The electrical efficiency of the photovoltaic (PV) panels diminishes with rising cell temperatures, a key challenge in PV performance. While various passive cooling methods exist, there is a need for simple, integrated, and effective thermal management solutions. This study investigates the use of a silicon- based thermal isolator as a novel backsheet material to address this gap. A 0.25 mm Sil-Pad 400 sheet (Henkel) with a thermal conductivity of 0.9 W/m.K was laminated onto solar cells, replacing the standard tedlar layer. The performance of the modified panel was evaluated against an identical reference panel through a single-day, side-by-side comparative test. This protocol, employing synchronized measurements of electrical output and surface temperature from 11:00 to 14:00, ensured that both panels were subjected to identical environmental conditions, thereby normalizing the effect of solar irradiance fluctuations. Results confirmed the superior thermal regulation of the silicon isolator panel, which exhibited average temperature reduction of 4 °C on the front surface, and 2 °C on the back surface, yielding a combined average reduction of 3 °C. This effective cooling translated directly into a significant 13% average increase in power output. These findings demonstrate that silicon-based isolators are a highly promising solution for enhancing PV efficiency and energy yield, offering a practical and scalable approach for improving the performance of real-world solar installations.

This paper reports the first microscale gas chromatography (μGC) system in which all fluidic components are monolithically integrated into a single 15 × 15 mm2 chip, including three Knudsen pumps, a preconcentrator, a separation column, and a capacitive detector. Knudsen pumps utilize thermal transpiration along narrow channels to induce gas flow, providing a compact, motionless solution that enables monolithic integration with high reliability and a long operational lifetime. The flow switching within the system is provided by a unique arrangement of multiple Knudsen pumps that eliminates the need for valves. To realize monolithic integration, the preconcentrator, separation column, and detector are arranged in a planar layout and are designed to be microfabricated using a common fabrication process. Methods to provide heat dissipation and thermal isolation are incorporated. In the experimental evaluation, the fabricated μGC system was operated to analyze the headspace of chemical mixtures, including alkenes, glycol ethers, aromatics, and mercaptans. The results showed a quantification accuracy of ±8.5% for the individual species within the mixtures, which is suitable for specific process monitoring applications in the chemical industry where concentrations of select target species and byproducts must be assessed continuously. The monolithic integration of gas pumps into a μGC system has not been previously reported and is an important step toward further miniaturization of μGC systems.

Cooling materials with light has been a frontier challenge in physics. While Doppler cooling is the most well-known optical cooling method, it is not applicable to solids. Instead, Anti-Stokes (AS) cooling, which utilizes Anti-Stokes photoluminescence (ASPL), has been proposed. ASPL refers to photoluminescence (PL) in which the emission energy exceeds the excitation energy. If the external PL quantum efficiency reaches 100%, the material loses net energy through optical absorption followed by ASPL, resulting in optical cooling. This mechanism fundamentally differs from conventional solid-state cooling based on thermal conduction, as it does not require physical contact to reduce temperature. To date, AS cooling studies have primarily focused on crystals doped with rare-earth ions, which have demonstrated successful AS cooling down to 90 K [1]. However, these systems suffer from weak photoabsorption and intrinsic low-temperature limits.Semiconductors, which exhibit strong optical absorption, are promising candidates for achieving lower temperatures and higher cooling efficiencies. However, AS cooling requires near-unity PL quantum efficiency, which presents a significant challenge for semiconductor systems. In this context, semiconductor quantum dots (QDs) are particularly promising. For optical cooling, we propose a novel QD structure, “dot-in-crystal” perovskites, in which halide perovskite CsPbBr3 QDs are embedded in a transparent Cs4PbBr6 host crystal [2,3]. This structure, hereafter referred to as CsPbBr3/Cs4PbBr6, offers both excellent optical properties and improved photostability. In addition, halide perovskites possess strong electron–phonon coupling [4,5], which enables phonon-assisted photoabsorption and makes them suitable for efficient ASPL. In fact, strong ASPL has been observed in halide perovskites [2,3,5].We first investigated the ASPL characteristics of CsPbBr3/Cs4PbBr6. The PL spectrum remains unchanged regardless of the excitation photon energy. Under below-bandgap excitation, phonon-assisted photoabsorption occurs, enabling ASPL. From detailed analysis of the PL excitation spectra, we demonstrated that optical cooling is possible if the PL quantum efficiency exceeds 97% [3]. Since near-unity PL quantum efficiency has been reported for CsPbBr3/Cs4PbBr6, this strongly supports the feasibility of optical cooling in this material.Although achieving the required PL efficiency is feasible, maximizing the cooling power faces another challenge. While stronger photoexcitation might, intuitively, seem effective, high-density excitation in semiconductors gives rise to nonradiative Auger recombination, which reduces PL efficiency. As a result, the cooling gain cannot increase indefinitely and therefore has an upper limit. Moreover, due to strong quantum confinement, Auger recombination is more prominent in QDs. We investigated this effect in CsPbBr3/Cs4PbBr6 using time-resolved PL spectroscopy [3]. From the excitation-intensity-dependent PL dynamics, we extracted the lifetimes of excitons, trions, and biexcitons, which reflect the influence of nonradiative Auger recombination. Based on these results, we estimated the upper limit of the cooling gain to be approximately 2 fW per QD at the optimized excitation intensity. Combining these results with the Stefan–Boltzmann law, we estimated that the lowest achievable temperature of CsPbBr3/Cs4PbBr6 under ideal thermal isolation is approximately 10 K below room temperature [3].Building on the above insights, we carefully performed cooling experiments on CsPbBr3/Cs4PbBr6 under optimized excitation conditions [3]. Since non-contact temperature measurement is essential, we employed a newly developed PL thermometry technique, which estimates the temperature from the high-energy tail of the PL spectrum. This method provides reliable temperature estimates with an accuracy of about 1 K. We used CsPbBr3/Cs4PbBr6 microparticles placed on a mica substrate inside a vacuum chamber, and selected a highly luminescent particle. We observed a temperature reduction of approximately 9 K under continuous-wave photoexcitation. This provides the first clear evidence of optical cooling of perovskite QDs. Furthermore, by tuning the excitation intensity, we demonstrated a transition from cooling to heating, in good agreement with the model that incorporates Auger recombination.In the presentation, we will discuss the ASPL mechanism in halide perovskites, which arises from phonon-assisted photoabsorption. We will also highlight the current limitations of semiconductor optical cooling and explore possible strategies to overcome these challenges, along with future prospects for this emerging technology.Part of this work was supported by the Asahi Glass Foundation and JST-CREST (Grant No. JPMJCR21B4).

ABSTRACT This study presents the design and development of a novel lightweight bicycle brake disc that offers significant improvements in weight reduction, thermal performance, and aesthetic customization compared to conventional models. Traditional bicycle brake discs, typically made entirely of chromium-molybdenum steel, are relatively heavy and susceptible to excessive heat buildup during prolonged braking. The newly designed brake disc features a composite structure, incorporating a chromium-molybdenum steel outer frame for mechanical strength and a lightweight aluminum alloy core to reduce overall weight while maintaining structural integrity significantly. The brake disc design enhances aesthetics through an anodized aluminum alloy center frame, allowing for vibrant color customization tailored to fleet and brand preferences. More importantly, the riveted joint structure between the steel outer frame and the aluminum core acts as a thermal insulation, increasing thermal resistance and preventing excessive heat transfer to the hub. This design effectively reduces thermal deformation risk, improving braking reliability and rider safety. This study investigates the thermal properties and fatigue crack growth behavior of a proposed composite brake disc through a combination of experimental testing and numerical simulations. A comparison between the traditional brake disc (Model A) and the novel composite brake discs (Models B, C, and D) reveals that Model D demonstrates the most effective thermal isolation. In addition, structural evaluations indicate that Model D significantly outperforms Model A in terms of deformation, stress, fatigue life, damage, and safety factors. Model D demonstrates a significantly higher maximum fatigue life of 108 cycles, which is 100 times greater than that of Model A. These findings provide valuable insights for optimizing performance, enhancing safety, and improving the user experience in modern bicycle braking systems.

We demonstrate refractive index trimming of visible-light silicon nitride (SiN) waveguides using suspended heater structures. The thermal isolation of the suspended heaters enabled a semi-uniform temperature distribution with estimated temperatures of ∼350°C in the waveguides without reaching potentially damaging temperatures in the titanium nitride resistive heaters. The thermal isolation also enabled trimming temperatures to be reached with a moderate power dissipation of 30 to 40 mW. At a wavelength of 561 nm, modal effective index changes up to -8.3 × 10-3 were observed following thermal trimming, and the index changes were stable over an observation period of 97 days. The devices were fabricated as part of our visible-light integrated photonics platform on 200-mm diameter silicon wafers. The suspended heaters also functioned as efficient thermo-optic phase shifters with power dissipation for a π phase shift of about 1.2 - 1.8 mW. The trimming method was applied to set the bias points of thermo-optic Mach-Zehnder interferometer switches to reduce the bias power of five devices from 0.29 - 2.32 mW to 0.1 - 0.16 mW. Thermal trimming at a wavelength of 445 nm was also demonstrated. Through material analysis before and after thermal treatment, we hypothesize that index trimming of the silica (SiO2) waveguide cladding may be a potential underlying mechanism. Additionally, via extrapolations of the measured trimming data, we estimate the thermal aging behavior of the SiN waveguides in the suspended heaters at lower (125 - 250°C) operating temperatures.

Infrared (IR) thermal sensors on CMOS-SOI-MEMS platforms enable scalable, low-cost thermal imaging but require optimized optical, thermal, and mechanical performance. This paper presents a multiphysics modeling framework to study the integration of Metasurface absorbers into a Thermal CMOS-SOI-MEMS IR sensor. Using finite-difference time-domain (FDTD) simulations, we demonstrate near-unity absorption at targeted wavelengths (e.g., 4.26 µm for CO2 sensing, 10 µm for thermal imaging) compared to conventional absorbers. The absorbed power, calculated from blackbody irradiance, drives thermal finite element analysis (FEA), confirming high thermal isolation and maximized temperature rise (ΔT) while quantifying the thermal time constant’s sensitivity to Metasurface mass. An analytical RC circuit model, validated against 3D FEA, accurately captures thermal dynamics for rapid design iterations. Mechanical modal and harmonic analyses verify structural integrity, with natural frequencies above 20 kHz, ensuring resilience against mechanical resonances and environmental vibrations. This holistic framework quantifies trade-offs between optical efficiency, thermal responsivity, and mechanical stability, providing a predictive tool for designing high-performance, uncooled IR sensors compatible with CMOS processes.

This paper presents the experimental implementation and validation of the two-chamber method presented in Part I for the high-precision determination of the temperature coefficient of resistance (TCR) of current shunts. The two-chamber approach enables improved thermal isolation and independent temperature control of the reference and test shunts, which significantly reduces the measurement uncertainty. In this part, the complete experimental setup is described, including the thermoelectric temperature control, the current generation and the data acquisition system with synchronized high-resolution digital multimeters (DMMs). The experimental measurements were carried out for different resistance ratios ranging from 0.1 to 10. The results confirm the theoretical predictions and the uncertainty analysis from Part I. The influences of the stability of the current source, the temperature uniformity and the synchronization accuracy on the measurement results are evaluated. The two-chamber method shows high repeatability, ease of use and suitability for laboratory and interlaboratory tests, and thus represents a robust alternative to classical TCR determination methods.

Self-heating effects are a growing reliability challenge in vertically stacked Complementary Field-Effect Transistors (C-FETs) due to structural thermal isolation introduced by vertical integration—unlike in conventional lateral CMOS. To address this, we investigate Buried Power Rail (BPR) architecture in the Middle-of-Line (MOL) region, replacing conventional front-side power delivery networks (FS-PDNs) to enhance vertical thermal conduction in nanoscale (∼3 nm node) C-FETs. 3D electro-thermal technology computer-aided design (TCAD) simulations were conducted using a comprehensive thermal model that incorporates size-dependent conductivity, interfacial thermal resistance, and package-aware boundary conditions. The BPR configuration reduced peak lattice temperature by up to 3.7% and thermal resistance by 7.5% compared to FS-PDN while maintaining electrical performance even under middle dielectric isolation variation. An electro-thermal figure-of-merit, combining delay and temperature rise, improved by 3.1% despite modest resistance–capacitance delay trade-offs, demonstrating superior thermal robustness. These results provide practical design insights for enabling reliable nanoscale C-FET operation through MOL-level thermal path engineering.

This manuscript is aimed at analyzing how operating factors may affect the durability of thermal insulation in building partitions located underground. It examines the durability of inverted insulation systems where thermal insulation is installed above the waterproofing layer and used in residential foundation slabs. The article demonstrates that, despite their popularity due to cost efficiency, the long-term success of these systems depends on thorough investigations of thermal isolation, especially considering different climate conditions. The analysis was based on an extensive literature review (2016–2024), supplemented with laboratory test results on extruded (XPS) and expanded (EPS) polystyrene boards. Additional tests examined the water penetration mechanism into insulation layers that are in direct contact with groundwater, revealing that cyclic freezing and thawing significantly increase moisture levels. The findings highlight the need for updated region-specific guidelines for the underground insulation in Central and Eastern Europe.

Abstract The high thermal conductivity of silicon has limited its use in thermal radiative devices where minimizing conductive cooling is a priority. Recent advancements in phononic MEMS technology enable a significant reduction in the thermal conductivity of electrically conductive nanowires, achieving extreme thermal isolation for semiconductor applications. This technology can lower thermal conductivity to a nanoWatt/K level approaching the dielectric limit. The nanowires are configured as phononic crystals which increase Bragg scattering of phonons, providing an extreme level of thermal isolation for application devices.
This paper reports for the first time a highly efficient silicon broadband infrared light source based on phononic MEMS technology with emission in the near infrared (NIR) - midwave infrared (MWIR) – longwave infrared (LWIR) wavelength range. The thermal light source is fabricated from a starting silicon-on-insulator (SOI) wafer wherein a heated micro-platform and supporting nanowires are released from the surrounding substrate by removing the underlying SiO2 layer. The nanowires are configured with phononic crystal structure.
The infrared source is an array of silicon pixels packaged within a vacuum cavity providing broadband infrared NIR-MWIR-LWIR radiation from micro-platforms. The device is called a light-emitting platform (LEP), which differentiates it from a narrowband LED emitter.
LEP pixel radiative power efficiency within the vacuum cavity is over 90% with micro-platform temperature as high as 800 ˚C for silicon. The LEP efficiency compares with an Edison incandescent lightbulb at less than 10% for RGB light and 2.5% for uncooled LEDs emitting in the 2.3 µm wavelength range. Applications include MWIR floodlights, spotlights, vehicle headlights, biomedical stimulators, instrumentation light sources, etc.

We present low-loss (<1.5%) and power-efficient Mach-Zehnder interferometers (MZIs) on thin-film lithium niobate. To accurately measure small MZI losses, we develop a self-calibrated method using tunable Sagnac loop reflectors (SLRs) to build cavities. Fabry-Pérot cavities constructed from these SLRs achieve an intrinsic quality factor of 2×106. By implementing thermal isolation trenches, we also demonstrate a >10× reduction in power consumption for thermo-optic phase shifters, achieving a Pπ of 2.5 mW. These components are crucial for scaling up complex photonic integrated circuits.

Silicon photonic devices are fundamental to high-density wavelength-division multiplexed (DWDM) optical links and photonic switching networks, such as resonant modulators and Mach-Zehnder interferometers (MZIs), and are highly sensitive to fabrication variations and operational temperature swings. However, thermal tuning to compensate for fabrication and operational temperature variations can result in prohibitive power consumption, challenging the scalability of energy-efficient photonic integrated circuits (PICs). In this work, we develop and demonstrate a wafer-scale thermal undercut process in a 300 mm complementary metal oxide semiconductor (CMOS) foundry that dramatically improves the thermal isolation of thermo-optic devices by selectively removing substrate material beneath the waveguides and resonators. This approach significantly reduces the power required for thermal tuning across multiple device architectures, achieving almost a 5times improvement in tuning efficiency in a state-of-the-art 4.5 upmum radius microdisk modulator and a 40times improvement in efficiency for a MZI phase shifter. To the best of the authors’ knowledge, we demonstrate the first wafer-scale comparison of non-undercut and undercut silicon photonic devices using comprehensive wafer-scale measurements across 64 reticles of a 300 mm silicon-on-insulator (SOI) wafer. Further, we demonstrate a comprehensive wafer-scale analysis of the influence of undercut trench opening geometry on device tuning efficiency. Notably, we observe highly uniform performance across the full 300 mm wafer for multiple device types, emphasizing that our process can be scaled to large-scale photonic circuits with high yield. These results open new opportunities for large-scale integrated photonic circuits using thermo-optic devices, paving the way for scalable, low-power silicon photonic systems.

Ceramic insert enabled build plate thermal isolation for enhanced microstructure and residual stress mitigation in laser-based powder bed fusion of metals

Optical switches are crucial components in integrated optics, with broad applications in data communications, sensing, and computing. We experimentally demonstrate an ultra-efficient silicon thermo-optic Mach-Zehnder switch based on waveguide superlattices with artificial gauge field. A sinusoidal modulation profile is typically applied to a binary waveguide array to achieve low-crosstalk and broadband light transmission. This design achieves the lowest power consumption of 1.21 mW without extra thermal isolation. Geometric design optimization, central to this demonstration, can be utilized to develop compact and high-efficiency devices for large-scale photonic integrated circuits. This approach paves the way for significantly reducing power consumption while maintaining scalability.

This work presents an on-field noise analysis during the class breaks in Greek school units (a high school and a senior high school) based on the design and deployment of low-cost IoT sensor nodes and IoT platforms. The course breaks form 20% of a regular school day, during which intense mobility and high noise levels usually evolve. Indoor noise levels, along with environmental conditions, have been measured through a wireless network that comprises IoT nodes that integrate humidity, temperature, and acoustic level sensors. PM10 and PM2.5 values have also been acquired through data sensors located nearby the school complex. School buildings that have been recently renovated for minimizing their energy footprint and CO2 emissions have been selected in comparison with similar works in academia. The data are collected, shipped, and stored into a time-series database in cloud facilities where an IoT platform has been developed for processing and analysis purposes. The findings show that low-cost sensors can efficiently monitor noise levels after proper adjustments. Additionally, the statistical evaluation of the received sensor measurements has indicated that ubiquitous high noise levels during the course breaks potentially affect teachers’ leisure time, despite the thermal isolation of the facilities. Within this context, we prove that the proposed IoT Sensor Network could form a tool to essentially monitor school infrastructures and thus to prompt for improvements regarding the building facilities. Several guides to further mitigate noise and achieve high-quality levels in learning institutes are also described.

Triboelectric nanogenerator (TENG) is burgeoning as both a promising energy harvester and a self-powered sensor. However, the mechanical strength, flexibility, and overall functionality of TENGs are irreversibly impacted by the chemical and physical changes of the polymer at high temperatures. Here, core-shell structured expanded-perlite@graphene particles are conveniently synthesized by high-temperature carbonization reaction, which are then introduced into polydimethylsiloxane (PDMS) to form a robust composite foam (EPGP) with excellent thermal insulation and flame retardancy. The thermal resistance of the EPGP (0.0145m2KW-1) is ≈2.1 times that of PDMS, while reducing heat/smoke release rates by 84%/44% and total heat/smoke release by 44%/76%.For energy conversion and mechanical sensing, the EPGP-based TENG shows 186V open-circuit voltage and 0.3µAcm-2 short-circuit current at room temperature, which is 2.7 and 3.2 times higher than the PDMS-based TENG. Even at 200°C, the output also remains stable at 106V and 0.16µAcm-2. The as-designed TENGs in monitoring the engine's malfunction/compressor operation at high-temperatures and extended periods are realized by detecting abnormal vibrations. The instant monitoring of the engine status shows graphically the performance degradation, thus functioning as a new indicator that informs fault while driving, while advancing thermal-insulation composites for TENG-based microelectronics in extreme environments.

— Design and optimization of a heat-resistant pallet for an Autonomous Mobile Robot (AMR) intended for industrial material handling. The pallet is engineered to withstand loads up to 500 kg and surface temperatures reaching 200°C, addressing a common industrial challenge where heat transfer from hot materials can damage AMR components. The solution involves a multi-layered pallet structure, combining high-temperature insulation materials such as ceramic composites, mica sheets, and GFRP, designed to resist heat while maintaining structural integrity. A detailed CAD model of the pallet was developed in Solid Works, and thermal and structural analyses were conducted using simulation tools FUSION 360 to validate material performance under high load and temperature conditions. The optimized design achieves a bottom surface temperature reduction of up to 18.7% (from 52.84°C to 42.79°C) and an increase in thermal gradient of over 115% (from 4.997°C/mm to 10.809°C/mm), demonstrating improved thermal isolation with insulation materials.

Nonmetal elements have remarkable potential in modulating the metal-insulator transition behavior of VO2, but little is known about their impact on thermochromic performance. Here, phosphorus (P) is successfully doped into VO2 by the precursor decomposition diffusion. XPS spectra, together with DFT calculations, demonstrate V-substitutional doping (Pv). The onset transition temperature of P-doped VO2 decreases from 62.8 to 50.2 °C. Theoretical calculations reveal that PV interferes with strong V-V interactions, decreasing the d orbital occupancy. However, the worse crystallinity leads to severe NIR modulation degradation even though luminance transmittance is enhanced by 6%. P-gradient films are developed to effectively address the weakening of NIR modulation caused by element doping. The film with decreased P concentration has an optimal solar-energy modulation ability (ΔTsol) of 11.8%, a 36% enhancement over the undoped one (8.7%). Attractively, a P-gradient VO2 smart window shows outstanding temperature response NIR modulation and thermal isolation performance; the indoor temperature of its model house decreased by 6.8 °C compared to the blank window after 25 min irradiation. This work provides a simple and effective idea to improve the element doping-induced NIR modulation degradation.

Non-equilibrium molecular dynamics (NEMD) simulations of fluid flow have highlighted the peculiarities of nanoscale flows compared to classical fluid mechanics; in particular, boundary conditions can deviate from the no-slip behavior at macroscopic scales. For fluid flow in slit-shaped nanopores, we demonstrate that surface morphology provides an efficient control on the slip length, which approaches zero when matching the molecular structures of the pore wall and the fluid. Using boundary-driven, energy-conserving NEMD simulations with a pump-like driving mechanism, we examine two types of pore walls-mimicking a crystalline and an amorphous material-that exhibit markedly different surface resistances to flow. The resulting flow velocity profiles are consistent with Poiseuille theory for incompressible, Newtonian fluids when adjusted for surface slip. For the two pores, we observe partial slip and no-slip behavior, respectively. The hydrodynamic permeability corroborates that the simulated flows are in the Darcy regime. However, the confinement of the fluid gives rise to an effective viscosity below its bulk value; wide pores exhibit a crossover between boundary and bulk-like flows. In addition, the thermal isolation of the flow causes a linear increase in fluid temperature along the flow, which we relate to strong viscous dissipation and heat convection, utilizing conservation laws of fluid mechanics. Noting that the investigated fluid model does not form droplets, our findings challenge the universality of previously reported correlations between slippage, solvophobicity, and a depletion zone. Furthermore, they underscore the need for molecular-scale modeling to accurately capture the fluid dynamics near boundaries and in nanoporous materials, where macroscopic models may not be applicable.

A tip-tilt-piston 3 × 3 electrothermal micromirror array (MMA) integrated with temperature field-based position sensors is designed and fabricated in this work. The size of the individual octagonal mirror plates is as large as 1.6 mm × 1.6 mm. Thermal isolation structures are embedded to reduce the thermal coupling among the micromirror units. Results show that each micromirror unit has a piston scan range of 218 μm and a tip-tilt optical scan angle of 21° at only 5 Vdc. The micromirrors also exhibit good dynamic performance with a rise time of 51.2 ms and a fall time of 53.6 ms. Moreover, the on-chip position sensors are proven to be capable for covering the full-range movement of the mirror plate, with the measured sensitivities of 1.5 mV/μm and 8.8 mV/° in piston sensing and tip-tilt sensing, respectively. Furthermore, the thermal crosstalk in an operating MMA has been experimentally studied. The measured results are promising thanks to the embedded thermal isolation structures.