Search Results (44)

Polymer-dispersed liquid crystal (PDLC), as an electrically controlled dimming material, has broad application prospects in various fields, including smart glass, display technology, and optical devices. However, traditional PDLC materials still face some challenges in practical applications, such as a high driving voltage and insufficient optical contrast, which limit their further application in high-performance optoelectronic devices. In this study, PDLC composite films exhibiting low-voltage operation (23 V), high contrast ratios (135), and rapid response times (T_R ~1.28 ms, T_D ~48 ms) were developed. This was achieved by modifying the chain length of the crosslinking agent and polymer monomer as well as by incorporating molybdenum disulfide (MoS₂) nanosheets. It shows a good regulation ability in the sunlight range (ΔT_sol = 63.92%, ΔT_lum = 73.97%). Simultaneously, the various chemical bonds inside the film and its special network structure enable it to exhibit a good radiative cooling effect. The indoor sunlight simulation tests showed that the indoor temperature decreased by 5 °C. This study provides valuable ideas for the development and preparation of smart windows with high efficiency and energy savings. Full article

Vanadium dioxide (VO₂) has become one of the most promising smart temperature-controlled thin-film materials due to its reversible phase transition between a metallic and an insulating state at approximately 68 °C, accompanied by negligible volume change and excellent optical modulation properties. However, the practical application of VO₂ is still limited by its relatively high phase transition temperature and susceptibility to oxidation. To address these two major shortcomings, this study employed a one-step hydrothermal method to prepare a VO₂ nanopowder, followed by a chemical precipitation method to form a VO₂@AlF₃ core–shell structure. The coated nanoparticles were then dispersed in a PVP ethanol solution, coated onto a glass substrate, and evaluated for performance. The experimental results indicate that when the molar ratio of VO₂ to AlF₃ reached 1:1, the phase transition temperature of VO₂@AlF₃ was effectively reduced to 50.3 °C, significantly lower than the original temperature of 68 °C. Additionally, the material exhibited favorable optical properties, with a solar modulation ability (ΔT_sol) of 17.2% and a luminous transmittance (T_lum) of 36.3%. After calcination in air at 300 °C for 3–6 h, the VO₂ core remained oxidation-resistant and maintained excellent phase-change thermal insulation properties. Full article

We consider light, high-absorbance, low-reflectance, electrically large layered sheet structures composed of thin carbon nanotube films. Such structures can be utilized in electromagnetic absorption and shielding applications in the X-band. They are of increasing interest in sensor-enabling technologies, stealth systems, and EMI shielding of electronic components. Especially in aerospace, this is crucial, as sensors are integral to aerospace engineering, enhancing the safety, efficiency, and performance of aircraft and spacecraft. To that end, sheets with carbon nanotube films embedded in a glass fiber polymer matrix are fabricated. The films have a thickness of around 70 μm. As shown, they cause a significant attenuation of the electromagnetic field. For shielding applications, a single-film sheet structure with total thickness of 1.65 mm presents an attenuation of around 25 dB in the transmission coefficient, while the attenuation can reach 37 dB for a two-film sheet structure with thickness of 1.8 mm. Shielding effectiveness performance is found to be greater than 35 dB for the two-film sheet structure. For applications requiring both high shielding and absorption, a two-layered structure with a thickness of 4.65 mm has been designed. The absorption, represented by the Loss Factor, is calculated to achieve values greater than 90%. The simulation results show good agreement with the measured data. The findings demonstrate a promising structure for materials suitable for sensor housings and smart electromagnetic environments where the suppression of electromagnetic interference is critical. In conclusion, the addition of carbon nanotube films, even at micrometer thicknesses, within a glass fiber polymer matrix significantly enhances both electromagnetic shielding and absorption performance. Full article

Broadband near-infrared (NIR) reflective films are widely used in architecture and the automotive and aerospace industries for energy saving and thermal regulation. For large-area and flexible applications, it is essential to develop cost-effective, solution-processable, and long-term-stable NIR-reflective films. Here, we present a polymer-stabilized chiral liquid crystal (CLC) film that achieves broadband NIR reflection by stacking opposite-handed CLC layers with pitch gradients. We experimentally established optimal formulations of materials for both right-handed and left-handed CLCs. The resulting film exhibits high-degree broadband reflection (~95%) in the 1000–1800 nm wavelength range, while maintaining visible transmittance (~80%) in the 450–850 nm range. The concept proposed here will be widely applicable for scalable and practical NIR-filtering applications in smart glasses, sensors, and optoelectronic devices. Full article

Electrochromic materials have a wide range of energy-effective applications, such as in mirrors, smart windows, automobile sunroofs, and display devices. The electrochromic behavior of mixed metal oxides is focused on in this review. Extra heat absorbed by buildings is one of the major problems in our modern era, so electrochromic films have been used as components of smart windows to reduce heat absorption through glass windows. Transition metal (W, V, Ti, Mo, and Ni) oxides are considered popular electrochromic materials for this purpose. Smart windows consist of electrochromic material layers (such as metal oxide layers) and solid electrolytes sandwiched between transparent conductive layers. Few publications have studied the use of mixtures of different metal oxides as electrochromic materials. This study focuses on the results of investigations of such multicomponent materials, such as the effects on the electrochromic properties of mixed metal oxides and how they contrast with pure metal oxides. Reviewing these papers, we found WO₃- and MoO₃-based mixtures to be the most promising, especially the magnetron-sputtered, amorphous WO₃(40%)–MoO₃(60%) composition, which had 200–300 cm²/C coloration efficiency. The mixed oxide materials reported in this review have room for development (and even commercialization) in the oxide-based electrochromic device market. Full article

We investigated patterns formed during the polymerization process of bifunctional monomers in a liquid crystal for both large polymer concentrations (polymer-dispersed liquid crystals, PDLC) and small concentrations (polymer-stabilized liquid crystals, PSLC). The resulting experimental patterns are reminiscent of Voronoi diagrams, so a reverse Voronoi algorithm was developed that provides the seed locations of cells, thus allowing a computational reproduction of the experimental patterns. Several metrics were developed to quantify the commonality between the faithful experimental patterns and the idealized and generated ones. This led to descriptions of the experimental patterns with accuracies better than 90% and showed that the curvature or concavity of the cell edges was below 2%. Possible reasons for the discrepancies between the original and generated Voronoi diagrams are discussed. The introduced algorithm and quantification of the patterns could be transferred to many other experimental problems, for example, melting of thin polymer films, ultra-thin metal films, or bio-membranes. The discrepancies between the experimental and ideal Voronoi diagrams are quantified, which may be useful in the quality control of privacy windows, reflective displays, or smart glass. Full article

This study introduces the development of a W-M_1.0 electrochromic film, characterized by a “coral”-like TiO₂@WO₃ heterostructure, synthesized via a hydrothermal process leveraging the inherent instability of MXene. The film showcases exceptional electrochromic performance, with a coloring response time of 2.8 s, a bleaching response time of 4.6 s, and a high coloring efficiency of 137.02 cm²C⁻¹. It also demonstrates a superior light modulation ability of 73.83% at 1033 nm. Notably, the W-M_1.0 film exhibits remarkable cyclic stability, retaining over 90% of its initial light modulation capacity after 4000 cycles, outperforming many existing electrochromic materials. The film’s enhanced performance is credited to its coral-like structure, which boosts the specific surface area and promotes ion transport, and the TiO₂@WO₃ heterojunctions, which enhance charge transfer and stabilize the material. Devices fabricated with the W-M_1.0 film as the cathode and a PB film as the anode exhibit a seamless transition from dark blue to colorless, underscoring their potential for smart window and dynamic glass applications. Full article

Poly(N-isopropylacrylamide) (PNIPAM) offers a promising platform for non-invasive and gentle cell detachment. However, conventional PNIPAM-based substrates often suffer from limitations including limited stability and reduced reusability, which hinder their widespread adoption in biomedical applications. In this study, PNIPAM copolymer films were formed on the surfaces of glass slides or silicon wafers using a two-step film-forming method involving coating and grafting. Subsequently, a comprehensive analysis of the films’ surface wettability, topography, and thickness was conducted using a variety of techniques, including contact angle analysis, atomic force microscopy (AFM), and ellipsometric measurements. Bone marrow mesenchymal stem cells (BMMSCs) were then seeded onto PNIPAM copolymer films prepared from different copolymer solution concentrations, ranging from 0.2 to 10 mg·mL⁻¹, to select the optimal culture substrate that allowed for good cell growth at 37 °C and effective cell detachment through temperature reduction. Furthermore, the stability and reusability of the optimal copolymer films were assessed. Finally, AFM and X-ray photoelectron spectroscopy (XPS) were employed to examine the surface morphology and elemental composition of the copolymer films after two rounds of BMMSC adhesion and detachment. The findings revealed that the surface properties and overall characteristics of PNIPAM copolymer films varied significantly with the solution concentration. Based on the selection criteria, the copolymer films derived from 1 mg·mL⁻¹ solution were identified as the optimal culture substrates for BMMSCs. After two rounds of cellular adhesion and detachment, some proteins remained on the film surfaces, acting as a foundation for subsequent cellular re-adhesion and growth, thereby implicitly corroborating the practicability and reusability of the copolymer films. This study not only introduces a stable and efficient platform for stem cell culture and harvesting but also represents a significant advance in the fabrication of smart materials tailored for biomedical applications. 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

Electrochromism has emerged as a pivotal technology in the pursuit of energy efficiency and environmental sustainability, spurring significant research efforts aimed at the creation of advanced electrochromic devices. Most electrochromic materials are used for smart window applications. However, current electrochromic materials have been applied to new energy vehicles, cell phone back covers, AR glasses, and so on. More application scenarios put forward more requirements for the color of the colored states. Choosing the right color change in the application will be the trend in the future. In this work, tungsten trioxide (WO₃) thin films were prepared by adjusting the in situ heating temperature. WO₃ with a crystalline structure showed excellent cyclic stability (5000 cycles), electrochromic performance (ΔT = 77.7% at 633 nm, CE = 37.1 cm²/C), relatively fast bleaching/coloring speed (20.0 s/19.4 s), and the darkest coloring effect (L* = 29.32, a* = 7.41, b* = −22.12 for the colored state). These findings offer valuable insights into the manipulation of smart materials and devices, contributing to the advancement of electrochromic technology. Full article

In this study, we present a 5,8-bis(3,4-ethylenedioxythiophene)quinoxaline monomer with two 4-(octyloxy)phenyl side chains (EDOTPQ) that can be electropolymerized on ITO glass in standard electrolytes containing lithium salts and propylene carbonate as solvent. The electrochemically deposited PEDOTPQ layers show very good adhesion and homogeneity on ITO. The green-colored polymer thin films exhibit promising electrochromic (EC) properties and are interesting for applications such as adaptive camouflage, as well as smart displays, labels, and sensors. Novel organic–inorganic (hybrid) EC cell configurations were realized with Prussian blue (PB) or titanium-vanadium oxide (TiVO_x) as ion storage electrodes, showing a highly reversible and fast color change from green to light yellow. Full article

A polymer-stabilized liquid crystal (PSLC) device has been a promising candidate in several scenarios like smart vehicle windows and glass curtain walls in recent years due to its remarkable features like a fast switch from the initial transparent state to the scattering state with a rather low driving voltage, high transmittance at off-state, and broad viewing angle. The electro-optical characteristics of PSLC devices are determined by the synergistic attributions of liquid crystal (LC) molecules and the influence of the polymer network exerted on the movement of LC molecules. A systematic study of the influence of the polymer network on the movement of LC molecules is conducted, with the polymer network formed by methoxy/cyano/carboxyl monomers and diacrylate C6M. The polymer network morphology of PSLC film is greatly affected by the molecular structures and content of monoacrylic monomers. Additionally, the electro-optical performance and peel strength of PSLC films could be improved by modulating the molecular structures and morphology of polymer networks. PSLC devices containing carboxyl monomers show enhanced electro-optical performance and peel strength due to their directional filiform topology. This study might provide guidance for optimizing the performance of PSLC devices and establishing the relationship between the molecular structure, polymer network morphology, and electro-optical performance of reverse-mode dimming films. Full article

Polymer-dispersed liquid-crystal (PDLC) films have wide applications in light shutters, smart windows for cars and buildings, dimming glasses, and smart peep-proof films due to their switchable optical states under electrical fields as well as large area processibility. They are usually prepared with liquid crystals (LCs) and non-liquid crystalline monomers (NLCMs). Introduction of liquid crystalline monomers (LCMs) into PDLCs might spark new functionality or high-performance devices such as polymer-dispersed and -stabilized liquid crystals. In this study, the effect of molecular structures and doping concentrations of acrylate LCMs on the electro-optical properties and micro-structures of PDLC films is systematically studied. The pore size of polymer networks and the driving voltage of the PDLC films are affected by the molecular polarity and degree of functionality of the LCMs. The electro-optical properties of the PDLC films are affected by the synergistic influence of molecular structure of LCMs and micro-structures of PDLCs. These results might provide the experimental and theoretical basis for constructing the relationship between the molecular structure of LCM, micro-structure and electro-optical response of PDLC films. Full article

Polymer-dispersed liquid crystal (PDLC) film is an active smart film penetrating the market due to its unique functionalities. These functional characteristics include switchable tint capabilities, which shield building residents from the sun’s harmful ultraviolet (UV) rays, improve energy-saving features, and produce higher cost-efficiency. Although PDLC films are promising in several applications, there is still ambiguity on the performance of PDLC films. Particularly, the sizing effects’ (such as film thickness and area) correlation with visible light transmission (VLT), ultraviolet rejection (UVR), infrared rejection (IRR), light intensity, current consumption, and apparent power consumption is not well understood. Therefore, this study investigated the sizing effects of PDLC films, including the thickness effect on VLT, UVR, IRR, light intensity, and area influence on current and apparent power consumptions. The varying applied voltage effect on the light transmittance of the PDLC film was also effectively demonstrated. A 0.1 mm PDLC film was successfully presented as a cost-efficient film with optimal parameters. Consequently, this study paves the way for a clearer understanding of PDLC films (behavior and sizing effects) in implementing economic PDLC films for large-scale adoption in commercial and residential premises. Full article

Electrochromic (EC) windows on glass for thermal and glare protection in buildings, often referred to as smart (dimmable) windows, are commercially available, along with rearview mirrors or windows in aircraft cabins. Plastic-based applications, such as ski goggles, visors and car windows, that require lightweight, three-dimensional (3D) geometry and high-throughput manufacturing are still under development. To produce such EC devices (ECDs), a flexible EC film could be integrated into a back injection molding process, where the films are processed into compact 3D geometries in a single automized step at a low processing time. Polycarbonate (PC) as a substrate is a lightweight and robust alternative to glass due to its outstanding optical and mechanical properties. In this study, an EC film on a PC substrate was fabricated and characterized for the first time. To achieve a highly transmissive and colorless bright state, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) was used as the working electrode, while titanium dioxide (TiO₂) was used as the counter electrode material. They were deposited onto ITO-coated PC films using dip- and slot-die coating, respectively. The electrodes were optically and electrochemically characterized. An ECD with a polyurethane containing gel electrolyte was investigated with regard to optical properties, switching speed and cycling behavior. The ECD exhibits a color-neutral and highly transmissive bright state with a visible light transmittance of 74% and a bluish-colored state of 64%, a fast switching speed (7 s/4 s for bleaching/coloring) and a moderately stable cycling behavior over 500 cycles with a decrease in transmittance change from 10%to 7%. Full article