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Photonic‐ionic skins (PI‐skins) featuring multi‐signal synergistic outputs exhibit fascinating interactive sensing potential in flexible iononics. However, the existing ones are susceptible to irreversible damage in usage due to their poor toughness and deficiency in self‐healing. Herein, a novel tough mechanochromic PI‐skin is ingeniously constructed, from both molecular engineering and nanostructural engineering perspectives, via integrating the ordered photonic array and robust metal‐imidazole cross‐linked network. The PI‐skin displays synchronous structural color variation and sensitive electrical response under strain. Notably, the synergy of dense physical cross‐linking network and microphase‐separation structure achieved by strong metal‐imidazole coordination greatly promotes energy dissipation. PI‐skin possesses a combination of exceptional properties, including high fracture strength (8.22 MPa), remarkable toughness (10.23 MJ m−3), and robust adhesion behavior (2.30 MPa). Furthermore, favorable self‐healing capability at room temperature is realized thanks to the dynamic topological rearrangement of metal‐imidazole coordination. The PI‐skin demonstrates promising uses as a visually interactive wearable device for human motion monitoring and remote communication. This work not only broadens design considerations for the development of high‐performance artificial skins but also offers a general optical platform for high‐level interactive wearable devices. [ABSTRACT FROM AUTHOR]

Assessment of the local strain/stress changes of adhesives is highly desirable for their service to avoid premature failure. However, monitoring local strain/stress variations in adhesives in practical settings remains challenging, especially in aqueous media. Here, an underwater structurally‐colored adhesive for visualized local strain/stress monitoring in aqueous media is reported. The structurally‐colored adhesive is obtained by shearing composites of poly(butyl acrylate‐co‐acrylic acid) copolymer and carboxylated polystyrene colloidal particles. The resultant structurally‐colored adhesive exhibits underwater adhesive strength (i.e., 238 kPa for stainless steel substrates) to various substrates (e.g., metals and plastics) thanks to hydrophobic segments and carboxyl groups. Notably, they can shift color in response to external force, enabling real‐time visual monitoring of localized strain/stress changes. As a proof of concept, the structurally‐colored adhesive can be used to seal a leaking hole on a bottle or tube, and it can precisely visualize the localized pressure distribution, providing critical information on the adhesion performance and the local pressure. These distinctive properties make the structurally‐colored adhesive suitable for application in wet environments as a real‐time visual pressure tracking device. [ABSTRACT FROM AUTHOR]

The ability to actively control broadband light absorption and reflection ranging from deep‐ultraviolet (DUV) to near‐infrared (NIR), is crucial for various optical and optoelectronic applications. Herein, a novel type of ultrathin, lithography‐free, and broadband aperiodic thin‐film metamaterial coatings (metacoatings) is inverse‐designed from DUV to NIR (190–1700 nm), which is composed of a series of deeply subwavelength tungsten oxide layers with graded refractive index profiles (by varying the deposited Ar gas pressures from 0.1 to 3.0 Pa) above an opaque aluminum layer. Experimental results show that these proposed aperiodic metacoatings can realize a transition from broadband strong absorption (as‐deposited state) to high reflection (annealed state) from visible (VIS) to NIR (400–1700 nm), through thermal annealing techniques. The aperiodic metacoatings have an overall thickness of just ≈200 nm, with angle‐insensitive up to 70° as well as are polarization‐independent. Furthermore, vivid structural colors can be generated by rearranging the aperiodic tungsten oxide layers and finally employed in color display applications. These aperiodic metacoatings offer a very promising platform for many applications such as broadband photodetectors, thermophotovoltaics, information encryption devices, etc. [ABSTRACT FROM AUTHOR]

Fabricating photonic crystals (PCs) with dynamic multi‐stimuli‐responsive structural colors, recordable colors, and self‐healable properties is significant for their emerging applications, yet remains a big challenge. Here, an all‐in‐one multifunctional PC (MFPC) film with outstanding mechanochromic, thermochromic, solvatochromic, color/shape‐recordable, self‐healable, and adhesive functions is designed and prepared by simply non‐close‐assembling silica particles into the unique 2‐[[(Butylamino)carbonyl]oxy]ethyl acrylate (BCOEA) followed by photopolymerization. The success is mainly due to the rational combination of non‐close‐packing structures and BCOEA's characteristics, including its urethane groups with numerous sacrificial hydrogen bonds, temperature‐dependent refractive index, swellable and deformable polymer network, as well as low glass‐transition temperature. The MFPC's hue and color saturation can be reversibly and dynamically modulated by strain/pressure/solvents and temperature, respectively, thereby realizing visually and spectrally sensing these stimuli. More interestingly, the color‐responsiveness combined with other functions endows MFPCs with fascinating emerging applications, including multilayer optical filters, inkless printing, reconfigurable multicolor patterns, stretching‐based anti‐counterfeiting, etc. This work offers a new perspective for designing next‐generation smart photonic materials and will facilitate their all‐round applications. [ABSTRACT FROM AUTHOR]

Inspired by stimuli‐responsive creatures in nature, developing devices with synergistic color change and deformation will be of great value for realizing the adaptive variants. Yet, integrating adaptive color variation and deformation into a single device remains elusive. Herein, an intriguing electrochromic actuator based on MXene/WO3 bilayer film is developed with Fabry−Pérot (F–P) microcavity, which successfully integrates both functions of reversible deformation and vivid color variations into the same device. Upon applying a small electric field, the ion intercalation/de‐intercalation can synchronously alter the stress distribution and optical absorption of MXene/WO3, resulting in the dual response of electrochromic phenomenon and ultra‐fast deformation with a maximum angle of 95° within 10 s. Moreover, the F–P microcavity architecture with the physical light interaction additionally endows the bilayer film with a bright color gamut and high color tunability (yellow–green, purple, pink, blue, etc.). Furthermore, an asymmetric soft actuator based on MXene/WO3 bilayer film is assembled, which displays robust grasping ability and excellent cycling stability up to 1000 cycles. These findings may open new opportunities for somatosensory soft robots and next‐generation intelligent robots. [ABSTRACT FROM AUTHOR]

[Display omitted] Optical information encryption with high encoding capacities can significantly boost the security level of anti-counterfeiting in the scenario of guaranteeing the authenticity of a wide scope of common and luxury goods. In this work, a novel counterfeiting material with high-degree complexity is fabricated by microencapsulating cholesteric liquid crystals and triplet–triplet annihilation upconversion fluorophores to integrate structural coloration with fluorescence and upconversion photoluminescence. Moreover, the multimode security ink presents tailorable optical behaviors and programmable abilities on flexible substrates by various printing techniques, which offers distinct information encryption under different optical modes. The advanced strategy provides a practical versatile platform for high-secure-level multimode optical inks with largely enhanced encoding capacities, programmability, printability, and cost-effectiveness, which manifests enormous potentials for information encryption and anti-counterfeiting technology. [ABSTRACT FROM AUTHOR]

Photonic crystals enable further manipulation of light at the nanometer scale, and the preparation of photonic crystal inks becomes a novel approach in achieving multifunctional and customizable light manipulation. The unique physical structure of photonic crystals exhibits special structural colors, which find wide applications in fields such as displays, sensors, information storage and anti‐counterfeiting measures, printing, and biomedicine. Compared to traditional dye‐based inks containing chemical pigments, photonic crystal inks not only maintain vibrant colors for longer durations but also significantly reduce environmental harm. This article introduces the basic characteristics of photonic crystal inks, summarizes recent synthetic methods of some inks, and finally concludes with an overview and prospects of the applications and development directions of photonic crystal inks. [ABSTRACT FROM AUTHOR]

Amid the proliferation of counterfeit and shoddy products, it is imperative to develop efficient and reliable encryption and anticounterfeiting technologies. Here, we present a two-level information security system with encryption and anticounterfeiting functions that can exhibit multioptical states. A phase transition material of P-(N-isopropylacrylamide) (PNIPAM) film with a nanometer-sized inverse quasi-amorphous array (PIQA) is prepared using a sacrificial templating method. In the dry state, the PIQA film is highly transparent due to the collapse of internal pores, effectively concealing any preset information. When immersed in water, the nanometer-sized quasi-amorphous array of the PIQA film rapidly recovers, producing vibrant structural colors and revealing encrypted information. By simple increase of the temperature, the PIQA film undergoes a vibrant color change. This occurs because as the temperature increases, the PIQA film undergoes a phase transition, with its volume first expanding and then contracting. Correspondingly, the reflection peak wavelength of the PIQA film undergoes a red shift, followed by a blue shift. When the temperature exceeds 35 °C, phase separation occurs in the PIQA film, resulting in a white color. This feature for multiple color transformations solely through temperature increase serves as an authentication for accurate information. The reversible switching of multioptical states demonstrates great potential and advantages in the field of information security. [ABSTRACT FROM AUTHOR]

Hexamethylenediamine (HMDA), as an important chemical intermediate, plays a crucial role in the production of nylon-66 and finds widespread applications in various fields such as synthetic fibers, textile manufacturing, fertilizers, pharmaceuticals, electronics, and polymer materials. Addressing the efficient detection of HMDA pollution in water, this study successfully prepared a photonic crystal sensor sensitive to HMDA by altering the ratio of functional monomers to crosslinker. The sensor, referred to as inverse opal polymeric photonic crystals (IOPPCs), exhibited optimal responsive performance when the functional monomer was acrylic acid (AA) and the ratio of functional monomer to crosslinker was 5:0.5. Research results indicate that as the HMDA concentration increased from 1 mM to 10 mM, the redshift of the reflection of IOPPCs increased from 3 nm to 140 nm, accompanied by a color change from green to red, enabling visual semi-quantitative detection. Additionally, the prepared IOPPCs demonstrated good anti-interference property and reusability. [ABSTRACT FROM AUTHOR]

In recent years, structural color has attracted more and more attention due to its bright color, eco-friendliness, et al. In this study, SiO2 microspheres with different diameters were prepared by multi-step addition of silicon source. Vertical self-assembly was used to construct long-range ordered photonic crystals, and spin-coating assembly methods was used for short-range ordered amorphous photonic crystals. The influence of process parameters on the assembly quality was explored. Results show that the structural color shifts to red with the increase of SiO2 particle size, and vice versa. 0.5wt% SiO2-ethanol suspension was vertically assembled at 60 °C, and the structural color was angle-dependent. Amorphous photonic crystals were assembled with 2 wt% SiO2-ethanol/ethylene glycol (mass ratio 8.5:1.5) suspension spinning at 3 000 rpm. The structural color was not angle-dependent, and the color saturation was lower than that of the former. This research provides a simple and effective method for assembling high-quality SiO2 photonic crystals and amorphous photonic crystal films, which shows great potential in decoration, anti-counterfeiting, automotive coatings, textile,et al. [ABSTRACT FROM AUTHOR]

ZrN–SiO2 core–shell particles were prepared, where the ZrN core nanoparticles and SiO2 shell were designed to exhibit localized surface plasmon resonances (LSPRs) and structural coloring. The heating of ZrO2 nanoparticles with Mg3N2 under a nitrogen gas flow produced ZrN nanoparticles with a diameter in the range of 10–20 nm. The dispersion of ZrN nanoparticles in water exhibited an absorption maximum at approximately 700 nm owing to LSPRs. An SiO2 shell was formed on the ZrN nanoparticles using a sol–gel process. Scanning transmission electron microscopy confirmed the formation of ZrN–SiO2 core–shell particles containing ZrN particles with a diameter of approximately 10 nm. The SiO2 shell thickness was controlled by varying the reaction time to form SiO2. The use of particles as a structural component of a structural color material owing to the high uniformity of the size of obtained core–shell particles was investigated. The obtained ZrN–SiO2 core–shell particles were arrayed on a glass substrate using a layer‐by‐layer method. The particle‐stacked film of the ZrN–SiO2 core–shell particles exhibited the maximum reflection depending on the particle size of the SiO2 shell. [ABSTRACT FROM AUTHOR]

A super‐black wood with low reflectivity in the UV/Vis range is created by plasma modifying basswood surfaces. Here the super‐black wood is characterized, the process used to make it is described and its possible practical uses are discussed. Wood samples are exposed to oxygen glow‐discharge plasma. Transverse surfaces exposed to high‐energy plasma have a deep‐black velvety appearance. The reflectance of these surfaces is measured and compared with those of commercial super‐black materials. The reflectivity of samples over a narrower wavelength range is measured with a spectrophotometer and converted into lightness values. The microstructure and surface chemistry of super‐black wood are examined using SEM/X‐ray micro‐CT and FTIR spectroscopy, respectively. Transverse basswood samples modified with high‐energy plasma have reflectivity averaging 0.68% (300–700 nm). The super‐black color of plasma‐modified wood is retained when it is coated with gold/vanadium alloy indicating structural coloration. Plasma creates a low density, lignin‐enriched surface with deep pits, columns and tangled fibrils; features also found in synthetic super‐black materials. In conclusion, this method of creating a super‐black material by plasma‐modification of basswood does not require a lithography pre‐step, generates no liquid waste and, as is demonstrated here, can be used to prototype luxury consumer products. [ABSTRACT FROM AUTHOR]

Photonic crystals are a new class of optical microstructure materials characterized by a dielectric constant that varies periodically with space and features a photonic bandgap. Inspired by natural photonic crystals such as butterfly scales, a series of artificial photonic crystals are developed for use in integrated photonic platforms, biosensing, communication, and other fields. Among them, colloidal photonic crystals (CPCs) have gained widespread attention due to their excellent optical properties and advantages, such as ease of preparation and functionalization. This work reviews the classification and self‐assembly principles of CPCs, details some of the latest biomedical applications of large‐area, high‐quality CPCs prepared using advanced self‐assembly methods, summarizes the existing challenges in CPC construction and application, and anticipates future development directions and optimization strategy. With further advancements, CPCs are expected to play a more critical role in biosensors, drug delivery, cell research, and other fields, bringing significant benefits to biomedical research and clinical practice. [ABSTRACT FROM AUTHOR]

Biomimetic optical devices based on cellulose nanocrystals with tunable structural colors have received significant attention recently. However, the limited ability to control multicolor separation beyond simple single‐color modulation restricts its practical applications. Here, a diversified multicolor separation strategy for the cholesteric phase cellulose composite (CPCC) is presented. The CPCC is prepared by integrating a high‐concentration self‐assembled hydroxypropyl cellulose with a cross‐linked poly(acrylic acid‐acrylamide) (P(AA‐AM)) network. By adjusting the cross‐linking degree of P(AA‐AM) in CPCC, Thermally induced multicolor separation is achieved from a homochromatic state at room temperature to multicolor patterned display at elevated temperatures. Furthermore, by utilizing the electric heating effect of conductive carbon oil, the multicolor separation under low voltage is achieved, and based on this, pixelated electro‐thermochromic displays are developed. Additionally, magneto‐thermal multicolor separation induced by introducing FeNi3 nanoparticles is investigated with efficient magnetic induction heating ability into CPCC. The multicolor separation effect is further improved by pixelated distribution of FeNi3 nanoparticles and adjusting the concentration of FeNi3 in each pixel. Finally, thermochromism, electro‐thermochromic, and magneto‐thermochromic functionalities are integrated into the CPCC, achieving advanced multilevel information encryption. This multilevel approach of controlling multicolor separation significantly enhances the functionality of nanocellulose in various potential photonic applications. [ABSTRACT FROM AUTHOR]

Structural dyeing has attracted much attention due to its advantages such as environmental friendliness, vivid color, and resistance to fading. Herein, we propose an alternative strategy for fabric coloring based on Cu2O microspheres. The strong Mie scattering effect of Cu2O microspheres enables the creation of vibrant structural colors on fabric surfaces. These colors are visually striking and can potentially be adjusted by tuning the diameter of the microspheres. Importantly, the Cu2O spheres were firmly bonded to the fabrics by using the industrial adhesive PDMS, and the Cu2O structural color fabrics exhibited excellent color fastness to washing, rubbing, and bending. Cu2O structural color fabrics also demonstrated excellent antimicrobial properties against bacteria such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The bactericidal rates of Cu2O structural color textiles after washing for E. coli and S. aureus reached 92.40% and 94.53%, respectively. This innovative approach not only addresses environmental concerns associated with traditional dyeing processes but also enhances fabric properties by introducing vibrant structural colors and antimicrobial functionality. [ABSTRACT FROM AUTHOR]

Photonic crystals (PC) with structural colors have been used in various sensors or indicators given that they change the colors upon mechanical deformation. However, the color also changes according to the incident or viewing angle, presenting a challenge when the structural color serves as the practical sensor or indicator. Therefore, it is necessary to compensate for this color variation caused by the incident or viewing angle. This study presents devices in which strain-sensitive photonic crystals (SSPCs) and strain-insensitive crystals are fabricated together. The photonic crystals were fabricated by the self-assembly of nanoparticles and the deposition of a thin metallic film, after which they were transferred onto flexible and adhesive tape so that the devices, i.e., the sensors and indicators, could be fabricated. When the nanoparticles were in a close-packed arrangement, the thin film formed into a continuous layer upon a monolayer of the nanoparticles. Accordingly, the lattice constant of the PC did not change while the device were deformed, resulting in strain-insensitive photonic crystals (SIPCs). Meanwhile, when the nanoparticles were not in a close-packed arrangement, as realized by deep reactive ion etching, the thin film formed into separate layers on the individual nanoparticles. The lattice constant of the PC varied in this case when the device were deformed, resulting in strain-sensitive photonic crystals. The devices consist of both types of photonic crystals such that the colors from each PC could be compared to each other, enabling angle-compensating characteristics. In this way, the colors can be used as effective signals of mechanical strain or as chemical liquids at arbitrary angles. They can also be used as an anticounterfeiting stamp. This study thus introduces a fabrication method that therefore enables a choice between strain-sensitive and strain-insensitive photonic crystals. [ABSTRACT FROM AUTHOR]

[Display omitted] Thermally-induced in-situ gelation of polymers and nanogels is of significant importance for injectable non-invasive tissue engineering and delivery systems of drug delivery system. In this study, we for the first time demonstrated that the interpenetrating (IPN) nanogel with two networks of poly (N-isopropylacrylamide) (PNIPAM) and poly (N-Acryloyl- l -phenylalanine) (PAphe) underwent a reversible temperature-triggered sol-gel transition and formed a structural color gel above the phase transition temperature (Tp). Dynamic light scattering (DLS) studies confirmed that the Tp of IPN nanogels are the same as that of PNIPAM, independent of Aphe content of the IPN nanogels at pH of 6.5 ∼ 7.4. The rheological and optical properties of IPN nanogels during sol-gel transition were studied by rheometer and optical fiber spectroscopy. The results showed that the gelation time of the hydrogel photonic crystals assembled by IPN nanogel was affected by temperature, PAphe composition, concentration, and sequence of interpenetration. As the temperature rose above the Tp, the Bragg reflection peak of IPN nanogels exhibited blue shift due to the shrinkage of IPN nanogels. In addition, these colored IPN nanogels demonstrated good injectability and had no obvious cytotoxicity. These IPN nanogels will open an avenue to the preparation and thermally-induced in-situ gelation of novel NIPAM-based nanogel system. [ABSTRACT FROM AUTHOR]

Traditional photonic crystal films are becoming increasingly popular in the fields of smart sensing and optical devices due to their high brightness level, but at the same time there is a lack of color saturation and angle dependence, which seriously affects the application of structural color in visual response and display fields. Here, the optical performance of the photonic crystal films was improved by doping a certain amount of carbon black and carbon quantum dots during the film preparation process. Doping carbon quantum dots can effectively compensate for the optical brightness loss caused by the introduction of black substances by utilizing their self-sustained photoluminescence behavior that matches the photonic bandgap. In addition, the introduction of black nanoparticles can effectively enhance surface-resonant scattering, resulting in low angle-dependent structural colors, further expanding the application of structural color in optical display fields. [ABSTRACT FROM AUTHOR]

[Display omitted] • Automatic color-tunable actuator is from combining photonic crystals with hygroscopic film. • The actuator self-flickers under the natural humidity gradient environment. • The actuator shows continuous upward-downward bending motion and autonomous color switching. • This work offers a new strategy to develop an automatic intelligent actuator. Color-tunable actuators with motion and color-changing functions have attracted considerable attention in recent years, yet it remains a challenge to achieve the autonomous regulation of motion and color. Inspired by Apatura ilia butterfly with dynamic structural color and Pelargonium carnosum plant with moisture responsive bilayer structure, an automatic color-tunable actuator is developed by integrating photonic crystals layer and hygroscopic layer. Taking advantage of the asymmetric hygroscopicity between two layers and the angle-dependent structural color of photonic crystals, this actuator can continuously self-flicker in humid environment by visual switching in structural color due to automated cyclic motion. The actuator is assembled into the self-flapping biomimetic butterfly with switchable color and the self-reporting information array with dynamic visual display, demonstrating its autoregulatory motion and color. This work provides a new strategy for developing automatic color-tunable actuator and suggests its potential in the intelligent robot and optical display. [ABSTRACT FROM AUTHOR]

[Display omitted] Photonic ionogels with dual electrical and optical output have been intensively studied. However, tunable temperature-responsive photonic ionogel assembled by thermosensitive nanogels has not been studied yet. Herein, an innovative approach to fabricate photonic ionogels has been developed for smart wearable devices with tunable temperature sensitivity and structural color. Firstly, poly(isopropylacrylamide-r-phenylmaleanilic acid) P(NIPAm-r-NPMA) nanogels self-assemble into photonic crystals in 2-hydroxyethyl acrylate (HEA), water, and the ionic liquid of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate. And then robust photonic ionogels are developed through a polymerization of 2-hydroxyethyl acrylate crosslinked by poly(ethylene glycol) diacrylate (PEGDA). The incorporation of the ionic liquid, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, enhances the mechanical strength of photonic ionogels and tunes the temperature-sensitivity of the ionogels, making them adaptable to various environmental conditions. The findings demonstrate that these ionogels can serve dual functions in smart wearable devices, combining electrical and optical signal outputs due to the conductivity of the ionic liquid and structural color from the nanogel assembly. The resultant photonic ionogels exhibit exceptional substrate adhesion, mechanical stability, and fast resilience. More significantly, the nanogels within these ionogels serve as the building blocks of photonic crystals (PCs) endow with angle-independent coloration and enhance stretchability beyond 200 %, while the stretchability of the ionogles without the nanogels is only about 100 %. Our photonic ionogels with tunable temperature-sensitivity and dual outputs will open an avenue to the development of the innovative smart wearable devices. [ABSTRACT FROM AUTHOR]

Optical multilayer thin film structures have been widely used in numerous photonic applications. However, existing inverse design methods have many drawbacks because they either fail to quickly adapt to different design targets, or are difficult to suit for different types of structures, e.g., designing for different materials at each layer. These methods also cannot accommodate versatile design situations under different angles and polarizations. In addition, how to benefit practical fabrications and manufacturing has not been extensively considered yet. In this work, we introduce OptoGPT (Opto Generative Pretrained Transformer), a decoder-only transformer, to solve all these drawbacks and issues simultaneously.

Highlights Derived from silica photonic crystals, inverse opal microspheres have a regularly connected porous structure and inherit structural color properties. Combined with the stable scaffold and the photothermal phase-transition of the secondary filling material, the inverse opal composite microspheres are endowed with self-healing properties and the ability for controllable drug release. Inverse opal microspheres were significantly treated for diabetic wound, via promoting tissue regeneration, collagen deposition and angiogenesis. Meanwhile, the release of drugs could be monitored by the structural color characteristic.

Structural color, arising from the interaction between nanostructures and light, has experienced rapid development in recent years. However, high-order Mie resonances in dielectric materials often induce unnecessary sub-peaks, particularly at shorter wavelengths, reducing the vibrancy of colors. To address this, we have developed a multilayer dielectric metasurface based on silicon-rich silicon nitride (SRN), achieving expanded color gamut through precise refractive index matching and suppression of high-order resonances. This strategy introduces more design dimensions and can reduce the complexity of material deposition. It enables the generation of vibrant colors in a 3 × 3 array, with a resolution of approximately 25,400 dpi, demonstrating its potential applications in displays.

The self‐assembled cellulose nanocrystal (CNC) film has a left‐handed layered structure, which makes the reflection of right‐handed circularly polarized (CP) light a challenge. Herein, a nematic phase layer is designed and inserted into the chiral organization, to work as a half‐wave retarder and make the ambidextrous CP light reflection. The maximum reflectivity exceeds 80%, which breaks the 50% limitations of single‐direction light reflection and is the current maximum in all the reported CNC‐based films. This “sandwich‐like” structure displays different optical properties on both sides, displayed as the chromatism and the inversion of the circular dichroism signals. The dual CP light reflection and direction‐dependent optical phenomena are reserved in the synthesized circularly polarized luminescence (CPL) film, with the dissymmetry factor (glum) of −0.4245. However, this luminescent intensity and single‐direction emission are not enough in advanced optical systems. This work designs a triple CPL amplification path and develops the handedness inversion strategy, with the glum of −1.0551 and 0.4082. Then, the dual‐directional CPL emission films are designed, where the chiral optics can be switched on‐demand. Finally, the photonic crystal films are applied in the anti‐counterfeit and chiral superstructure induction. [ABSTRACT FROM AUTHOR]

This work utilizes the self‐assembled cellulose nanocrystals (CNCs) as the host chiral template and fabricates a circularly polarized luminescence (CPL) film. By manipulating the photonic bandgap, the synthesized film integrates a strong CPL signal and superior mechanical flexibility. Without losing the CPL activity, the ultimate strain of 19% has exceeded most CNC‐based chiral luminescent assemblies, which enables them candidates in the optical sensor and wearable device. Meanwhile, the film has a humidity‐stimulus CPL response, with the dissymmetry factor (glum) close to 0.51. This responsive process is reversible and the optical properties can recover upon drying. Next, by manipulating the optical pathway, this work achieves on‐demand CPL direction control and meets the considerable intensity of reversed optical signals (glum: ‐0.35), avoiding the structure disruption and direction random under the external stimuli, which opens a new insight into the optical regulations. Furthermore, this work combines the in situ growth strategy and first synthesizes the dynamic‐switchable dual‐direction CPL film. Optics in both directions can be inverted simultaneously by exchanging the growth sequences. Finally, multimodal optics, excellent stability, and green manufacturing make them welcome in the advanced anti‐counterfeit areas, with the features of lossless and long‐time useful. [ABSTRACT FROM AUTHOR]

Stimuli responsive optical materials are attractive for many areas, from healthcare to art design. However, creating intricate color‐changing patterns for visual information is still a challenge. This work describes the preparation of mechanochromic structural colored intricate pictures imprinted in cholesteric liquid crystal elastomers by using a chiral isosorbide molecular photoswitch. The photoswitch contains a photoisomerizable cinnamate moiety and was incorporated in a main chain liquid crystal oligomer with photopolymerizable acrylate end groups. After coating, the structural colored film was irradiated with ultraviolet (UV) light in air causing E/Z isomerization of the cinnamate units leading to a redshift of the structural color of the film. A grayscale photomask was used to spatially control the photoisomerization reaction and imprint colorful pictures such as portraits and landscapes, in the cholesteric liquid crystal films with high resolution. Photopolymerization in a nitrogen atmosphere led to a mechanochromic cholesteric liquid crystal elastomer with striking structural colors that blueshift upon strain. The sharp details of the patterns were preserved even under deformation and the system returned to the initial state upon strain removal. Our work offers a simple photoswitch approach to prepare stimuli responsive optical polymers imprinted with color‐changing pictures of unprecedented complexity. [ABSTRACT FROM AUTHOR]

Colloidal photonic crystals reflect light of a certain wavelength, according to the distance between the particles. While the reflective properties are good, the transparency is often hampered by multiple incoherent scattering events. This loss of transparency is primarily due to the large size and high scattering cross section of the particles in close-packed opals, especially in the shorter visible wavelength regime. In this work, a one-step vertical deposition method was used to assemble ZnS@SiO2 core–shell particles within a silica precursor solution to create reflective films with index-matched shells, leading to high transparency. We changed the core particle size and the number of layers to optimize the reflectance and transparency of the films. For small 65 nm core particles, high reflection intensities were difficult to obtain. However, for the 174 nm core particles, incoherent scattering led to decreased transparency. Intermediate sizes were preferred. An optimal film thickness between 2 and 5 μm was determined. If the film thickness was below 2 μm, broad reflection peaks were observed, while thicker films led to a loss of transparency. According to this optimization, red, green, and blue films were created. Last, a stacked RGB film comprising blue, green, and red reflective layers was successfully created by three successive coassembly steps. This was possible due to the high transparency and narrow reflection peak width of each individual coating. These films may have potential as reflective displays and smart windows and in encryption. [ABSTRACT FROM AUTHOR]

Structural color coatings with brilliant color is important in practical applications, such as aesthetic decoration, bionic skins, colorimetric sensors, and other color‐related fields. However, the intrinsic conflict between fast self‐assembly and bright structural color hinders their widespread applications. Here, cholesteric liquid crystal elastomer (CLCE) coatings with brilliant color and mechanochromic response are developed by spraying the cholesteric liquid crystal (CLC) paints followed by evaporation‐induced self‐assembly (EISA) and photocuring. The Marangoni flow within the paints, which drives the orientation of liquid crystal molecules along the flow track in the EISA process, is found to be crucial for achieving both rapid self‐assembly time (60 s) and high reflectivity structural color (42%). The as‐prepared CLCE coatings present uniform structural colors, circularly polarized reflection, and mechanochromic response. Several proof­of­concept applications are also demonstrated, including patterned CLCE coatings on flat substrates, fully covered CLCE coatings on 3D objects, and non‐spectral colors via additive mixing method. The research disclosed herein provides unprecedented levels of efficiency and reliability for preparing structural color coatings. [ABSTRACT FROM AUTHOR]

Mechanochromic materials provide optical changes in response to mechanical stress and are of interest in a wide range of potential applications such as strain sensing, structural health monitoring, and encryption. Advanced manufacturing such as 3D printing enables the fabrication of complex patterns and geometries. In this work, classes of stretchable mechanochromic materials that provide visual color changes when tension is applied, namely, dyes, polymer dispersed liquid crystals, liquid crystal elastomers, cellulose nanocrystals, photonic nanostructures, hydrogels, and hybrid systems (combinations of other classes) are reviewed. For each class, synthesis and processing, as well as the mechanism of color change are discussed. To enable materials selection across the classes, the mechanochromic sensitivity of the different classes of materials are compared. Photonic systems demonstrate high mechanochromic sensitivity (Δnm/% strain), large dynamic color range, and rapid reversibility. Further, the mechanochromic behavior can be predicted using a simple mechanical model. Photonic systems with a wide range of mechanical properties (elastic modulus) have been achieved. The addition of dyes to photonic systems has broadened the dynamic range, i.e., the strain over which there is an optical change. For applications in which irreversible color change is desired, dye-based systems or liquid crystal elastomer systems can be formulated. While many promising applications have been demonstrated, manufacturing uniform color on a large scale remains a challenge. Standardized characterization methods are needed to translate materials to practical applications. The sustainability of mechanochromic materials is also an important consideration. [ABSTRACT FROM AUTHOR]

In this study, a glaze slurry was prepared with different contents of tricalcium phosphate. It was then applied to a fly ash microcrystalline ceramic billet and sintered at 1180 °C for 30 min to prepare the complex. The aim was to obtain a high value-added application of fly ash in order to reduce environmental pollution. The study systematically investigated the influence of the Ca3(PO4)2 content on the crystal phase evolution, physical-mechanical properties, and micro-morphology of the complex. The results showed that products sintered at 1180 °C with 8 wt% Ca3(PO4)2 demonstrated better performance, with a water absorption of 0.03% and a Vickers microhardness of 6.5 GPa. Additionally, the study observed a strong correlation between the Ca3(PO4)2 content and the opacity effect. A feasible opacity mechanism was also proposed to explain the variation of glaze colors and patterns with different contents of Ca3(PO4)2. [ABSTRACT FROM AUTHOR]

A magnetically responsive photonic crystal of colloidal nanosheets can exhibit a controllable structural color, offering diverse potential applications. In this study, we systematically investigated how the lateral sizes of graphene oxide (GO) nanosheets affect their magnetic responsiveness in a photonic system. Contrary to the prediction that larger lateral sizes of nanosheets would be more responsive to an applied magnetic field based on the magnetic energy of anisotropic materials, we discovered that GO nanosheets with larger lateral sizes in the photonic system scarcely responded to a 12 T magnetic field. The lack of magnetic response may be due to the strongly restricted rotational motion of GO nanosheets by mutual electrostatic forces. In contrast, GO nanosheets with medium lateral sizes readily responded to the 12 T magnetic field, forming a uniaxially oriented structure that resulted in a vivid structural color. However, smaller GO nanosheets displayed a less vivid structural color, possibly because of less structural ordering of GO nanosheets. Finally, we found that the photonic crystal of GO nanosheets with optimized lateral sizes responded effectively to the 12 T magnetic field across various GO concentrations, resulting in a vivid and tunable structural color. [ABSTRACT FROM AUTHOR]

Various fascinating optical characteristics in organisms encourage scientists to develop biomimetic synthesis strategies and mimic their unique microstructure. Inspired by the Chameleon's skin with tunable color and superior flexibility, this work designs the evaporated‐induced self‐assembly technique to synthesize the chiral photonic crystal film. Ultrasonic‐intensified and additive‐assisted techniques synergistically optimize the film properties, on the aspects of optic and mechanic. The film shows considerable rigidity and superior flexibility, which can undergo multiple mechanical deformations. Without destroying the chiral nematic structure, the ultimate strain approaches 50%, which exceeds most cellulose‐derived film materials. It also integrates excellent optical performance. The film color can cover the total visible region by tuning the photonic bandgap and has angle‐dependent properties. It can make the response to humidity and solvents, and chromaticity variation reflects the degree of stimulation. Importantly, this structural‐dependent color change is reversible. Lastly, the photonic crystal materials with excellent mechanics and unique optics have been applied in the security. The anti‐counterfeiting material design contains photonic crystal ink, repeatable writing paper, information‐hiding film, and color‐changing labels, with the features of environmentally friendly, economical, non‐destructive, and convenient for authentication. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) are in great demand in many fields because of their unique properties such as high conductivity, chemical stability, lightweight, and high strength. They also received much attention in optical‐related fields because of the super‐black characteristics under visible light and the photothermal effect of infrared light. Recently, the coloration of CNTs under visible light is realized by a simple liquid phase method with the help of silica photonic crystal (PC) coatings. However, the response modulation such as the photoluminescence (PL) property of CNTs to the infrared and ultraviolet (UV) bands is not yet studied. Herein, silane functionalized carbon dots (SiCDs) are introduced into silica PCs, and successfully realized the structural coloration and PL of CNT fibers (CNTFs). The optical and fluorescence visualization of single CNTs and suspended CNT networks (SCNTNs) is also realized with the assistance of SiCDs droplets. These SiCDs‐decorated SiPCs‐coated CNTFs (SiCDs@SiPCs‐CNTFs) exhibit an up/down‐conversion PL response, and the excitation light source can be UV light, visible light, and near‐infrared laser. The structural coloration and the development of new PL properties will promote the wide applications of PL carbon hybrid materials in many fields such as smart displays, intelligent textiles, anti‐counterfeiting, etc. [ABSTRACT FROM AUTHOR]

Structural color is a remarkable physical phenomenon that exists widely in nature. Unlike traditional color rendering methods, they are realized mainly through micro/nanostructures that interfere, diffract, scatter light, and exhibit long‐life and environmental‐friendly color effects. In nature, a few organisms use their color‐changing system to transmit information, such as courtship, warning, or disguise. Meanwhile, some natural inorganic minerals can also exhibit structural colors. Learning from nature, scientists have achieved large‐scale structural color design and manufacturing technology for artificial photonic crystals. Photonic crystals have a unique microstructure that forms a band gap under the action of the periodic potential field, consequently causing Bragg scattering due to the periodic arrangement of different refractive index media within them. Because of the apparent photonic band gap and the ability to form local photons at crystal defects, photonic crystals have been extensively studied in recent years and have broad application prospects in photonic fibers, optical computers, chips, and other fields. In this review, the research, properties, and applications of photonic crystals in recent years are presented, as well as insight into the future developments of photonic crystals. [ABSTRACT FROM AUTHOR]

The PNIPAM/PAphe interpenetrating nanogels which were responsive to temperature and pH were synthesized. The chemical structure, morphology, particle size and dispersity, temperature-and pH-response, structural color tunability, photonic crystal self-assembly, and sol-gel transition behavior of the interpenetrating nanogels were studied in detail by infrared spectroscopy, scanning electron microscopy (SEM), dynamic light scattering, and optical fiber spectrometry. According to the infrared spectrum and SEM image, the effective interpenetration and good monodispersity of the two networks were confirmed. The analysis of particle size and polydispersity index (PDI) indicated that, with the increase of PAphe content, the particle size of the interpenetrating nanogels correspondingly increased, but the monodispersity remained good. The temperature-and pH-sensitivity experiments proved the responsiveness of the interpenetrating nanogels, which showed that the particle size was significantly decreased when the temperature was increased or the pH value was decreased. Combined with the optical fiber spectrum, it was further found that the interpenetrating nanogel could achieve controllable structural colors by adjusting the particle size. More importantly, they possessed the ability of transition from sol to gel above Tp (32 °C) by the method of test tube inversion. These characteristics showed their potential applications in highly controllable optical materials and the biomedical field. [ABSTRACT FROM AUTHOR]

Objectives Methods Results Conclusion Clinical Significance To evaluate the color‐match with extracted natural teeth of three single‐shade universal composites, a group‐shade universal composite, and a highly translucent‐shade conventional composite.Twenty extracted human teeth were divided into light‐ and dark‐shade groups (n = 10, LSG and DSG). A preparation was restored with the 3 single‐shade universal composites, OMNICHROMA (OMC), Admira Fusion x‐tra U (AFU), and Essentia U (ESU); a highly translucent‐shade conventional composite, Tetric EvoCeram T (TEC‐T); and two shades of a group‐shade universal composite—Filtek Universal Restorative (FUR A1 and A4). Composites were photopolymerized, polished, and stored in water for 24 h. The ΔE00 value between the unprepared and restored surfaces was obtained using a spectrophotometer. Composite placement and measurements were repeated three times per tooth. Color differences were statistically analyzed with the within‐between‐subjects t‐test and repeated‐measures analysis of variance (ANOVA), followed by post hoc pairwise comparisons with a Bonferroni adjustment (α = 0.05).There were no statistically significant differences between OMC and FUR (A1 and A4). AFU and ESU showed significantly higher ΔE00 values than OMC and TEC‐T (p < 0.05). Single‐shade composites exhibited significantly higher ΔE00 values in the DSG than in the LSG except ESU (p < 0.05). None of the composites satisfied the criteria for an acceptable match (ΔE00 >1.8).OMC showed the same color matching ability as a group‐shade universal composite. A highly translucent‐shade conventional composite and OMC exhibited better color matching ability than other single‐shade composites. Overall, single‐shade universal composites performed better in lighter‐shaded teeth.Single‐shade universal composites have the potential to reduce chair time by eliminating shade selection in cavities with lighter‐shade teeth. Highly translucent incisal conventional composites also may be used if the appropriate shade of composite is not available. [ABSTRACT FROM AUTHOR]

Creating photonic crystals that can integrate and switch between multiple structural color images will greatly advance their utility in dynamic information transformation, high‐capacity storage, and advanced encryption, but has proven to be highly challenging. Here, it is reported that by programmably integrating newly developed 1D quasi‐periodic folding structures into a 3D photonic crystal, the generated photonic superstructure exhibits distinctive optical effects that combine independently manipulatable specular and anisotropic diffuse reflections within a versatile protein‐based platform, thus creating different optical channels for structural color imaging. The polymorphic transition of the protein format allows for the facile modulation of both folding patterns and photonic lattices and, therefore, the superstructure's spectral response within each channel. The capacity to manipulate the structural assembly of the superstructure enables the programmable encoding of multiple independent patterns into a single system, which can be decoded by the simple adjustment of lighting directions. The multifunctional utility of the photonic platform is demonstrated in information processing, showcasing its ability to achieve multimode transformation of information codes, multi‐code high‐capacity storage, and high‐level numerical information encryption. The present strategy opens new pathways for achieving multichannel transformable imaging, thereby facilitating the development of emerging information conversion, storage, and encryption media using photonic crystals. [ABSTRACT FROM AUTHOR]

[Display omitted] Volatile organic compounds (VOCs) have always been a major concern as a global environmental problem. As a low-cost, high-efficiency and visual sensor, photonic crystals (PCs) have been actively studied in VOCs detection. Herein, a one-dimensional PC sensor for visual sensing of highly toxic benzene series VOC vapors is prepared for the first time by integrating a new photo-crosslinked polymer-poly(styrene-benzoylphenyl acrylate) P(St-BPA) and a high specific surface area metal–organic framework (MOF) MIL-101(Cr). The PC can detect VOCs quantitatively and visually, and clearly distinguish 7 benzene series vapors. The detection limit of the benzene series VOCs is as low as 0.06–3.45 g/m3. Meanwhile, owing to the ultra-thin layer and porous structure, the PC can reach a response equilibrium to the VOCs within 1–2.6 s. Moreover, the PC has a good organic vapor tolerance and can maintain stable optical performance after 1000 times of reuse in VOCs. Besides, 4 other PCs assembled with different aryl polymers and MOFs are first fabricated and their sensing performance to benzene series VOCs are studied and compared, which provides a valuable reference for the selection of materials for the preparation of such PC sensors. [ABSTRACT FROM AUTHOR]

This work proposes a colored intelligent thermal control emitter characterized by adjustable structural color development with a reflection spectrum in the visible light range and intelligent thermal control with temperature switching in the mid infrared wavelength band. In the beginning, we investigate an intelligent thermal control emitter based on a multilayer membrane formed by the phase change material vanadium dioxide, metal material Ag, and dielectric materials Ge and ZnS. By incorporating the thermochromic material vanadium dioxide, the structure exhibits a high emissivity of ε H = 0.85 in the range of 3–13 μm wavelength when in the high temperature metallic state, enabling efficient heat radiation. In the low temperature dielectric state, the structure only has a low emission capacity of ε L = 0.07, reducing energy loss. Our results demonstrate that the structure achieves excellent emission regulation ability (Δ ε = 0.78) through the thermal radiation modulation from high to low temperature, maintaining effective thermal control. Furthermore, the thermal control emitter exhibits selective emission of peak wavelength due to destructive interference and shows a certain independence on polarization and incidence angle. Additionally, the integration of structural color adjustment capability enhances the visual aesthetics of the human experience. The proposed colored intelligent thermal control structure has significant potential for development in aesthetic items such as colored architecture and energy-efficient materials. We propose a colored intelligent thermal control emitter characterized by adjustable structural color development with a reflection spectrum in the visible light range and intelligent thermal control with temperature switching in the mid infrared wavelength band. By incorporating the thermochromic material vanadium dioxide, our results demonstrate that the structure achieves excellent emission regulation ability (Δ ε = 0.78) through the thermal radiation modulation from high to low temperature, maintaining effective thermal control. Additionally, the integration of structural color adjustment capability enhances the visual aesthetics of the human experience. The proposed colored intelligent thermal control structure has significant potential for development in aesthetic items such as colored architecture and energy-efficient materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Cellulose nanocrystals (CNCs) are environmentally friendly building blocks used in the preparation of chiral nematic iridescent films through evaporation‐induced self‐assembly. However, the brittleness of CNC films limits their versatility, especially in applications that require mechanical flexibility. In this study, it is innovatively engineered flexible colored CNC films entirely composed of cellulose by introducing cross‐linked chemically modified cellulose nanofibers (CNFs) as a supporting network. By reducing the surface charge content of CNFs and anchoring them in a network, the disruption to the self‐assembly process of CNCs caused by CNFs is minimized. This effectively preserves the structural colors of CNCs films. Furthermore, the CNFs network enhances the tensile strength and elongation of these all‐cellulose composite films, enabling them to be folded with excellent flexibility while still maintaining a high Young's modulus. Vibrant red, green, and blue‐colored all‐cellulose photonic films can also be achieved by simply adjusting the sonication energy input on the suspension of CNCs. The all‐cellulose‐based flexible films have the potential to be applied as an eco‐friendly and sustainable photonic material when flexibility is essential, for instance, in applications like flexible sensors, anti‐counterfeit labels, or foldable display components. [ABSTRACT FROM AUTHOR]

Structurally colored materials with a color mixing effect are developed using SiO2–ZrN core–shell particles, where ZrN nanoparticles used as shells exhibited localized surface plasmon resonances (LSPRs). ZrN nanoparticles (10–30 nm) are attached to monodispersed SiO2 particles by modifying SiO2 particles with polymers. The attached ZrN nanoparticles exhibited a plasmon resonance absorption band at 700 nm. These SiO2–ZrN core–shell particles have a highly monodisperse particle size and assemble into a particle‐stacked film with Bragg diffraction light in the visible spectrum. The particle‐stacked film of the SiO2–ZrN core–shell particles exhibited the maximum reflection depending on the particle size of the SiO2 core. The ratio of the reflection intensity in the long‐wavelength region corresponding to the ZrN absorption to that in the short‐wavelength region of the particle‐stacked film containing the ZrN shell is less than that of the ratio in only SiO2 particle‐stacked film. The results reveal that these particle‐stacked films exhibit a "color mixing effect" that combines specific wavelength absorption through plasmon resonance and specific wavelength diffraction owing to the periodic structure without using precious metals. [ABSTRACT FROM AUTHOR]

Highlights: Derived from silica photonic crystals, inverse opal microspheres have a regularly connected porous structure and inherit structural color properties. Combined with the stable scaffold and the photothermal phase-transition of the secondary filling material, the inverse opal composite microspheres are endowed with self-healing properties and the ability for controllable drug release. Inverse opal microspheres were significantly treated for diabetic wound, via promoting tissue regeneration, collagen deposition and angiogenesis. Meanwhile, the release of drugs could be monitored by the structural color characteristic. Chronic diabetic wounds confront a significant medical challenge because of increasing prevalence and difficult-healing circumstances. It is vital to develop multifunctional hydrogel dressings, with well-designed morphology and structure to enhance flexibility and effectiveness in wound management. To achieve these, we propose a self-healing hydrogel dressing based on structural color microspheres for wound management. The microsphere comprised a photothermal-responsive inverse opal framework, which was constructed by hyaluronic acid methacryloyl, silk fibroin methacryloyl and black phosphorus quantum dots (BPQDs), and was further re-filled with a dynamic hydrogel. The dynamic hydrogel filler was formed by Knoevenagel condensation reaction between cyanoacetate and benzaldehyde-functionalized dextran (DEX-CA and DEX-BA). Notably, the composite microspheres can be applied arbitrarily, and they can adhere together upon near-infrared irradiation by leveraging the BPQDs-mediated photothermal effect and the thermoreversible stiffness change of dynamic hydrogel. Additionally, eumenitin and vascular endothelial growth factor were co-loaded in the microspheres and their release behavior can be regulated by the same mechanism. Moreover, effective monitoring of the drug release process can be achieved through visual color variations. The microsphere system has demonstrated desired capabilities of controllable drug release and efficient wound management. These characteristics suggest broad prospects for the proposed composite microspheres in clinical applications. [ABSTRACT FROM AUTHOR]

Structural-colored fabrics have been attracting much attention due to their eco-friendliness, dyelessness, and anti-fading properties. Monodisperse microspheres of metal, metal oxide, and semiconductors are promising materials for creating photonic crystals and structural colors owing to their high refractive indices. Herein, Cu2O microspheres were prepared by a two-step reduction method at room temperature; the size of Cu2O microspheres was controlled by changing the molar ratio of citrate to Cu2+; and the size of Cu2O microspheres was tuned from 275 nm to 190 nm. The Cu2O microsphere dispersions were prepared with the monodispersity of Cu2O microspheres. Furthermore, the effect of the concentration of Cu2O microsphere and poly(butyl acrylate) on the structural color was also evaluated. Finally, the stability of the structural color against friction and bending was also tested. The results demonstrated that the different structural colors of fabrics were achieved by adjusting the size of the Cu2O microsphere, and the color fastness of the structural color was improved by using poly(butyl acrylate) as the adhesive. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to modify the FDM 3D printer to print with polystyrene (PS) microspheres as the printing material, thus enabling bottom-up structural color printing and evaluating structural color printing. Design/methodology/approach: This study chose a range of different heated bed temperatures to determine a suitable temperature for accelerating the self-assembly of photonic crystals and printing structural colors on various substrates. In addition, this study enhanced the structural color by doping PS microspheres with different contents of Acid Black 210 dye and evaluated the color-enhanced structural color by eye and spectrophotometer under different light sources. Findings: The results show that the modified 3D printer can be used for structural color printing, and 50°C is determined as the heated bed temperature. There are significant differences in structural colors when printing under different color backgrounds and material substrates, and corresponding suitable substrates should be selected according to the application. The doping of PS microspheres with varying contents of dye results in different color levels of structural color. As with pigment colors, the visual perception of structural color varies when viewed under different light sources. Originality/value: This paper proposes to print structural colors low-costly, analyze structural colors under substrate and light source conditions, and expand the structural color gamut by enhancing structural colors, which has positive implications for further research on structural colors as printing colors. [ABSTRACT FROM AUTHOR]

Opal, a renowned gemstone, exhibits an optical phenomenon known as "play of color," which is classified as a kind of structural color. This unique property makes opal a highly valuable material from the natural science, industry, and humanity perspectives. Opal has a complex internal structure called colloidal polycrystalline, and thus, representations of opal remain unestablished in computer graphics. In this study, to approximate the complex internal structure of opal, we imitate its formation process using the three-dimensional additively weighted Voronoi tessellation and percolation model. Further, we apply path tracing to compute the diffraction patterns of visible light inside opal by utilizing the Ewald construction employed in X-ray diffraction theory. Finally, we achieve a visually plausible output through spectral rendering. [ABSTRACT FROM AUTHOR]

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Hydrogels hold great promise in the field of flexible electronics. Attempts in this area tend to the microstructure design of hydrogels, giving them specific adhesion and multi‐sensing functions. Here, a novel phase separation‐derived anisotropic adhesive structural color hydrogel film is presented for visually flexible electronics. The hydrogel film is generated by template replicating colloidal crystal by using phase separation emulsions of hydrophilic monomer (acrylic acid, AA), hydrophobic monomer (lauryl methacrylate, LMA), co‐monomer ([2‐(methacryloyloxy) ethyl] dimethyl‐(3‐sulfopropyl) ammonium hydroxide (SBMA)), surfactants (hexadecyl trimethyl ammonium bromide, CTAB) and initiator (ammonium persulphate (APS)). The appearance of phase separation results in asymmetric morphologies of hydrogel film, imparting them with anisotropic adhesive performance. Attributed to the formation of inverse opal scaffold structure, the hydrogel film is featured with vivid structural color, showing superior capability in self‐reporting mechanical behavior. Additionally, benefitting from the presence of abundant ions, the hydrogel film exhibits great conductivity. Thus, the resultant hydrogel film is demonstrated with stable dual‐signal sensing properties involving color‐changing and conductivity feedback ability to respond to human activities. These features make the proposed anisotropic adhesive structural color hydrogel film highly potential in the flexible electronic field. [ABSTRACT FROM AUTHOR]

Manipulation of periodic micro/nanostructures in polymer film is of great importance for academics and industrial applications in anticounterfeiting. However, with the increasing demand on information security, materials with time‐dependent features are urgently required, especially the material where the same information can appear more than once on the time scale. Here, one concise strategy to realize time‐dependent anticounterfeiting and "double‐lock" information encryption based on a host‐guest system is proposed, with one photoresponsive azopolymer as the host and one liquid‐crystalline molecule as the guest. The system exhibits a tunable mass transport in pre‐designed periodic micro/nanostructures by tailoring the process of cis‐to‐trans recovery of azo groups and assembly of mesogenic trans‐isomers, resulting in a dynamic structural color in film. Taking advantage of this extraordinary feature, time‐dependent dynamic anticounterfeiting has been achieved. More importantly, the time of each state's appearance in the whole process can be modulated by changing the host‐guest ratio. Combining the manipulatable process of mass transport with the unique decoding method, the stored information in film can be decrypted correctly. This work provides an unprecedented dynamic approach for advanced anticounterfeiting technology with a higher level of security and high‐end applications in information encryption. [ABSTRACT FROM AUTHOR]

Materials with structural coloration capable of multimode color manipulation are gaining growing significance for advanced encryption and high‐security anti‐counterfeiting applications. Among the most promising candidates are naturally derived biomaterials, owing to their renewable, biocompatible, and biodegradable features for developing sustainable, bio‐interfaced photonic platforms. Nevertheless, structural color encryption strategies developed from biological materials usually exhibit limited optical operation modes, lowering their encryption capability and security level. Here, an all‐biomass‐based photonic crystal platform is reported that hierarchically integrates chiral nematic and inverse opal structures through a combination of colloidal assembly, silk protein self‐assembly, and chiral self‐assembly of cellulose nanocrystals, enabling multiplex structural color manipulation in 2D and 3D spaces. The platform's Janus‐style integration brings specular and diffuse reflection, direction‐dependent reflection, circular dichroism, and birefringence into a single form, thereby facilitating multimode structural color tuning in a 2D plane by altering the illumination‐viewing modes. The inherent shape plasticity of silk proteins allows the subsequent creation of 3D photonic platforms with diverse configurations, offering additional spatial flexibility for color encoding. It is demonstrated that this all‐biomass‐based photonic framework exhibits versatile, multilevel, and high‐capacity encryption capability in 2D and 3D spaces, representing an innovative solution to bolster security measures against counterfeiting for future technologies. [ABSTRACT FROM AUTHOR]

Dynamically responsive materials with chromotropic properties have received increasing attention in flexible pressure sensing due to their intuitive nature in the information transfer process. Here, inspired by the biological dynamic regulation of structural color in nature, a robust biomimetic mechanochromic photonic ionogel is ingeniously constructed. The photonic ionogel undergoes continuous and regular structural color changes under compression and outputs stable optical signals, possessing excellent linear pressure responsiveness and stability. The photonic ionogel exhibits sensitive changes in structural color and reflection wavelength via adjusting the lattice spacing of the 3D photonic crystal (mechanochromic sensitivity: 2.21 nm per %, Δλ > 150 nm). Furthermore, the good compatibility between ionogel and PC microspheres endows photonic ionogel with good linear pressure responsiveness (R2 ≈ 0.984). Meanwhile, ionic liquid (IL) and the covalent cross-linking network of robust polyurethane elastomer provide photonic ionogel with a wide temperature tolerance range (Tg ≈ −49.5 °C, initial decomposition temperature of 301 °C) and mechanical durability (5000 cycles of compression). This work demonstrates promising applications not only in flexible pressure sensing but also in advanced visual interaction devices. [ABSTRACT FROM AUTHOR]