic climate conditions and even throughout all seasons.

Solar regulation based on thermofluorescence and thermochromism for self-adaption of temperature

A novel solar regulation theory is proposed based on thermofluorescence and thermochromism for the first time. The solar absorption can be enhanced/suppressed by the turned-off/turned-on fluorescence and the broadband/narrowband high/low absorptivity at a low/high temperature. Based on this, a new daytime temperature-adaptive film is proposed, whose solar regulation ratio is up to 21.38 %, higher than those of the thermochromism-only film and most reported thermochromic microcapsules based films. Under the strongest solar irradiance, a maximal heating temperature of 8.15 °C can be achieved in winter, and a cooling temperature of 2.23 °C can be obtained in summer, showing very good temperature adaption. Combining this solar regulation with thermal emission modulation, a new all-day temperature-adaptive film is proposed. In winter, its heating performance is greatly enhanced during the day with a heating temperature reaching 14.26 °C, 6.11 °C higher than that of the daytime temperature-adaptive design, while its cooling performance is significantly suppressed during the night with an average cooling temperature of 1.56 °C, much lower than that of the daytime temperature-adaptive design. Total energy savings is improved globally, especially in the cold high-latitude regions. This research provides insights into the design of new and high-performance temperature-adaptive films, facilitating advancements in this field.

Multifunctional Radiation Conditioning Emitter for Laser and Infrared with Adaptive Radiative Cooling.

With the development of technology, multifunctional multiband emitters have been paid much attention due to their wide range of applications, such as LIDAR detection, spectroscopic sensing, and infrared thermal management. However, the development of such emitters is impeded by incompatible structural requirements of different electromagnetic wavebands. Here, we demonstrate coupled modulation between near-infrared (NIR) laser-wavelength and long-wavelength-infrared by constructing a multifunctional emitter (MFE) with a structure of Al/HfO2/VO2, utilizing the phase transition of VO2. The MFE displays excellent thermal modulation capability within the 8-14 μm range, achieving a thermal insulation effect (ε8-14μm = 0.18) at low temperatures, and heat dissipation effect (ε8-14μm = 0.64) at high temperatures. The MFE's radiation power regulation capability is 145.06 W m-2 between a temperature of 0 to 60 °C. Moreover, the MFE possesses a large reflectivity modulation value of 0.78 at NIR laser-wavelength (1.06 μm) with a short phase transition time of 1003 ms under 3 W cm-2 laser irradiation. This study provides a guideline for the coordinated control of electromagnetic waves and intelligent collaborative thermal management through simple structural design, thus, having broad implications in energy saving and thermal information processing.

Non-Isothermal Operation of Membrane Electrode Assembly-Based CO2 Electrolyzer for Enhanced Energy Efficiency

The utilization of membrane electrode assemblies (MEA) in carbon dioxide (CO2) electrochemical conversion showcases the promising potential for stable and scalable industrial applications in fuel production, attributed to efficient gas diffusion and minimized system resistance. The electrochemical performance of MEA-based CO2 electrolyzers relies on the chemical reactivity and product selectivity optimization which is dependent on three factors: CO2 mass transport, charge transport, and ionic transport. Elevating the overall system temperature benefits the performance of the oxygen evolution reaction (OER) at the anode. Furthermore, the elevated temperature enables higher conductivity of anion exchange membranes (AEM), thereby further diminishing cell voltage. However, the downside emerges as CO2 solubility decreases at higher temperatures, fostering a scenario where the catalytic reaction leans toward hydrogen evolution, thereby undermining product selectivity.Herein, we propose an innovative approach involving thermal management for separate temperature control for the anode and cathode, forming a non-isothermal MEA by maintaining an elevated anodic temperature while cooling the cathode. This approach simultaneously addresses the need for a high-temperature anode and a low-temperature cathode. This study exhibits a temperature gradient of approximately 20°C between the anodic and cathodic planes achieved through efficient thermal modulation of water cooling and heating within the electrode plates.We showcase the benefit of non-isothermal operation with an Ag-based cathode and IrO2-based anode using 1 M KOH as the anolyte for CO2 conversion into CO. The non-isothermal condition, i.e., maintaining an anodic temperature of 80°C and a cathode temperature of 60oC, demonstrated a 65% enhancement in CO partial current density (j co), 195.6 mA cm-2, compared to the isothermal 80°C condition, 118.6 mA cm-2. The optimal performance across all temperature regimes is found to be the non-isothermal condition with anode temperature at 60°C and cathode temperature at 40 oC, yielding a j co of 243.5 mA cm-2 at 3.25 V, marking a 13.3% improvement over the isothermal 60°C condition (j co = 214.9 mA cm-2). The increase in the j co can be attributed to the lower temperature at the cathode (40 oC for the non-isothermal condition vs. 60oC for the isothermal ccondition) resulting in higher CO faradaic efficiency.The CO faradaic efficiency remained above 80% (cell potential < 2.7V) for the non-isothermal 60°C condition, whereas it dropped below 80% throughout the entire region cell potential range for the isothermal 60°C condition. This study presents a novel non-isothermal operation for advanced thermal management for MEA-based CO2 electrolyzers for simultaneous enhancement in anode activity as well as cathode selectivity. We believe this thermal management strategy is promising for engineering high-performing MEA-based CO2 electrolyzers at industrial scales.

Low-loss silica waveguide 1×8 thermo-optic switch based on large-scale multimode interference couplers

Optical switches play key role in signal crossing and interconnection. Low-loss and compact optical switches are highly demanded in on-chip optical routing. A silica waveguide 1 × 8 thermo-optic switch based on cascaded 1 × 8 multimode interference (MMI) and 8 × 8 MMI couplers is experimentally demonstrated. Beam propagation method is adopted in the theoretical design and optimization. Standard CMOS technology fabrication is used in switch preparation. Air trenches are introduced to enhance the thermal modulation. At wavelength 1550 nm, the measured insertion loss and crosstalk of this 1 × 8 switch is less than 3.69 dB and −16.29 dB, respectively. And the extinction ratio is larger than 16.68 dB for all routing states. The rise time and fall time are 1.0 ms and 1.24 ms respectively. Compared with the 8-channel switch based on cascaded stages structure, the size reduces by 30 %. With future bandwidth improvement, this demonstrated switch has good potentials in the application of all-optical network routing.

Chemisorption of hydrogen on metal oxides with palladium (II) oxide additives

Chemisorption can lead to a change in electrical conductivity, which allows using semiconductor materials to create gas sensors. On the other hand, semiconductor sensors can be used as devices for studying the chemisorption of gases. In this work, we set two tasks. The first of them was to create a sensor for the selective determination of hydrogen in air, including in a mixture with other gases. The second task was to determine the mechanism of hydrogen chemisorption on the surface of metal oxides with palladium (II) oxide additives. We obtained and characterised nanodispersed materials based on SnO2 and WO3 with additions of 3% PdO by weight. We compared the electrical characteristics of these materials in stationary temperature conditions as well as with temperature modulation in the presence of hydrogen, methane, and their mixtures. The specific features of hydrogen chemisorption were determined on the surface of metal oxide semiconductors based on SnO2 and WO3 with PdO additives in the temperature modulation mode of the sensor. It was shown that the extrema in the dependence of the sensor’s electrical conductivity on temperature can be explained by the contribution of proton transfer to the total electrical conductivity. The presence of extrema in the electrical conductivity of sensors, which were observed in thermal modulation mode in the presence of hydrogen, allows conducting qualitative and quantitative analysis of not only single-component gas systems, but also of mixtures of hydrogen with other analyte gases. In particular, this work demonstrated that it was possible to determine the composition of a hydrogen-methane mixture in air using a single metal oxide sensor. The advantage of this approach is that multidimensional data arrays can be easily processed.

Recent advances in vanadium dioxide for dynamic thermal radiation modulation: A review

Thermal radiation of materials can be manipulated for the necessary applications in thermal management and infrared camouflage. To our knowledge, controlling surface emissivity is crucial for modulating thermal radiative energy, therefore, dynamic modulation of emissivity has received more attention. Vanadium dioxide (VO2) stands out as a highly promising candidate due to its capacity for reversible transition from monoclinic VO2(M) to rutile VO2(R) near room temperature. This transition results in a rapid change from transparent to opaque within the mid-infrared spectrum accompanied by a reduction in emissivity. This review offers an overview of recent progresses in the dynamic control of thermal radiation of the surface by using VO2. It also summarizes the preparation, modulation mechanisms, and applications of positive and negative differential emissivity devices. Finally, the challenges and opportunities in advancing research on VO2-based smart devices are discussed.

Development and analysis of an artificial olfactory bulb

This article presents the development of an artificial olfactory bulb (OB) using an electronic nose with thermally modulated metal-oxide sensors. Inspired by animal OBs, our approach employs thermal modulation to replicate the spatial encoding patterns of glomeruli clusters and subclusters. This new approach enhances the classification capabilities of traditional electronic noses and offers new insights for biomimetic olfaction. Molecular receptive range (MRR) analysis confirms that our artificial OB effectively mimics the glomerular distribution of animal OBs. Additionally, the incorporation of a short axon cell (SAC) network, inspired by the animal olfactory system, significantly improves lifetime sparseness and qualitative ability of the artificial OB through extensive lateral inhibition, providing a theoretical framework for enhanced olfactory performance.

A nanoscale photonic thermal transistor for sub-second heat flow switching

Control of heat flow is critical for thermal logic devices and thermal management and has been explored theoretically. However, experimental progress on active control of heat flow has been limited. Here, we describe a nanoscale radiative thermal transistor that comprises of a hot source and a cold drain (both are ~250 nm-thick silicon nitride membranes), which are analogous to the source and drain electrodes of a transistor. The source and drain are in close proximity to a vanadium oxide (VOx)-based planar gate electrode, whose dielectric properties can be adjusted by changing its temperature. We demonstrate that when the gate is located close ( < ~1 µm) to the source-drain device and undergoes a metal-insulator transition, the radiative heat transfer between the source and drain can be changed by a factor of three. More importantly, our nanomembrane-based thermal transistor features fast switching times ( ~ 500 ms as opposed to minutes for past three-terminal thermal transistors) due to its small thermal mass. Our experiments are supported by detailed calculations that highlight the mechanism of thermal modulation. We anticipate that the advances reported here will open new opportunities for designing thermal circuits or thermal logic devices for advanced thermal management.