Smart Coatings Research Articles

Customized designs, preparations, and characterizations of high-performance multilayer VO2-based thermochromic smart coatings

VO2-based thermochromic coatings have gained much attention in temperature-adaptive smart windows, and constructing multilayer film structures is the main way to obtain high thermochromic performances. Based on the self-developed objective-orientated automatic optimization code, the present research realized customized designs of thermochromic multilayer coatings composed of VO2, TiO2, and SiO2 from the objectives of visible luminance (Tlum) and solar light modulation (ΔTsol). The TiO2/VO2/s, VO2/TiO2/s, TiO2/VO2/TiO2/s, and SiO2/TiO2/VO2/TiO2/s (s denotes substrate) multilayer film systems were then prepared by magnetron sputtering and vacuum controllable heating, with their structures, insulator-metallic transition, and thermochromic properties being carefully studied. The result showed that the best trade-off between high Tlum and high ΔTsol was achieved for these film assemblies, and solar light modulation was mainly limited at the near-IR wavelength region of the solar spectrum, with the difference between cool- and hot-state Tlum being greatly reduced. In the case of the four-layer SiO2/TiO2/VO2/TiO2/s, very high average Tlum (60%) and high ΔTsol (14%) were obtained. A 100 × 100 mm2 of the SiO2/TiO2/VO2/TiO2/s was also prepared, and it showed an obvious temperature adjustment, and the service life can last for 14 years under normal weather conditions. Not limited to the prepared multilayer film systems, the methodology used here is also suitable for the fast development of other multilayer film systems.

Smart and UV-Resistant Edible Coating and Films Based on Alginate, Whey Protein, and Curcumin.

In this work, smart edible coating and films with excellent UV barrier properties were prepared from alginate, whey protein isolate, and curcumin. The primary focus of this investigation centered on assessing the impact of whey protein and curcumin on the physical and functional properties of the alginate films. Whey protein reduced the film transparency while simultaneously enhancing the hydrophobicity and antioxidant properties of the alginate film. Curcumin imparted a yellow hue to the film, consequently decreasing the transparency of the film. It also substantially improved hydrophobicity, antioxidant activity, and UV-blocking efficiency within the films. Remarkably, curcumin demonstrated a significant reduction in the water vapor transmission rate of the film. For the preservation of apples, a higher concentration of curcumin was required, which effectively suppressed the respiration rate and moisture loss post-harvest, resulting in an extended shelf-life for the apples. As a result, the coated apples exhibited significantly reduced enzymatic browning and weight loss in comparison to their uncoated counterparts. Furthermore, these curcumin-containing films underwent a reversible color change from orange to red when exposed to ammonia vapor. This attribute highlights the potential of the developed coating and film as a smart, active food packaging solution, particularly for light-sensitive food products.

Towards Room Temperature Thermochromic Coatings with controllable NIR-IR modulation for solar heat management & smart windows applications

Solar heat management & green air-conditioning are among the major technologies that could mitigate heat islands phenomenon while minimizing significantly the CO2 global foot-print within the building & automotive sectors. Chromogenic materials in general, and thermochromic smart coatings especially are promising candidates that consent a noteworthy dynamic solar radiation Infrared (NIR-IR) regulation and hence an efficient solar heat management especially with the expected increase of the global seasonal temperature. Within this contribution, two major challenging bottlenecks in vanadium oxide based smart coatings were addressed. It is validated for the first time that the NIR-IR modulation of the optical transmission (∆TTRANS = T(T〈TMIT) − T(T〉TMIT) of Vanadium oxide based smart coatings can be controlled & tuned. This upmost challenging bottle-neck controllability/tunability is confirmed via a genuine approach alongside to a simultaneous drastic reduction of the phase transition temperature TMIT from 68.8 °C to nearly room temperature. More precisely, a substantial thermochromism in multilayered V2O5/V/V2O5 stacks equivalent to that of standard pure VO2 thin films but with a far lower transition temperature, is reported. Such a multilayered V2O5/V/V2O5 thermochromic system exhibited a net control & tunability of the optical transmission modulation in the NIR-IR (∆TTRANS) via the nano-scaled thickness’ control of the intermediate Vanadium layer. In addition, the control of ∆TTRANS is accompanied by a tremendous diminution of the thermochromic transition temperature from the elevated bulk value of 68.8 °C to the range of 27.5–37.5 ºC. The observed remarkable and reversible thermochromism in such multilayered nano-scaled system of V2O5/V/V2O5 is likely to be ascribed to a noteworthy interfacial diffusion, and an indirect doping by alkaline ions diffusing from the borosilicate substrate. It is hoped that the current findings would contribute in advancing thermochromic smart window technology and their applications for solar heat management in glass windows in general, skyscraper especially & in the automotive industry. If so, this would open a path to a sustainable green air-conditioning with zero-energy input.

Electrospinning of glass nanofibers to roughen a waterborne polyurethane coating toward smart applications

Polyurethane (PU) coating bulk was reinforced with electrospun glass nanofibers (GNF) and nanoparticles of lanthanide-doped strontium aluminate (NLSA) to produce mechanically reliable long-lasting photoluminescent and photochromic smart products. Transparent smart coatings of GNF@PU were prepared by the physical integration of lanthanide-doped strontium aluminate nanoparticles. The transparent appearance of GNF@PU was found to shift to green when exposed to ultraviolet light as proved by spectral examinations using photoluminescence and CIE Lab parameters. Fluorescence emission with instantaneous reversibility was monitored for GNF@PU hybrids with trace amounts of NLSA. Afterglow photoluminescence with slow reversibility was observed at higher phosphor concentrations in the GNF@PU hybrids. The coating hybrids revealed an emission band at 517 nm when excited at 365 nm. Transmission electron microscopic (TEM) analysis of the morphological properties of NLSA and GNF showed diameters of 8–12 nm and 75–250 nm, respectively. After being fabricated by electrospinning technique, GNF were incorporated into polyurethane coatings as a roughening agent. X-ray fluorescence (XRF), energy-dispersive X-ray (EDX), and scanning electron microscope (SEM) were used to investigate the morphological features of GNF and smart coatings of GNF@PU. Scratch resistance of smart coatings was found to be higher than that of NLSA-free polyurethane control sample. Both of hydrophobicity and UV resistance improved with an increase in NLSA content.

Montmorillonite (MMT) nanoclay in smart coatings for corrosion protection of metal alloy: a brief review

Montmorillonite (MMT) nanoclay is a natural raw material naturally occurring 2-dimensional lamellar silicate material. Many advantages of MMT clay are low cost, high dispersion properties, good mechanical properties, hydrophobic, good shield against corrosive media, non-toxic, easily accessible, and most importantly, it is natural. MMT was mainly used as an additive with other active smart materials to enhance the excellent properties for smart coatings. However, there is not much research done from the last 5 years regarding MMT in smart coating for corrosion protection. The discussion regarding MMT for corrosion protection is also contradict between each research. This paper provides a brief review on MMT clay in smart coatings and its advantages for corrosion protection for the last 5 years. There are also some drawbacks of MMT in smart coatings discussed at the end. Further research needs to be done as MMT has more potential that can be used in the real-world industries and to clarify the contradiction of statement existed in much research.

Research on advanced photoresponsive azobenzene hydrogels with push-pull electronic effects: a breakthrough in photoswitchable adhesive technologies.

Smart materials that adapt to various stimuli, such as light, hold immense potential across many fields. Photoresponsive molecules like azobenzenes, which undergo E-Z photoisomerization when exposed to light, are particularly valuable for applications in smart coatings, light-controlled adhesives, and photoresists in semiconductors and integrated circuits. Despite advances in using azobenzene moieties for stimuli-responsive adhesives, the role of push-pull electronic effects in regulating reversible adhesion remains largely unexplored. In this study, we investigate for the first time photo-controlled hydrogel adhesives of azobenzene with different push-pull electronic groups. We synthesized the monomers 4-methoxyazobenzene acrylate (ABOMe), azobenzene acrylate (ABH), and 4-nitroazobenzene acrylate (ABNO2), and examined their effects on reversible adhesion properties. By incorporating these azobenzene monomers into acrylamide, dialdehyde-functionalized poly(ethylene glycol), and [3-(methacryloylamino)propyl]-trimethylammonium chloride, we prepared ABOMe, ABH, and ABNO2 ionic hydrogels. Our research findings demonstrate that only the ABOMe ionic hydrogel exhibits reversible adhesion. This is due to its distinct transition state mechanism compared to ABH and ABNO2, which enables efficient E-Z photoisomerization and drives its reversible adhesion properties. Notably, the ABOMe ionic hydrogel reveals an outstanding skin adhesion strength of 360.7 ± 10.1 kPa, surpassing values reported in current literature. This exceptional adhesion is attributed to Schiff base reactions, monopole-quadrupole interactions, π-π interactions, and hydrogen bonding with skin amino acids. Additionally, the ABOMe hydrogel exhibits excellent reversible self-healing capabilities, significantly enhancing its potential for injectable medical applications. This research underscores the importance of integrating multifunctional properties into a single system, opening new possibilities for innovative and durable adhesive materials.

Advances in modified silica nanoparticles utilization for various applications: Now and future

The review article explores the multifaceted applications of silica nanoparticles (SNPs) across diverse industries, emphasizing their catalytic role in transformative advancements. Green nanotechnology principles are crucial for sustainable SNP synthesis, with a focus on utilizing natural extracts and bio-agents. Standardization and enhanced collaboration between industry and academia are pivotal for realizing the broader potential of SNPs. In the biomedical realm, SNPs exhibit exceptional capabilities in drug delivery and diagnostics, promising significant medical advancements. Safe integration necessitates collaborative efforts in safety assessments, long-term studies, and standardized testing. The exploration of SNP-based advanced coatings hints at industry-specific applications, with a recommendation for continued research into new capabilities and compatibility. SNPs in Li-ion batteries show promise for energy storage, urging further investigation into scalability and long-term performance. Agriculture benefits from SNP applications in precision farming, emphasizing the need for environmentally conscious formulations. In nanocomposite materials, SNPs enhance mechanical properties, advocating collaborative research for standardization and optimization. The adaptability of SNP-based smart coatings in aerospace and automotive industries requires exploration of new functionalities and seamless integration. In conclusion, SNPs hold promising prospects in healthcare, energy storage, and agriculture, emphasizing the necessity of collaborative efforts, sustained research, and a commitment to responsible and innovative SNP integration for a technologically advanced and environmentally conscious future.

Augmented Reality-Enhanced Microwave-Based Wireless Monitoring System for Smart Coating Applications

Augmented Reality-Enhanced Microwave-Based Wireless Monitoring System for Smart Coating Applications

Unlocking Multifunctional Advantages with Nanocomposites Coatings for Solar Cells: A Comprehensive Review

Abstract: Nanocomposite coatings have garnered considerable attention as a versatile and innovative solution for addressing the challenges faced by solar cell technologies. This review article provides a comprehensive overview of the multifunctional advantages that nanocomposite coatings offer in the realm of solar cell technology. Furthermore, it delves into the myriad benefits that nanocomposite coatings bring to the table, including enhanced light absorption, improved charge carrier dynamics, and augmented protection against environmental factors such as moisture, UV radiation, and thermal stress. The review also discusses the diverse materials and fabrication methods employed in the development of nanocomposite coatings, highlighting their unique properties and practical applications with multifunctional benefits. Moreover, this comprehensive review explores recent advances in the field, encompassing the integration of novel nanomaterials, smart coatings, and multifunctional strategies that enable solar cells to simultaneously exhibit multiple desirable traits. Besides, the review offers insights into future prospects and challenges, presenting a roadmap for harnessing the full potential of nanocomposite coatings in solar cell technology. By unlocking the multifunctional advantages of nanocomposite coatings, this review aims to catalyze further research and innovation, ultimately advancing the prospects of sustainable and efficient solar energy generation.

A novel self-healing coating with mechanically-triggered self-reporting properties: Color and fluorescence dual damage indications

Smart coatings with self-reporting and self-healing functions are essential to prolong their service life. In this work, a novel strategy was proposed to fabricate a dual-function coating with both mechanically triggered self-reporting ability and shape memory effect activated self-healing function. Polyurethane/poly-(urea-formaldehyde) microcapsules containing 2′,7′-dichlorofluorescein (DCF) were incorporated into the shape memory epoxy polymer (SMEP) coatings, and the molar ratios of curing agent and epoxy monomer were adjusted to modify the residual amino groups in the coating so as to strengthen both the self-reporting and self-healing performances. Once the coating was mechanically damaged, DCF would release from the ruptured DCF@PU/UF microcapsules and react with the residual amino groups in the coating to illustrate prominent red color. Even with a topcoat of polyurethane varnish or black paint, yellow fluorescence signals of DCF could be facilely observed upon ultraviolet light irradiation. For the self-healing performance, the high mobility of polymer networks endowed the coating with shape memory effect to recover the original shape and the barrier property. This strategy exhibits excellent potential to prolong the service lifetime of smart coatings.

Double Photocrosslinked Responsive Hydrogels Based on Hydroxypropyl Guar.

Double crosslinked hydrogels based on a biodegradable polymer were prepared by photocopolymerization of methacrylated hydroxypropyl guar (HPG-MA) and 3-acrylamidophenylboronic acid. Along with irreversible strong covalent crosslinks by methacrylic groups, these hydrogels contained labile boronate crosslinks formed as a result of the interaction of boronic acid with cis-diol moieties of HPG. These hydrogels demonstrated higher elasticity than HPG-MA hydrogels with only irreversible covalent crosslinks. Labile boronate crosslinks not only strengthened the hydrogels but also imparted to them pronounced responsive properties. It was demonstrated that the mechanical properties, the swelling behavior, as well as the uptake and release of some substances from the double crosslinked hydrogel were pH controlled. For instance, the hydrogels could release cationic disinfectant at a rate regulated by pH. Such photocrosslinkable in situ forming hydrogels are very promising for the production of smart coatings that release targeted substances at the desired rate.

Radiative thermal coats for passive temperature management

Radiative thermal management has advantages in precision electronic instruments owing to zero-energy consumption and high integration convenience. The possibility to acquire high-performance thermal stability through engineering the surface emissivity of object has been investigated. Herein, developing a smart coat was reported that could passively maintain the temperature of objects (silicon chips) in a predefined thermal window to avoid overheating or overcooling in vacuum. The technique implements using a multilayer structure incorporating a 30 nm thick VO2 phase-change medium having a 300% modulation depth for emissivity under varying temperatures. In the experiment, a 1.78 μm thick smart coat could raise the temperature stability of a regular coat by ∼2.0 times. The potential of the work remains in thermal radiation for smart temperature management especially in space applications.

Thermochromic Printable and Multicolor Polymeric Composite Based on Hybrid Organic-Inorganic Perovskite.

Hybrid organic-inorganic perovskites (PVKs) are among the most promising materials for optoelectronic applications thanks to their outstanding photophysical properties and easy synthesis. Herein, a new PVK-based thermochromic composite is demonstrated. It can reversibly switch from a transparent state (transmittance > 80%) at room temperature to a colored state (transmittance < 10%) at high temperature, with very fast kinetics, taking only a few seconds to go from the bleached to the colored state (and vice versa). X-ray diffraction, Fourier-transform infrared spectroscopy, differential scanning calometry, rheological, and optical measurements carried out during heating/cooling cycles reveal that thermochromism in the material is based on a reversible process of PVK disassembly/assembly mediated by intercalating polymeric chains, through the formation and breaking of hydrogen bonds between polymer and perovskite. Therefore, differently from other thermochromic perovskites, that generally work with the adsorption/desorption of volatile molecules, the system is able to perform several heating/cooling cycles regardless of environmental conditions. The color and transition temperature (from 70 to 120°C) can be tuned depending on the type of perovskite. Moreover, this thermochromic material is printable and can be deposited by cheap techniques, paving the way for a new class of smart coatings with an unprecedented range of colors.

Numerical analysis for 3D time-dependent Sutterby nanofluid flow capturing features of variable thermal conductivity and heat sink-source aspects

Presently, due to its extraordinary mechanical, thermal, electrical and biomedical facets nanofluids deliver several prospects to exaggerate the propensity of isothermal systems by augmenting the conductivity features of the host fluids. In various areas of the energy partition, nanoparticles show a remarkable measure in energy storage, energy variation, and energy convertible, i.e. thermoelectric plans, petroleum cells, supercapacitors, stellar cells, rechargeable batteries, light-radiating diode and carbon-based light-radiating diode, smart coatings. In this current conversation, we anticipated an unsteady 3D flow of the Sutterby nanofluid consequence of a bidirectional extended surface. To envision the thermophoresis and Brownian motion properties in Sutterby’s nanofluid, the Buongiorno association is utilized in an additional refined technique. Variable thermal conductivity with heat source/sink property occurred deliberated considering heat transmission techniques. The appropriate transformation is applied for transposing the PDEs into nonlinear ODEs. For numerical results, the bvp4c programmed is prerequisite for elucidating the subsequent Ordinary differential equations. The distinct performance of the Sutterby nanofluid temperature and the concentration field are designated and discussed in the physical parameter’s aspect. It is clear that the temperature of the Sutterby fluid decreases with respect to the ratio of stretching rates parameter and similar developments are observed for the thermophoresis and Brownian motion parameters. Furthermore, the concentration profile declines for sophisticated estimates of the Lewis number and thermophoresis parameters.

Nonconductive layered hexagonal boron nitride preparation via a co-exfoliation strategy and nanohybrid coating construction for corrosion protection

Hexagonal boron nitride (h-BN), an analogue of graphene with similar layered structure, is considered as the promising material in place of graphene for application as nanofiller into polymeric matrices to develop the smart coatings for corrosion protection of metallic substrates, owing to its mechanical robustness and thermal stability together with unique electrically insulating nature. In this work, on the basis of a co-exfoliation strategy, h-BN were exfoliated by riboflavin sodium phosphate (FMN) intercalator, assisted with ball-milling to obtain few-layered nanosheets with improved water-dispersibility as well as improve their compatibility with waterborne epoxy matrix. The results from electrochemical measurement and corrosion product analysis indicate that the incorporation of only 1.0 wt% FMN-exfoliated h-BN (h-BN@FMN nanohybrids) content into waterborne epoxy matrix can realize the optimized long-term corrosion resistance of composite coatings in 3.5 wt% NaCl solution. The two-dimensional morphology and impenetrability of h-BN, together with the compatibility of waterborne epoxy system from the bridge role of FMN molecules to act as a physical barrier against corrosive species (i.e., H2O, Cl− and O2), are the main reasons behind the prominent anticorrosion performance of our composite coating.

Polyelectrolyte-based antifouling and pH-responsive multilayer coatings for reverse osmosis membrane

Membrane fouling, the accumulation of material on the membrane surface, has been a challenge that limits the application of reverse osmosis technology. Ordinary cleaning processes do not remove contaminants from the membrane surface. To effectively clean a membrane, we fabricated a sacrificial multilayer polyelectrolyte coating based on a layer-by-layer assembly approach using chitosan (CS) and tannic acid (TA) on the membrane surface. The CS/TA coated membranes represent a superior permeance flux of 64 L m−2 h−1 with a clear NaCl rejection of 98.89 %. Meanwhile, the membrane surface hydrophilicity was enhanced due to the abundant amino and hydroxyl groups, which shows superior anti-fouling properties against proteins, polysaccharides, and surfactant. Moreover, the coatings were unstable, which would decompose at pH 8.5. The degradation endows the coated membranes approving long-term anti-fouling performance, which the permeance recovery reaching up to 85 %. Constructing pH-responsive smart coatings provides a promising route to address membrane fouling. It can be upscaled in numerous practical applications like sensors, medical devices, and drug delivery.

High-quality VO2 films synthesized on polymer substrates using room-temperature pulsed laser deposition and annealing

With the growing trend towards portable and adaptable devices in various fields, the demand for flexible electronics and coatings utilizing phase transition materials like VO2 as a functional layer is rising. However, depositing high-quality crystalline VO2 films directly onto polymer substrates remains challenging due to the thermosensitivity of such materials being barely compatible with usual VO2 deposition methods. In this study, we present a simple method for directly growing VO2 on Kapton substrates. VOx films were first deposited onto the Kapton substrate at room temperature using pulsed laser deposition and subsequently annealed in an oxygen atmosphere at 390 °C. The electrical and optical properties of the VO2/Kapton samples with different film thicknesses were investigated. The 200 nm-thick vanadium dioxide films exhibit the best resistivity contrast with 3.1 orders of magnitude (OOM), while the 50 nm-thick films show the best transmittance change of 54 % at 2500 nm. The switching performances are comparable or even superior to those achieved previously using more complicated synthesis processes such as film transfer, introduction of buffer layers, and ink injection. Additionally, by coupling W elemental doping and thin film strain, we successfully tuned the VO2 transition temperature to room temperature with a dopant concentration of only 1.1 at.% while maintaining a high electrical contrast (2 OOM). The impressive electrical and optical transition performance of the VO2/Kapton samples, combined with their tunable transition temperature, makes them promising candidates for flexible electronic devices and thermochromic smart coatings.

Smart Biomaterials: An Evolving Paradigm in Dentistry.

According to definition and general agreement, smart materials have properties that can be altered in a controlled fashion by stimuli including stress, temperature, moisture, pH, and electric or magnetic fields. Various recent materials in materials science are in working order, meaning they must achieve their tasks and should go through intentional modification. Smart materials change one or more of their characteristics in response to inputs. They can be called as responsive materials. As these materials have been available for so long, they are used for a wide range of purposes. These qualities have useful applications in many different industries, including dentistry. Zirconia, shape-memory alloys, and SmartSeal obturation system (Prosmart-DRFP Ltd., Stamford, United Kingdom) are a few examples of dental materials with intelligent behavior. The creation of novel materials is a major trend in materials science. These materials might make it possible to develop cutting-edge dental therapies with vastly improved clinical results. This article reviews the following: nickel-titanium smart alloy, smart composites, self-healing composites, smart ceramics, glass ionomer cement as a smart material, SmartSeal obturation system, and smart coatings for dental implants. We can better understand these biosmart materials with the aid of this review. The development of these newer and superior smart materials makes the outcome of the treatment far better for both the operator and the patient.

Self-Healing Antimicrobial Silicones-Mechanisms and Applications.

Organosilicon polymers (silicones) are an important part of material chemistry and a well-established commercial product segment with a wide range of applications. Silicones are of enduring interest due to their unique properties and utility. Recently, new application areas for silicone-based materials have emerged, such as stretchable electronics, wearable stress sensors, smart coatings, and soft robotics. For this reason, research interest over the past decade has been directed towards new methods of crosslinking and increasing the mechanical strength of polyorganosiloxanes. The introduction of self-healing mechanisms may be a promising alternative for such high-value materials. This approach has gained both growing research interest and a rapidly expanding range of applications. Inherent extrinsic and intrinsic self-healing methods have been used in the self-healing of silicones and have resulted in significant advances in polymer composites and coatings, including multicomponent systems. In this review, we present a summary of research work dedicated to the synthesis and applications of self-healing hybrid materials containing polysiloxane segments, with a focus on antimicrobial and antifouling coatings.

Cytocompatibility, antibacterial, and corrosion properties of chitosan/polymethacrylates and chitosan/poly(4-vinylpyridine) smart coatings, electrophoretically deposited on nanosilver-decorated titania nanotubes.

The development of novel implants subjected to surface modification to achieve high osteointegration properties at simultaneous antimicrobial activity is a highly current problem. This study involved different surface treatments of titanium surface, mainly by electrochemical oxidation to produce a nanotubular oxide layer (TNTs), a subsequent electrochemical reduction of silver nitrate and decoration of a nanotubular surface with silver nanoparticles (AgNPs), and finally electrophoretic deposition (EPD) of a composite of chitosan (CS) and either polymethacrylate-based copolymer Eudragit E 100 (EE100) or poly(4-vinylpyridine) (P4VP) coating. The effects of each stage of this multi-step modification were examined in terms of morphology, roughness, wettability, corrosion resistance, coating-substrate adhesion, antibacterial properties, and osteoblast cell adhesion and proliferation. The results showed that the titanium surface formed nanotubes (inner diameter of 97 ± 12 nm, length of 342 ± 36 nm) subsequently covered with silver nanoparticles (with a diameter of 88 ± 8 nm). Further, the silver-decorated nanotubes were tightly coated with biopolymer films. Most of the applied modifications increased both the roughness and the surface contact angle of the samples. The deposition of biopolymer coatings resulted in reduced burst release of silver. The coated samples revealed potent antimicrobial activity against both Gram-positive and Gram-negative bacteria. Total elimination (99.9%) of E. coli was recorded for a sample with CS/P4VP coating. Cytotoxicity results using hFOB 1.19, a human osteoblast cell line, showed that after 3 days the tested modifications did not affect the cellular growth according to the titanium control. The proposed innovative multilayer antibacterial coatings can be successful for titanium implants as effective postoperative anti-inflammation protection.