Search Results (37)

This study evaluated the performance of thermochromic windows as dynamic envelopes for smart greenhouses, focusing on the light environment and cooling load under peak summer conditions. Four covering materials, glass, Low-E glass, polycarbonate, and thermochromic windows, were compared using EnergyPlus (v9.2.0) simulation for an 8-span greenhouse with a floor area of 1008 m² in Gwangju, South Korea, on a representative summer day of 21 July. Thermochromic properties were modeled with temperature-dependent SHGC variations from 0.521 at 25 °C to 0.425 at 85 °C. Results showed that thermochromic windows reduced noon illuminance by 75% compared to conventional glass, from 26,482 lux to 6628 lux, while maintaining adequate light levels above the compensation point for tomato and paprika cultivation. Simultaneously, peak cooling load decreased by 13.1%, from 537,929 W to 467,477 W, outperforming Low-E glass at 9.2% and polycarbonate at 7.0%. At peak hours of 1:00 p.m., when the glass surface temperature reached 60.5 °C, the thermochromic glazing reduced transmitted solar radiation by 37.8% per unit area compared to conventional glass. This study demonstrates that thermochromic windows effectively balance photosynthetic light provision and cooling energy reduction in smart greenhouses, offering a viable design solution for controlled environment agriculture under extreme summer conditions. Full article

The escalating energy crisis and global warming drive the demand for all-season self-regulating functional textiles. This study presents a Janus smart textile that combines phase change energy storage with active and passive heating modes, electromagnetic interference shielding, and self-cleaning capabilities. The front surface incorporates phase change temperature regulation and thermochromic properties, while the back surface is spray-coated with a transition metal carbide to establish a continuous conductive network. In the low-temperature state, the black surface enhances solar absorption for efficient heating; as the temperature rises, the surface turns white to increase solar reflection and suppress overheating. This mechanism, combined with phase change energy storage, enables the textile to mitigate environmental temperature fluctuations. The MXene layer on the back provides efficient Joule heating and cycling stability under driving voltages of 3 to 5 volts, along with electromagnetic interference shielding dominated by absorption loss. The front hybrid coating further imparts hydrophobic self-cleaning performance. This study offers a strategy for synergistic active and passive thermal management, demonstrating application potential in intelligent outdoor gear and specialized protective outer layers. Full article

Thermochromic materials (TCMs) have attracted increasing attention as passive adaptive materials for solar regulation in buildings because they can reversibly change their optical properties in response to temperature without external energy input. Owing to this temperature-triggered optical modulation, they have been widely investigated for smart windows, temperature indicators, anti-counterfeiting labels, and flexible devices. In recent years, representative systems such as VO₂-based materials, polymers, hydrogels, and organic–inorganic hybrids have shown steady progress, especially in transition-temperature tuning, spectral selectivity, and cycling stability. This review summarizes the main classes of TCMs as well as their color-changing mechanisms, preparation methods, and performance-regulation strategies, with an emphasis on building energy efficiency and passive solar regulation. Typical applications and current bottlenecks are also discussed, including response speed, durability, environmental compatibility, and large-scale manufacturing. Finally, several practical directions for future work are highlighted, particularly low-cost synthesis, multifunctional integration, and application-oriented material design. Full article

Artificial intelligence (AI) is increasingly applied to the design and optimization of solar thermal collectors, particularly in the development of selective absorber coatings. This systematic review analyzes recent advances (2020–2026) in AI-driven modeling, optimization, and sustainability strategies for solar thermal technologies following the PRISMA 2020 methodology. The results indicate that current research is largely dominated by Artificial Neural Networks and metaheuristic algorithms, mainly focused on short-term performance prediction and system-level optimization. However, durability, degradation mechanisms, and life-cycle sustainability metrics remain significantly underrepresented in AI-assisted design frameworks. From a materials perspective, recent studies highlight the emergence of multifunctional absorber surfaces, including thermochromic, self-cleaning, and multilayer coatings, often combined with AI-enabled monitoring and digital twin approaches. In addition, sustainable processing routes such as green sol–gel synthesis and low-temperature deposition show strong potential for reducing environmental impact when integrated with AI-based optimization. Nevertheless, the holistic integration of AI with sustainability metrics at the early design stage remains limited. Future research should therefore focus on hybrid and physics-informed AI frameworks capable of simultaneously addressing performance, durability, economic viability, and environmental impact in solar thermal collector design. Full article

Reversible thermochromic materials change color in response to temperature variations and hold significant potential in smart textiles. Their reversible color-changing property not only offers temperature indication and enhances textile performance but also promotes smart textile development. This is achieved by improving the intelligence, multifunctionality, and environmental adaptability of textiles. This review summarizes the characteristics and recent advancements of reversible thermochromic materials, including leuco dye-based organic systems and other organic, liquid crystal (LC), inorganic, and photonic crystal (PC) types. It emphasizes recent progress in integrating these materials into textiles through techniques such as microencapsulation, printing and dyeing, and fiber fabrication. Furthermore, this review systematically examines applications of reversible thermochromic materials in smart textiles, covering areas such as anti-counterfeiting, temperature-sensitive regulation, and aesthetic enhancement. Current challenges, including limited stability, inadequate wash durability, and low color sensitivity, are also addressed, alongside potential development directions. The aim of this review is to provide a theoretical foundation and technical guidance for designing and developing reversible thermochromic smart textiles. Full article

The development of multifunctional smart packaging materials capable of simultaneously monitoring temperature and suppressing microbial contamination is critical for next-generation food and pharmaceutical safety systems. In this study, we report the design and characterization of a polymeric film integrating a spin crossover (SCO)-based thermochromic sensor with zinc oxide (ZnO) nanoparticles serving as an antimicrobial agent. Beyond the individual functionalities, we demonstrate a synergistic effect between SCO and ZnO components. Notably, the SCO transition of the pristine SCO complex is broadened, and the hysteresis width of the transition is decreased (i.e., from 6 K to 1.5 K, 2 K, and 1.5 K for ZnO loading of 0.5%, 1%, and 2%, respectively), in the polysulfone–SCO–ZnO composites. Migration studies reveal that the co-existence of SCO and ZnO does not disrupt the low release profile of active agents, which remains low across ZnO loadings. The polymeric film exhibited dose-dependent antiproliferative activity against MCF-7 breast cancer cells, with a significant reduction in cell viability observed only at the highest tested concentration, indicating cytotoxic potential. This multifunctional platform represents a promising advancement in smart packaging design, enabling real-time thermal indication combined with the integration of ZnO as a literature-established antimicrobial component, within a non-toxic, and visually transparent system. Collectively, the material’s properties offer promising scalability for both food and pharmaceutical packaging applications where visual clarity, antimicrobial integrity, and temperature monitoring are imperative. Full article

Thermochromic VO₂ crystalline domains have been formed in amorphous nanocolumnar VO_x films by means of a low-temperature oxidation process. The oxidation of an amorphous film with [O]/[V] below 1.9 favors the formation of VO₂, V₃O₇, and V₂O₅ crystalline domains in the material for temperatures as low as 260 °C, while values above 1.9 lead to the sole formation of the V₂O₅ phase. It is found that the absorption of oxygen also causes a relevant film volume expansion that makes pores shrink. Under some specific conditions, low-temperature oxidation causes the near disappearance of the amorphous regions, clearly improving the overall transparency and optimizing the optical and electrical modulation capabilities associated with the presence of crystalline VO₂ domains. The best thermochromic performance was found when the original stoichiometry was [O]/[V] = 1.5 and the oxidation temperature was 280 °C. These conditions yield a relatively transparent coating in the visible range that presents an optical modulation in the near-infrared range of nearly 50% and a drop of electrical resistivity of more than two orders of magnitude, with a transition temperature of 50.3 °C. A tentative model based on the volume expansion experienced by the film upon oxidation is proposed, which links the structural/chemical features of the material and the formation of the crystalline domains at such relatively low temperatures. Full article

Thermochromic smart windows are a promising technology to reduce energy consumption in buildings, particularly in tropical regions where cooling demands are high. Vanadium dioxide (VO₂) is the most studied thermochromic material due to its reversible semiconductor-to-metal transition near 68 °C. Conventional synthesis routes require long reaction times and post-annealing steps. In this work, we report a rapid hydrothermal synthesis of monoclinic VO₂(M) and tungsten-doped VO₂(M) powders obtained within only 6 h at 270 °C, using vanadyl sulfate as precursor and controlled precipitation at pH ≈ 8.5. Differential scanning calorimetry confirmed the reversible transition at 59 °C for the undoped VO₂, with a hysteresis of 18 °C, while tungsten doping reduced the transition temperature by ~17 °C per wt.% of W. X-ray diffraction verified the monoclinic phase with minor traces of VO₂(B), a non-thermochromic polymorph of VO₂, and microstructural analysis revealed crystallite sizes below 35 nm. Electron microscopy and dynamic light scattering confirmed particle sizes suitable for dispersion in polymeric matrices. This approach significantly reduces synthesis time compared to typical hydrothermal methods requiring 20–48 h and avoids further annealing. The resulting powders provide a low-cost and scalable route for fabricating thermochromic coatings with transition temperatures closer to ambient conditions, making them relevant for smart-window applications in tropical climates, where lower transition temperatures are generally regarded as beneficial. Full article

Tungsten-doped vanadium dioxide (W-VO₂) shows semiconductor-to-metal phase transition properties at room temperature, which is an ideal thermo-chromic smart window material. However, low visual transmittance and solar modulation limit its application in building energy saving. In this paper, a W-VO_2−x@AA core-shell nanoparticle is proposed to improve the thermo-chromic performance of W-VO₂. Oxygen vacancies were used to promote the connection of W-VO_2−x nanoparticles with L-ascorbic acid (AA) molecules. Oxygen vacancies were tuned in W-VO₂ nanoparticles by thermal annealing temperatures in vacuum, and W-VO_2−x@AA nanoparticles were synthesized by the hydrothermal method. A smart window was formed by dispersing W-VO_2−x@AA core-shell nanoparticles into PVP evenly and spin-coating them on the surface of glass. The visual transmittance of this smart window reaches up to 67%, and the solar modulation reaches up to 12.1%. This enhanced thermo-chromic performance is related to the electron density enhanced by the AA surface molecular coordination effect through W dopant and oxygen vacancies. This work provides a new strategy to enhance the thermo-chromic performance of W-VO₂ and its application in the building energy-saving field. Full article

Coatings can achieve the property of changing color with temperature variations by adding thermochromic microcapsules, which can bring a variable surface to the substrate. Ultraviolet ray (UV)-cured primers have the advantages of a fast curing rate, low-temperature curing, and low pollution. Thermochromic microcapsules can expand the application range of UV primers. Thermochromic microcapsules were synthesized through an orthogonal test, using crystal violet lactone, bisphenol A, and decanol as the core materials in a 1:4:50 mass ratio, with urea formaldehyde resin as the wall material. The effects of the addition of batches of the urea, the mass ratio of the formaldehyde solution to the urea, the hydrophilic–lipophilic balance (HLB) value of the emulsifier, and core-to-wall mass ratio on microcapsules yields, encapsulation rates, thermochromic color differences (ΔE), and formaldehyde releases during synthesis were investigated. The results were normalized, with the thermochromic ΔE as the primary reference for analysis. The results indicate that the HLB value of the emulsifier was the key factor that affected the microcapsule performance. In a single-factor test, the HLB value was adjusted within the range of 6.00 to 10.00. It was found that when the HLB value was 10.00, the microcapsules exhibited the best comprehensive performance, with a yield of 43.29%, an encapsulation rate of 45%, a thermochromic ΔE of 4.60, and a formaldehyde concentration released of 1.310 mg/L. The 11# microcapsules with the optimal morphology and better comprehensive performance were compared with the best 14# microcapsules. Different amounts of these microcapsules were added to the UV primer to investigate the effects of the 11# and 14# microcapsules on the mechanical and optical properties of the UV primer. The main component of the UV primer was polyurethane acrylic resin, propylene glycol diacrylate, and hexanediol diacrylate. When 14# microcapsules were added to the UV primer at a concentration of 10%, the primer exhibited the best comprehensive performance, with a fracture elongation of 17.44%, a roughness of 0.15 μm, and a visible light transmittance of 83%. Microcapsule technology was used to modify UV primers, endowing them with thermochromic properties and expanding the application range of thermochromic microcapsules. Full article

Reducing energy consumption in buildings is critical to reducing CO₂ emissions and mitigating global warming. Studies have shown that heating and cooling loads account for more than 40% of building energy consumption, and thermochromic glass (TCG) with dynamically adjustable solar transmittance is an excellent way to reduce this load. Although a large number of studies have tested the spectral parameters of TCG in totally transparent and totally turbid states, the impact of dynamic changes in optical properties on the simulation accuracy of building energy consumption has been neglected. In this study, a method is proposed for a hydrogel-type TCG to dynamically test its spectral parameters based on spectrophotometry. The method uses a spectrophotometer and a PID heater to achieve the dynamic optical parameter testing of TCGs at different temperatures. In this paper, the transmission and reflection spectra of the two TCGs at 20~25 °C, 30~35 °C, 40 °C, 45 °C, 50 °C, and 55 °C were obtained, and the regression segmentation functions of visible transmittance and solar transmittance were established. The R² of the function model is 0.99. In addition, the test results show that the thermochromic glass selected in this paper can selectively transmit different wavelengths of light, and its transmission mainly occurs in the visible and near-infrared wavelengths from 320 to 1420 nm, while the transmission rate of other wavelengths is very low. As the temperature increases, the visible, solar, and ultraviolet transmittances decrease at a similar rate. In addition, the higher the temperature acting on the thermochromic (TC) layer, the greater its haze. Full article

This review article delves into the intriguing phenomenon of low-temperature thermochromism, whereby materials change color in response to temperature variations, with a particular focus on its applications in temperature-sensitive fields like medical storage. By closely examining thermochromic materials, this article highlights their potential to offer innovative solutions for monitoring and preserving thermolabile products that require strict temperature control. This leads to a special emphasis on polydiacetylenes (PDAs), a class of conjugated polymers with unique low-temperature thermochromic properties, positioning them as promising candidates for reliable temperature indicators. This article then explores the underlying mechanisms for fine-tuning the thermochromic behavior of PDAs, particularly discussing recent advancements in PDA design, such as structural alterations of monomers to achieve low-temperature thermochromism. These modifications, influenced by factors like side-chain length, hydrogen-bonding interactions, and the use of copolymers, are intended to result in irreversible color transitions at specific low temperatures, which is crucial to maintaining the integrity of thermally sensitive products. Finally, this article discusses the potential applications of PDAs as thermochromic sensors in tissue biobanking, where their ability to provide visual indications of temperature fluctuations could significantly enhance the monitoring and management of biological samples. Full article

The growing use of glass in architecture has driven research into reducing its energy consumption. Thermochromic (TC) glass technology shows promise for enhancing building energy efficiency by regulating solar heat dynamically. Although TC glass helps reduce heat radiation, additional solutions like Low-E or vacuum glass are needed to control heat convection and conduction. Low-E glass, while effective in lowering heat transfer, may increase surface temperature. Thermo-sensitive hydrogels, known for their light-scattering properties at high temperatures, have been explored to complement TC glass. However, their stability at elevated temperatures remains a challenge, especially for applications requiring durability under varying weather conditions. This study proposes enhancing the adhesion between hydrogel and glass by introducing silica–oxygen bonds. As a result, TC glass demonstrates stable performance over 100 cycles within temperature ranges from 85 °C to 30 °C in summer and 40 °C to −20 °C in winter. Furthermore, by incorporating ethylene glycol, the freezing point of TC glass is reduced to −26 °C, rendering it suitable for use in colder regions. The implementation of TC glass effectively addresses the dual requirements of summer shading and winter heating in areas with both cold winters and hot summers, significantly reducing building energy consumption. This study contributes substantially to developing advanced intelligent building materials, paving the way for more sustainable architectural designs. Full article

This study introduces the synthesis and detailed characterization of a novel thermochromic material capable of reversible alterations in its thermotropic transmittance. Through an emulsion polymerization process, this newly developed material is composed of 75–85% octadecyl acrylate and 0–7% allyl methacrylate, demonstrating a pronounced discoloration effect across a narrow yet critical temperature range of 24.5–39 °C. The synthesized powder underwent a battery of tests, including differential scanning calorimetry and thermogravimetric analysis, as well as scanning electron microscopy. These comprehensive evaluations confirmed the material’s exceptional thermal stability, uniform particle size distribution, and strong anchoring properties. Building upon these findings, we advanced the development of thermochromic polyvinyl butyral films and laminated glass products. By utilizing a coextrusion technique, we integrated these films into laminated glass, setting a new benchmark against existing glass technologies. Remarkably, the incorporation of thermochromic PVB films into laminated glass led to a significant reduction in solar irradiance of 20–30%, outperforming traditional double silver low-emissivity glass. This achievement demonstrates the exceptional shading and thermal insulation properties of the material. The research presented herein not only pioneers a valuable methodology for the engineering of smart materials with tunable thermotropic transmittance but also holds the key to unlocking enhanced energy efficiency across a spectrum of applications. The potential impact of this innovation on the realm of sustainable building materials is profound, promising significant strides toward energy conservation and environmental stewardship. Full article

Thermochromic smart windows realize an intelligent response to changes in environmental temperature through reversible physical phase transitions. They complete a real-time adjustment of solar transmittance, create a livable indoor temperature for humans, and reduce the energy consumption of buildings. Nevertheless, conventional materials that are used to prepare thermochromic smart windows face challenges, including fixed transition temperatures, limited solar modulation capabilities, and inadequate mechanical properties. In this study, a novel thermochromic hydrogel was synthesized from 2-hydroxy-3-butoxypropyl hydroxyethyl celluloses (HBPEC) and poly(N-isopropylacrylamide) (PNIPAM) by using a simple one-step low-temperature polymerization method. The HBPEC/PNIPAM hydrogel demonstrates a wide response temperature (24.1–33.2 °C), high light transmittance (T_lum = 87.5%), excellent solar modulation (ΔT_sol = 71.2%), and robust mechanical properties. HBPEC is a functional material that can be used to adjust the lower critical solution temperature (LCST) of the smart window over a wide range by changing the degree of substitution (DS) of the butoxy group in its structure. In addition, the use of HBPEC effectively improves the light transmittance and mechanical properties of the hydrogels. After 100 heating and cooling cycles, the hydrogel still has excellent stability. Furthermore, indoor simulation experiments show that HBPEC/PNIPAM hydrogel smart windows have better indoor temperature regulation capabilities than traditional windows, making these smart windows potential candidates for energy-saving building materials. Full article