Smart Windows Research Articles

Advancements in MEMS Micromirror and Microshutter Arrays for Light Transmission Through a Substrate

This paper reviews and compares electrostatically actuated MEMS (micro-electro-mechanical system) arrays for light modulation and light steering in which transmission through the substrate is required. A comprehensive comparison of the technical achievements of micromirror arrays and microshutter arrays is provided. The main focus of this paper is MEMS micromirror arrays for smart glass in building windows and façades. This technology utilizes millions of miniaturized and actuatable micromirrors on transparent substrates, enabling use with transmissive substrates such as smart windows for personalized daylight steering, energy saving, and heat management in buildings. For the first time, subfield-addressable MEMS micromirror arrays with an area of nearly 1 m2 are presented. The recent advancements in MEMS smart glass technology for daylight steering are discussed, focusing on aspects like the switching speed, scalability, transmission, lifetime study, and reliability of micromirror arrays. Finally, simulations demonstrating the potential yearly energy savings for investments in MEMS smart glazing are presented, including a comparison to traditional automated external blind systems in a model office room with definite user interactions throughout the year. Additionally, this platform technology with planarized MEMS elements can be used for laser safety goggles to shield pilots, tram, and bus drivers as well as security personal from laser threats, and is also presented in this paper.

Effects of thiols on electro-optical properties of reverse polymer-stabilised liquid crystal films

ABSTRACT Reverse-mode polymer stabilised liquid crystal (RPSLC) can maintain a transparent state without voltage and exhibit excellent light scattering haze performance when voltage is applied, making it suitable for long-term use in smart windows. However, the high operating voltage of polymer stabilised liquid crystal devices necessitates efforts to reduce the driving voltage and enhance the contrast ratio to improve their optical properties. In this paper, we demonstrate that the introduction of a small amount of the thiol monomer into acrylate polymer monomer during UV-induced homopolymerisation and copolymerisation significantly affects the crosslinking density of the polymer network, thereby influencing the electro-optic performance of RPSLC devices. As a result, we have developed a high-contrast RPSLC device with a saturation voltage below 10 V. These findings are crucial for guiding practical improvements in the performance of RPSLC device.

Cholesteric liquid crystal mixtures for the switchable smart windows and light shutters: Electro-optical and dielectric behaviour

Abstract Cholesteric liquid crystal (CLC) mixtures with variable pitch lengths were prepared for the electrical switchable smart window and light shutter applications by taking varied concentrations (2.6, 3.0, 4.0, and 5.0 wt%) of chiral dopant (R1011) having helical twisting power (HTP) 37.6 μm−1 and nematic E7 liquid crystal (LC). The morphological and electro-optical analysis of these CLC mixtures filled in 10µm thick cells were observed and reported herein, the switching of initial planar (P) and initial focal conic (FC) to homeotropic (H) states as well as vice-versa. The operating voltage of the 2.6 wt% of chiral doped CLC cell was relatively lower among all the sample cells compared with other concentrations. The maximum contrast ratio (CR) was observed for 5.0 wt% chiral doped CLC cell with initial planar state. However, the best CR was observed in 2.6wt% CLC cell with initial FC state. The comparative macroscopic views of the P, FC, and H states in the OFF and ON conditions of applied voltage for prepared CLC cells were observed for transparent and opaque states. Further, UV-visible spectroscopy was performed in the P, FC, and H states under the application of an externally applied field to observe the absorbance and band gap behavior of the fabricated CLC cells. Additionally, chiral concentration-dependent dielectric parameters with variable frequency in initial P and FC states of the fabricated cells were also reported. The temperature-dependent phase behavior of all the prepared cells exhibited a slight decrease in the isotropic phase of LC due to the doping of chiral dopants.

Performance on Activities of Daily Living and User Experience When Using Artificial Intelligence by Individuals With Vision Impairment.

This study assessed objective performance, usability, and acceptance of artificial intelligence (AI) by people with vision impairment. The goal was to provide evidence-based data to enhance technology selection for people with vision loss (PVL) based on their loss and needs. Using a cross-sectional, counterbalanced, cross-over study involving 25 PVL, we compared performance using two smart glasses (OrCam and Envision Glasses) and two AI apps (Seeing AI and Google Lookout). We refer to these as assistive artificial intelligence implementations (AAIIs). Completion and timing were quantified for three task categories: text, text in columns, and searching and identifying. Usability was evaluated with the System Usability Scale (SUS). The odds ratios (ORs) of being able to complete Text tasks were significantly higher when using AAIIs compared to the baseline. OR when performing "Searching and Identifying" tasks varied among AAIIs, with Seeing AI and Envision improving the performance of more tasks than Lookout or OrCam. Participants expressed high satisfaction with the AAIIs. Despite the findings that performance on some tasks and when using some AAIIs did not result in a greater number of PVL being able to complete the tasks, there was overall high satisfaction, reflecting an acceptance of AI as an assistive technology and the promise of this developing technology. This evidence-based performance data provide guidelines for clinicians when recommending an AAII to PVL.

Electrically Switchable Multi-Stable Topological States Enabled by Surface-Induced Frustration in Nematic Liquid Crystal Cells.

In liquid crystal (LC) cells, the surface patterning directs the self-assembly of the uniaxial building blocks in the bulk, enabling the design of stimuli-response optical devices with various functionalities. The combination of different anchoring patterns at both substrates can lead to surface induced frustration, preventing a purely planar and defect-free configuration. In cells with crossed assembly of rotating anchoring patterns, elastic deformations allow to obtain a defect-free bulk configuration, but an electrical stimulus can induce disclination lines. The disclination network is preserved without applied voltage. Depending on the electric field treatment and geometrical parameters, different multi-stable states with and without disclinations are obtained. This is demonstrated with the help of dual-frequency LCs, for which the frequency dependent dielectric properties allow repeatable switching between multi-stable states. Topological protection and the associated energy barrier between different states explains the observed metastability. The obtained configurations are retrieved with Q-tensor simulations and the validity is confirmed by matching optical simulations with experimentally obtained microscopy images. The realized multi-stable topological states interact differently with light, resulting in distinct optical properties. Optimization allows to switch between a highly transparent state and an opaque state, opening up opportunities for smart windows with low energy consumption.

Revolutionizing Dual-Band Modulation and Superior Cycling Stability in GDQDs-Doped WO3 Electrochromic Films for Advanced Smart Window Applications.

Dual-band tungsten oxide (WO3) electrochromic films are extensively investigated, yet challenges persist regarding complex fabrication processesand limited cyclic stability. In this paper, a novel approach to prepare graphdiyne quantum dots (GDQDs) doped WO3 films with a hexagonal crystal structure, is presented. Structural characterization reveals that the GDQDs/WO3 possesses a coral-like, loose structure with high crystallinity due to the synergistic modulation of morphology and crystallinity. Electrochemical tests confirm that this unique structure provides abundant multi-active sites and efficient electrolyte ion channels, which facilitate the ion insertion/extraction to promote the electrochromic process. The GDQDs/WO3 films exhabit impressive electrochromic performance, with rapid swithing (12.6/8.4 s for bleaching/coloration), high coloring efficiency (104.78 cm2C-1 at 1100nm), and independent dual-band transmittance changes (ΔT， with ΔT633nm = 64.54%, ΔT1100nm = 83.52% and ΔT1600nm = 79.80%), and exceptional stability (remained 95.1% modulation range after 20 000 cycles). The unique characteristics of GDQDs lead to the formation of a built-in electric field via charge transfer, which optimizes and enriches the energy level structure of WO3. This solution not only advances the development of electrochromic technology, but also opens the door for future innovative applications of smart materials.

Smart windows with high optical transparency and structural color

Smart windows with high optical transparency and structural color

Recent advances in flexible multifunctional electrochromic devices.

Electrochromism refers to the phenomenon in which certain materials undergo a redox reaction under an applied voltage or current, resulting in reversible changes in their optical properties and color appearance. Electrochromic devices (ECDs) show great potential in smart windows, anti-glare rear-view mirrors and displays due to the advantages of low energy consumption and simple control mechanisms. However, traditional ECDs are unfavorable for wearable and deformable optoelectronics due to the structural rigidity and limited functions. Thus, flexible ECDs integrating visual information with other advanced technologies can realize multifunctionality and further expand their application fields. This review first introduces the structure and recent development of flexible ECDs, followed by comprehensively summarizing the recent development of flexible multifunctional ECDs, including energy harvesting, energy storage, multicolor displays, and smart windows. Finally, the challenges, development trends and future prospects in flexible multifunctional ECDs are proposed and discussed. We hope that this review can guide and accelerate the development of flexible multifunctional ECDs in the new era of smart optoelectronics.

A bifunctional self-powered electrochromic and thermochromic smart window with enhanced privacy protection ability

A bifunctional self-powered chromic smart window can achieve four distinct states: a highly transparent state, a milky white state (thermochromic), a blue color state (electrochromic), and a nontransparent state (the dual-color private state).

Optimizing transition temperatures for thermochromic smart windows via neural networks coupling simulation

Optimizing transition temperatures for thermochromic smart windows via neural networks coupling simulation

Effect of VO2 particle aggregation on the performance of thermochromic smart window films for building

Effect of VO2 particle aggregation on the performance of thermochromic smart window films for building

Crystal reconstructed cubic nickel oxide with energetic reactive interfaces for exceptional electrochromic smart windows

The reconstruction of cubic phase NiO by phosphorylation extremely improves ion transport efficiency and electrochromic properties.

Crucial impact of spectrum calculation on energy and daylighting performance of glazing windows

The rapid advancement of spectrally selective materials has enabled the development of smart windows that can regulate different bands of solar radiation. However, existing methods for calculating spectral properties vary, leading to inconsistent results when evaluating their light-electricity-heat-color performance. Therefore, this paper presents five methods for calculating window spectral properties, intending to compare and identify the most effective approach for assessing building thermal performance, energy efficiency, and daylighting. The methods focus primarily on the solar spectrum input and the glazing spectrum response. The solar spectrum inputs include the Beijing local solar spectrum, ASTM G173-03, and ISO 9845 (methods S1 to S3), and the glazing spectrum response methods differ based on whether they account for spectral selectivity and the choice of spectral weighting functions (methods S3 to S5). The findings reveal that variations in solar spectrum input have a minimal effect on window performance, while differences in glazing spectral response calculations significantly impact results. It is particularly evident in thermochromic windows, where discrepancies in energy efficiency, specifically in lighting load, can reach up to 67.21 %, and variations in dynamic daylighting performance, specifically in Useful Daylight Illuminance (UDI) below 500 lx, can be as high as 28.27 %. To provide more accurate assessment results of glazing windows, this study recommends using the spectral calculation method S1, which incorporates the local solar spectrum and applies the standard luminous efficiency function to the glazing spectrum response. This paper highlights that further refinement of spectral calculation methods will enhance their utility for performance evaluation and guide the reverse design of innovative window features.

A Novel Liquid Flow Electrochromic Smart Window for All-year-round Dynamic Photothermal Regulation

A Novel Liquid Flow Electrochromic Smart Window for All-year-round Dynamic Photothermal Regulation

Eco-friendly innovation: three-mode sun-actuated thermotropic devices integrating κ-carrageenan-based film doped with Arundo donax leaf-derived carbon dots and 1-butyl-3-methyl-1H-imidazolium chloride

This study develops eco-friendly sun-activated thermotropic devices by incorporating carbon dots derived from Arundo donax leaves, and ionic liquid into kappa-carrageenan films. These CD-doped films offer great promise for zero-energy smart windows.

Efficient Electrochromic Electrode Materials Based on WO3/Ni(OH)2 with Dual Ion Implantation Modulability and Energy Level Matching

AbstractElectrochromic materials have received a lot of attention due to dramatic growth of the smart window market and the demand in various emerging fields. In this study, WO3/Ni(OH)2 composite high efficient electrochromic electrode materials are prepared by hydrothermal‐annealing and electrodeposition methods. It is observed by experimental characterization that the deposition of Ni(OH)2 on WO3 rods effectively increased the Li+ diffusion rate of WO3 films (2.069 × 10−10 cm2 s−1), which is ≈1.5 times higher than that of pure WO3 (1.413 × 10−10 cm2 s−1). Meanwhile, WO3 and Ni(OH)2 have relatively matched energy level structures, showing high overall optical modulation performance. In addition, density functional theory (DFT) calculations combined with electrochemical studies reveal that the injection of double ions can improve the reaction efficiency of the electrodes and promote the redox reaction, which makes the electrochemical reaction more efficient. This paper provides a practical method for designing multi‐component electrochromic devices with excellent performance.

Application of rhodamine B as thermochromic sensor for evaluation of performance of cold paint

A thermochromic pigment, derived from reaction of ethylenediamine and rhodamine B known as MA-RB, has been successfully developed. This pigment showcases temperature-controlled visible color-transformation properties in both solid and solution states. The thermochromic pigment MA-RB exhibits a notable color change from light pink to rose red, triggered by thermal excitation. In its solid form, MA-RB also displays thermochromic behavior, shifting its color from pink to rose red when exposed to visible light. MA-RB distinct thermochromic properties, characterized by visible color changes, make it a promising material for applications in both solid and liquid systems. Its ability to respond to temperature changes makes it an attractive option for coatings, offering a non-intrusive alternative for temperature measurement. It is successfully applied to measure the performance of cold paint which contains coumarin derivate as cold pigment. This can open a new filed in application of thermochromic pigments in energy systems such as smart windows, wearable fabrics, etc. or in measurement devices of temperature.

High photothermal conversion efficiency of RF sputtered Ti4O7 Magneli phase thin films and its linear correlation with light absorption capacity

RF-sputtering is used to deposit Ti4O7-Magneli-phase films onto various substrates at deposition temperatures (Ts) ranging from 25 to 650 °C. Not only the structural, but also electrical conductivity, optical absorbance and photothermal properties of the Ti4O7 films are shown to change significantly with Ts. A Ts of 500 °C is pointed out as the optimal temperature that yields highly-crystalized pure-Ti4O7-Magneli phase with a densely-packed morphology and a conductivity as high as 740 S/cm. The Ti4O7 films deposited at Ts = 450–500 °C also exhibited the highest optical absorption over all the broad (200–1500) nm range. The absorbed sunlight (AM1.5) was efficiently converted into heat by raising the temperature of the Ti4O7 films up to ~ 54 °C. Thus, the external photothermal efficiency (ηext) of the Ti4O7 films, was found to be as high as ~ 74%. This is the highest ηext reported so far for sputtered-Ti4O7 coatings (just ~ 450 nm-thick), highlighting their significant potential for photothermal applications such as desalination, deicing and/or smart windows. Finally, the ηext of the Ti4O7 coatings is demonstrated, for the first time, to be linearly correlated to their integrated light absorption coefficient. This fundamental relationship paves the way towards the design and optimization of highly efficient solar-thermal conversion devices.

Molybdenum Trioxide/Poly Vinyl Alcohol Polymer Nanocomposites: An Investigation of Structural, Optical, Mechanical and Photochromic Properties for Application in Smart Windows

ABSTRACTThe current work elucidates the investigation of optical, mechanical and photochromic behavior of molybdenum trioxide (MoO3) reinforced polyvinyl alcohol (PVA) (MoO3/PVA) nanocomposites (NCs) under the effect of changing UV exposure time as well as increasing wt% of nanofiller. For synthesizing self‐supporting and flexible MoO3/PVA NCs, solution‐casting technique was employed while MoO3 was synthesized using hydrothermal treatment. X‐Ray Diffraction (XRD) confirms the orthorhombic phase while transmission electron microscopy (TEM) and scanning electron microscopy (SEM) illustrates the sheet‐like morphology of MoO3. The calculated optical band gap (Eg) of PVA decreases from 4.83 0.16 eV to 2.77 0.06 whereas the refractive index (n) increases from 1.46 to 2.04 after embedding 10 wt% of MoO3. The young's modulus for PVA was found to increase from 102.33 to 192.68 MPa after incorporation of 10 wt% of nanofiller. The photochromic studies reveal that the maximum optical modulation (relative reflectance % value ~19.08) and maximum coloration efficiency (~0.0916) corresponds to 10 wt% MoO3/PVA NC. Thus, the ability of fabricated NCs to modulate solar light transmittance automatically in response to UV exposure and reduce energy consumption by adjusting the indoor atmosphere makes them a highly sought‐after choice for ‘photochromic smart windows’.

Progress in Tungsten Trioxide-Based Materials for Energy Storage and Smart Window Applications

Previous years have witnessed a rapid surge in WO3-based experimental reports for the construction of energy storage devices (ESDs) and electrochromic devices (ECDs). WO3 is a highly electrochromic (EC) material with a wide band gap that has been extensively used for the construction of working electrodes for supercapacitor (SC) and ECD applications. Previously, WO3-based hybrid composites were explored for SC and ECD applications. In this review report, we have compiled the WO3-based hybrid electrode materials for SC and ECD applications. It is believed that the present review would benefit the researchers working on the fabrication of electrode materials for SC and ECD applications. In this review article, challenges and future perspectives have been discussed for the development of WO3-based SCs and ECDs.