Thermal Modulation Research Articles

Autonomous Thermal Modulator Based on Gold Film‐Coated Liquid Crystal Elastsomer

AbstractRadiative cooling has been recently intensively explored for thermal management and enhancing energy efficiency. Yet, traditional materials with singular emissivity fall short in dynamic thermal management, highlighting the need for materials that can adjust their thermal radiation in real time. Active modulation methods, requiring external stimuli such as mechanical stretch, electric potential, or humidity change, offer adaptability but can increase energy use and complexity. Passive approaches, using materials' inherent thermal‐responsive properties, face manufacturing and scalability challenges. Here, a scalable yet effective passive approach is introduced for adaptive thermal modulation based on gold (Au) and liquid crystal elastomer (LCE) with a reversible response to environmental temperature changes. This modulator enables a “low thermal resistance” state through actuation‐induced microcracks that expose a high‐emissivity polymer substrate, and a “high thermal resistance” state by closing these microcracks and forming a high thermal resistance air gap between the modulator and the target object. The flexible design and fixed external dimensions of the Au‐LCE thermal modulator make it adaptable to various surface geometries. Furthermore, by adjusting the LCE's chemical composition, the modulator's transition temperature can be tailored, broadening its applications from enhancing building energy efficiency to improving clothing thermal comfort.

Microsecond-pulsed CO2 laser cleaning of high damage threshold fused silica

Ultraviolet (UV) laser-induced damage from defects and impurities in conventional ground and polished fused silica optics significantly hinders their application in high-power laser systems. Laser cleaning, as a non-contact and polishing fluid-free technology, is likely to be a key technology for improving the damage performance of fused silica optics. However, conventional laser cleaning primarily focuses on surface pollution without removing the material. It overlooks the detrimental effects of multiscale defects and impurities inside the fused silica. In this study, microsecond-pulsed CO2 laser cleaning was proposed to enhance the laser-induced damage threshold (LIDT) by ablating fused silica to nanometer depths. Through multiple-scale simulations, the thermal stress evolution and modulation mechanism of defects and impurities on the damage performance (ranging from the macro- to nanoscale) were revealed. Utilizing multimodal characterization, laser cleaning effectively eliminated and suppressed surface/subsurface defects, absorptive defects, chemical structural defects, and elemental impurities without introducing residual thermal stress and destroying surface roughness. In addition, the evolution of the molecular structures indicated a tendency for intrinsic defects to recombine into shorter-ring structures, which resulted in a densified fused silica surface. The laser-cleaned samples exhibited higher damage thresholds, achieving 47.6 % (0 % probability) and 27.0 % (100 % probability) improvements compared with uncleaned samples. This technology provides a new method for fabricating high damage threshold fused silica optics with superior surface quality for high-power laser applications.

Thermal modulation of energy allocation during sex determination in the European sea bass (Dicentrarchus labrax)

Water temperature governs physiological functions such as growth, energy allocation, and sex determination in ectothermic species. The European sea bass (Dicentrarchus labrax) is a major species in European aquaculture, exhibiting early dimorphic growth favoring females. The species has a polygenic sex determination system that interacts with water temperature to determine an individual’s sex, with two periods during development that are sensitive to temperature. The current study investigated the influence of water temperature on energy allocation and sex-biased genes during sex determination and differentiation periods. RNA-Sequencing and qPCR analyses were conducted in two separate experiments, of either constant water temperatures typical of aquaculture conditions or natural seasonal thermal regimes, respectively. We focused on eight key genes associated with energy allocation, growth regulation, and sex determination and differentiation. In Experiment 1, cold and warm temperature treatments favored female and male proportions, respectively. The RNA-seq analysis highlighted sex-dependent energy allocation transcripts, with higher levels of nucb1 and pomc1 in future females, and increased levels of egfra and spry1 in future males. In Experiment 2, a warm thermal regime favored females, while a cold regime favored males. qPCR analysis in Experiment 2 revealed that ghrelin and nucb1 were down-regulated by warm temperatures. A significant sex-temperature interaction was observed for pank1a with higher and lower expression for males in the cold and warm regimes respectively, compared to females. Notably, spry1 displayed increased expression in future males at the all-fins stage and in males undergoing molecular sex differentiation in both experimental conditions, indicating that it provides a novel, robust, and consistent marker for masculinization. Overall, our findings emphasize the complex interplay of genes involved in feeding, energy allocation, growth, and sex determination in response to temperature variations in the European sea bass.

Thermal Modulation of Resistance Gas Sensor Facilitates Recognition of Fragrance Odors

Herein, we prepared two different MOS-based gas sensors with integrated micro-hotplates. The two sensors were employed to detect various fragrances (cedar, mandarin orange, rose A, and rose B), exhibiting similarly great sensing performances. The gas sensing properties of the MOS-based sensor depend on the sensor’s operating temperature. In addition to isothermal operation, various pulse heating modes were applied to investigate the gas sensing performances with respect to the four fragrances. Multivariate gas sensing features of the four fragrances were obtained under different operating modes, which were utilized for the recognition of fragrance odors successfully, based on the long short-term memory (LSTM) algorithm.

Metamaterial terahertz device with temperature regulation function that can achieve perfect absorption and complete reflection conversion of ultrawideband

The field of terahertz devices is important in terahertz technology. However, most of the current devices have limited functionality and poor performance. To improve device performance and achieve multifunctionality, we designed a terahertz device based on a combination of VO2 and metamaterials. This device can be tuned using the phase-transition characteristics of VO2, which is included in the triple-layer structure of the device, along with SiO2 and Au. The terahertz device exhibits various advantageous features, including broadband coverage, high absorption capability, dynamic tunability, simple structural design, polarization insensitivity, and incident-angle insensitivity. The simulation results showed that by controlling the temperature, the terahertz device achieved a thermal modulation range of spectral absorption from 0 to 0.99. At 313 K, the device exhibited complete reflection of terahertz waves. As the temperature increased, the absorption rate also increased. When the temperature reached 353 K, the device absorption rate exceeded 97.7% in the range of 5–8.55 THz. This study used the effective medium theory to elucidate the correlation between conductivity and temperature during the phase transition of VO2. Simultaneously, the variation in device performance was further elucidated by analyzing and depicting the intensity distribution of the electric field on the device surface at different temperatures. Furthermore, the impact of various structural parameters on device performance was examined, offering valuable insights and suggestions for selecting suitable parameter values in real-world applications. These characteristics render the device highly promising for applications in stealth technology, energy harvesting, modulation, and other related fields, thus showcasing its significant potential.

Unveiling the magic of twist angle: Thermal transport in Two-dimensional Graphene/MoS2/Graphene Heterostructures

Thermal transport properties of two-dimensional vdW heterostructures have attracted considerable research interests in electron-related devices due to their powerful capability of multi-functional integration. Herein, we investigated the in-plane and out-of-plane thermal conductivity of graphene/MoS2 heterostructures under various twist angles utilizing molecular dynamics simulations. It was found that the in-plane thermal conductivity of MoS2 layer in heterostructures decreases with twist angle. Notably, the lowest thermal conductivity occurs at a twist angle of 10.893°, just 47.3 % of that in untwisted MoS2 layers in heterostructure. In addition, the interlayer interfacial thermal resistance between graphene and MoS2 layer increases with the twist angle but decreases with the layer numbers of graphene. The atomic position deviation, potential energy surface, phonon state of density are calculated to reveal the regulation mechanism of thermal conductivity by twist angle. Interestingly, it is found that the twist angles and the layer numbers of graphene can control the atomic vibration arising from potential energy surfaces and phonon transport through the overlap of phonon density of states between graphene and MoS2 layers. This study can provide valuable insights into the thermal conductivity modulation and phonon transport mechanism of heterostructures.

Analysis of an existing hydrocarbon gas pipeline for conversion to dense phase CO2 service

Esso Australia is investigating the feasibility of a carbon capture and storage (CCS) project in East Gippsland, Victoria. Known as the South-East Australia Carbon Capture and Storage (SEA CCS) Hub, the project aims to re-purpose existing infrastructure and offshore depleted hydrocarbon reservoirs to store carbon dioxide (CO2). The project aims to reduce greenhouse gas emissions from Esso’s Longford Gas Conditioning Plant, and to unlock future CCS opportunities for Australia. One option identified as part of the SEA CCS feasibility was to convert part of the existing onshore section of the Barracouta 450 mm gas pipeline to Longford Gas Plant (BTA450-LFD), Licence PL/1 under the Victorian Pipeline Act, to dense phase CO2 service. This paper documents the initial findings of the potential for the onshore section of the BTA450 for conversion, with particular emphasis on brittle and ductile fracture control considerations. In summary, when attempting to convert existing hydrocarbon gas pipelines for CO2 service, operators need to undertake an appropriate assessment of fracture control considerations. The insights of this paper may serve as a useful guide document for assessing other existing onshore pipelines for CO2 service conversion. Due to the thermal modulation effect of the surrounding water for subsea pipelines, this guidance does not apply to subsea pipeline sections.

Active control of nonreciprocal near-field radiative heat transfer with a drift-current biased graphene/α-MoO3 heterostructure.

The interaction between the drift-current biased graphene plasmonics and the hyperbolic phonon polaritons of α-MoO3 provides a promising way to manipulate near-field radiation heat transfer (NFRHT). Through examination of the drift biased graphene/α-MoO3 heterostructure, it has been discovered that drift-current applied to the graphene effectively enhances photon tunneling. Consequently, they dynamically modulate the coupling effect of the two excitations, thereby offering a reliable pathway for the modulation of NFRHT. Furthermore, the influencing mechanism of vacuum gaps on nonreciprocal NFRHT with different drift-current rates is revealed, and it is discovered that the vacuum gaps can filter the nonreciprocal surface plasmon polaritons with high nonreciprocity. Our findings make it possible to manipulate nanoscale thermal rectification and noncontact thermal modulation.

Wide-range thermal conductivity modulation based on protonated nickelate perovskite oxides

The perovskite oxides ReNiO3 (Re = rare-earth elements) are promising functional materials due to their strongly correlated electrons. Except for the well-known intrinsic metal-insulating transition in these materials, recent progresses have proved that protonation of ReNiO3 can bring about interesting Mott transition in this series. To date, in these protonated species (H-ReNiO3), huge resistance switching, fast ionic diffusion, and their applications as an iontronic transistor, memristor, and fuel cell are reported. In this work, the thermal conductivities of H-ReNiO3 (Re = La, Nd, Sm, and Eu) epitaxial thin films are investigated. The protonation-induced Mott transition can effectively modulate the electronic thermal conductivity while the lattice thermal conductance is less affected. Hence, at room temperature, the metallic LaNiO3 and NdNiO3 exhibit reversible wide thermal conductivity modulation, in ranges of 2.6–12.0 and 1.6–8.0 W m−1 K−1, respectively. These values are much larger than other thermal regulation materials based on transition metal oxides. Thus, our work reveals the great potential of ReNiO3 being applied as a thermal-regulating material. The fast ionic diffusion in H-ReNiO3 also guarantees that a fast response and wide-range thermal transistor can be realized by H-LaNiO3 and H-NdNiO3 in the future.

Thermal-Rectified Gradient Porous Polymeric Film for Solar-Thermal Regulatory Cooling.

Solar-thermal regulation concerning thermal insulation and solar modulation is pivotal for cooling textiles and smart buildings.Nevertheless, a contradiction arises in balancing the demand to prevent external heat infiltration with the efficient dissipation of excess heat from enclosed spaces. Here, a concentration-gradient polymerization strategy is presented for fabricating a gradient porous polymeric film comprising interconnected polymeric microspheres. This method involves establishing an electric field-driven gradient distribution of charged crosslinkers in the precursor solution, followed by subsequent polymerization and freeze-drying processes. The resulting porous film exhibits a significant porosity gradient along its thickness, leading to exceptional unidirectional thermal insulation capabilities with a thermal rectification factor of 21%. The gradient porous film, with its thermal rectification properties, effectively reconciles the conflicting demands of diverse thermal conductivity for cooling unheated and spontaneously heated enclosed spaces. Consequently, the gradient porous film demonstrates remarkable enhancements in solar-thermal management, achieving temperature reductions of 3.0 and 4.1°C for unheated and spontaneously heated enclosed spaces, respectively, compared to uniform porous films. The developed gradient-structured porous film thus holds promise for the development of thermal-rectified materials tailored to regulate solar-thermal conditions within enclosed environments.

Structural color tunable intelligent mid-infrared thermal control emitter

This work proposes a colored intelligent thermal control emitter characterized by adjustable structural color development with a reflection spectrum in the visible light range and intelligent thermal control with temperature switching in the mid infrared wavelength band. In the beginning, we investigate an intelligent thermal control emitter based on a multilayer membrane formed by the phase change material vanadium dioxide, metal material Ag, and dielectric materials Ge and ZnS. By incorporating the thermochromic material vanadium dioxide, the structure exhibits a high emissivity of εH = 0.85 in the range of 3–13 μm wavelength when in the high temperature metallic state, enabling efficient heat radiation. In the low temperature dielectric state, the structure only has a low emission capacity of εL = 0.07, reducing energy loss. Our results demonstrate that the structure achieves excellent emission regulation ability (Δε = 0.78) through the thermal radiation modulation from high to low temperature, maintaining effective thermal control. Furthermore, the thermal control emitter exhibits selective emission of peak wavelength due to destructive interference and shows a certain independence on polarization and incidence angle. Additionally, the integration of structural color adjustment capability enhances the visual aesthetics of the human experience. The proposed colored intelligent thermal control structure has significant potential for development in aesthetic items such as colored architecture and energy-efficient materials.

Study of Thermal Instability in Magneto-Convection Nanoliquid Confined within Hele-Shaw Cell Under Three Types of Thermal/Gravity Modulation

In the present paper, we investigate a thermal instability of magneto-convection in an electrically conducting nanoliquid confined within Hele-Shaw cell, subjected to an applied time-periodic boundary thermal (ATBT) or gravitational modulation (ATGM), and surrounded by a constant vertical magnetic field. A steady portion and a time-dependent oscillatory portion constitute the temperature gradient seen between liquid layer’s walls in the context of ATBT. In this scenario, both walls’ temperatures are modulated. The liquid layer oscillation can be used to realise the externally applied time periodic component of the gravity field that is present in the ATGM problem. The perturbation is described in terms of the power series of the assumed-small convective amplitude. The impact of modulations on heat/mass transfer are examined utilising Ginzburg-Landau (GBL) approach. The impact of different parameters on the transportation of mass and heat is also explored. Additionally, we observe that gravitational modulation is very much effective than thermal modulation. Lewis-number, modified-diffusivity ratio and concentration Rayleigh-number increase heat and mass transport in the system.

On-chip spiking neural networks based on add-drop ring microresonators and electrically reconfigurable phase-change material photonic switches

We propose and numerically demonstrate a photonic computing primitive designed for integrated spiking neural networks (SNNs) based on add-drop ring microresonators (ADRMRs) and electrically reconfigurable phase-change material (PCM) photonic switches. In this neuromorphic system, the passive silicon-based ADRMR, equipped with a power-tunable auxiliary light, effectively demonstrates nonlinearity-induced dual neural dynamics encompassing spiking response and synaptic plasticity that can generate single-wavelength optical neural spikes with synaptic weight. By cascading these ADRMRs with different resonant wavelengths, weighted multiple-wavelength spikes can be feasibly output from the ADRMR-based hardware arrays when external wavelength-addressable optical pulses are injected; subsequently, the cumulative power of these weighted output spikes is utilized to ascertain the activation status of the reconfigurable PCM photonic switches. Moreover, the reconfigurable mechanism driving the interconversion of the PCMs between the resonant-bonded crystalline states and the covalent-bonded amorphous states is achieved through precise thermal modulation. Drawing from the thermal properties, an innovative thermodynamic leaky integrate-and-firing (TLIF) neuron system is proposed. With the TLIF neuron system as the fundamental unit, a fully connected SNN is constructed to complete a classic deep learning task: the recognition of handwritten digit patterns. The simulation results reveal that the exemplary SNN can effectively recognize 10 numbers directly in the optical domain by employing the surrogate gradient algorithm. The theoretical verification of our architecture paves a whole new path for integrated photonic SNNs, with the potential to advance the field of neuromorphic photonic systems and enable more efficient spiking information processing.

Photo-thermo-optical modulation of Raman scattering from Mie-resonant silicon nanostructures

Abstract Raman scattering is sensitive to local temperature and thus offers a convenient tool for non-contact and non-destructive optical thermometry at the nanoscale. In turn, all-dielectric nanostructures, such as silicon particles, exhibit strongly enhanced photothermal heating due to Mie resonances, which leads to the strong modulation of elastic Rayleigh scattering intensity through subsequent thermo-optical effects. However, the influence of the complex photo-thermo-optical effect on inelastic Raman scattering has yet to be explored for resonant dielectric nanostructures. In this work, we experimentally demonstrate that the strong photo-thermo-optical interaction results in the nonlinear dependence of the Raman scattering signal intensity from a crystalline silicon nanoparticle via the thermal reconfiguration of the resonant response. Our results reveal a crucial role of the Mie resonance spectral sensitivity to temperature, which modifies not only the conversion of the incident light into heat but also Raman scattering efficiency. The developed comprehensive model provides the mechanism for thermal modulation of Raman scattering, shedding light on the photon–phonon interaction physics of resonant material, which is essential for the validation of Raman nanothermometry in resonant silicon structures under a strong laser field.

Thermal and electrical switchable wide-angle multi-band terahertz absorber.

Multi-band terahertz (THz) absorbers have recently gained attention due to their favorable application prospects in communication, imaging, detection, and other fields. However, many multi-band THz absorbers are tuned by a single method, which limits their tuning effect. To address this issue, we propose a multi-band THz absorber that can be co-modulated by thermal and electrical methods. Our proposed absorber uses vanadium dioxide (VO2) to achieve this co-modulation. When VO2 is insulating, the frequency of the absorbing peaks originating from the lateral Fabry-Pérot resonance mode can be changed by adjusting the VO2 width. When VO2 is a conductor, the quality factor of the absorbing peak based on the inductor-capacitor resonance mode can be tuned by adjusting the width of VO2. By varying the top dielectric layer thickness, the frequency of the absorbing peaks can be tuned over a wide range. For devices with two or three layers of graphene nanoribbons-dielectric stacks, a modulation effect similar to that of varying dielectric layer thickness in a single-layer graphene device can be achieved simply by applying a 1 eV Fermi energy to graphene nanoribbons in different layers. By combining thermal and electrical modulation, the two or three-layer stacked device can be dynamically switched between four or six absorbing states, and a wider range of dynamic peak frequency modulation can be realized. Furthermore, the performance of the absorber does not deteriorate significantly at an incident angle of up to 70°. Our proposed thermal-electrical switchable wide-angle multi-band THz absorber provides a reference for the design, fabrication, and application of high-performance THz absorbers in different fields.

Electrically regulated thermal conductivity of aramid polymer systems

Aramid polymers, renowned for their electronic insulation and thermal conductive properties, are widely adopted as thermal management materials in power electronics. However, the thermal conductivity of aramid polymers under electric field has not been thoroughly understood. In this study, we investigated the thermal conductivity of amorphous and aligned aramid polymer systems under electrical field utilizing equilibrium molecular dynamics simulations. Simulation results showed that the alignment of polymer chain can significantly enhance the thermal conductivity of aramid polymer systems, achieving up to 10.13 W/m-K. Moreover, polarization of aligned aramid polymer was observed when the applied electric field exceeded 14 V/nm. Interestingly, the thermal conductivity of aligned aramid polymer was selectively modulated by the applied electric field. To unravel the underlying phonon mechanism, the molecular orientation of polymer chains and phonon spectral information were analyzed. Our study provides guidance into understanding thermal transport mechanism and thermal conductivity modulation in polymers.

Metasurface with all-optical tunability for spatially-resolved and multilevel thermal radiation

Abstract Manipulating the thermal emission in the infrared (IR) range significantly impacts both fundamental scientific research and various technological applications, including IR thermal camouflage, information encryption, and radiative cooling. While prior research has put forth numerous materials and structures for these objectives, the significant challenge lies in attaining spatially resolved and dynamically multilevel control over their thermal emissions. In this study, a one-step ultrafast laser writing technique is experimentally demonstrated to achieve position-selective control over thermal emission based on the phase-change material Ge2Sb2Te5 (GST). Ultrafast laser writing technique enables direct fabrication and manipulation of laser-induced crystalline micro/nano-structures on GST films. Thermal emission can be precisely controlled by adjusting the pulse energy of the ultrafast laser, achieving a high thermal emissivity modulation precision of 0.0014. By controlling thermal emission, the ultrafast laser writing technique enables multilevel patterned processing. This provides a promising approach for multilevel IR thermal camouflage, which is demonstrated with emissivity-modulated GST emitters. Remarkably, ultrafast laser-induced crystalline micro/nano-structures display geometric grating features, resulting in a diffraction-based structural color effect. This study demonstrates the effective use of laser-printed patterns for storing information in both visible and infrared spectrum.

How much of the energy in the electrochromic energy storage window can be reused?

Electrochromic energy storage technology that can store energy electrochemically while controlling the optical transmittance, could be mainly used in the development of next-generation smart window systems for net-zero energy buildings. The resultant apparatus can first implement indoor optical and thermal modulation, then their involved residual electric energy would be reused to power small electronic products. However, there has been confusion as to how much of the electric energy can be used for secondary purposes. Herein, a hyperbranched polyamide with dual redox centra of triphenylamine and pentaaniline was synthesized with good processability and multi-band absorption. Coupled with a zinc frame electrode, an electrochromic energy storage window (EESW) was manufactured, which simultaneously exhibited approving electrochromic performance (high optical contrast of >48 % and good thermal insulation), as well as ideal zinc ions energy storage properties (wide voltage window of 2.4 V and large capacitance of 71.06 mF cm−2). Furthermore, the spectrochronoamperometry was first coupled with rate performance to investigate its energy reused properties. As implementing electrochromism upon 2.4 V for 50 s, the engaged EESW possessed an energy density of 20.21 μWh cm−2, due to the nonoptimal constant-voltage charging mode. After 1-hour transmittance maintenance without any applied voltage, an 80 % energy density of 16.54 μWh cm−2 was determined, which should be considered available electric energy that can be reused.

Effect of van der Waals homogeneous interface on lattice thermal conductivity of Janus WSSe bilayer

Vertically stacked 2D materials have provided an unprecedented platform to identify various physical properties and discover novel interfacial emergent phenomena. In this study, the lattice thermal conductivity of Janus WSSe bilayer, involving diverse interfacial stacking configurations, has been clarified by solving the phonon Boltzmann transport equation based on first-principles calculations. The effect of homogeneously stacking on thermal conductivity and potential modulation approaches has also been revealed for Janus WSSe. Our results indicate that the thermal transport in Janus WSSe bilayer can be suppressed by van der Waals interface, and depends on both the stacking patterns and interfacial compositions (S-S, Se-Se and Se-S interfaces). Moreover, the interface effect can be further modulated by an applied vertical pressure. A further reduction in thermal conductivity can be achieved for Janus WSSe bilayer under vertical pressure, implying great potential for efficient thermal management and sensing applications.

Flexible Organic Chiral Crystals with Thermal and Excitation Modulation of the Emission for Information Transmission, Writing, and Storage

AbstractOrganic single crystals quickly emerge as dense yet light and nearly defect‐free media for emissive elements. Integration of functionalities and control over the emissive properties is currently being explored for a wide range of these materials to benchmark their performance against organic emissive materials diluted in powders or films. Here, we report mechanically flexible emissive chiral organic crystals capable of an unprecedented combination of fast, reversible, and low‐fatigue responses. UV‐excited single crystals of both enantiomers of the material, 4‐chloro‐2‐(((1‐phenylidene)imino)methyl)phenol, exhibit a drastic yet reversible change in the emission color from green to orange‐yellow within a second and can be cycled at least 2000 times. The photoresponse was found to depend strongly on the excitation intensity and temperature. Combining chirality, mechanical compliance, rapid emission switching, multiple responses, and writability by UV light, this material provides a unique and versatile platform for developing organic crystal‐based materials for on‐demand signal transfer, information storage, and cryptography.