Search Results (17)

Electrochromic devices (ECDs) capable of modulating both visible color and infrared (IR) emissivity are promising for applications in smart thermal camouflage and multifunctional displays. However, conventional transmissive ECDs suffer from limited IR modulation due to the low IR transmittance of transparent electrodes. Here, we report a reflection-type electrochromic zinc-ion battery (HWEC-ZIB) using a self-doped polyaniline nanorod film (SP(ANI-MA)) as the active layer. By positioning the active material at the device surface, this structure avoids interference from transparent electrodes and enables broadband and efficient IR emissivity tuning. To prevent electrolyte-induced IR absorption, a thermal lamination encapsulation method is employed. The optimized device achieves emissivity modulation ranges of 0.28 (3–5 μm) and 0.19 (8–14 μm), delivering excellent thermal camouflage performance. It also exhibits a visible color change from earthy yellow to deep green, suitable for various natural environments. In addition, the HWEC-ZIB shows a high areal capacity of 72.15 mAh cm⁻² at 0.1 mA cm⁻² and maintains 80% capacity after 5000 cycles, demonstrating outstanding electrochemical stability. This work offers a versatile device platform integrating IR stealth, visual camouflage, and energy storage, providing a promising solution for next-generation adaptive camouflage and defense-oriented electronics. Full article

Electrochromic fabrics (ECFs) can be applied to wearable displays and military camouflage clothing, and they have great potential in developing wearable products. Current ECFs are often bulky, involve complicated processes, and have high production costs. In this study, we report a novel strategy for preparing electrochromic fabrics that require only a three-layer structure: cotton fabric as the substrate, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the electrochromic layer and the electrodes, and an ion-conducting film (ICF) bonded to the fabric by hot pressing. Compared with conventional ECFs, this method does not require the extra preparation of electrode layers on the fabric, as these layers affect the color-changing effect. Hot pressing eliminates the need for a complex sealing process and is more suitable for fabrics with poor wicking effects, which increases the method’s applicability. Cotton fabrics offer the value of biodegradability and are more environmentally friendly. Meanwhile, unlike carbon cloth, the fabric’s color does not interfere with the electrochromic effect. The ICF is non-liquid and can maintain the dryness of the fabric. Additionally, the ICF provides high-temperature protection up to 150 °C. The ECFs exhibit exceptional thinness at 161 µm and a lightweight construction with a 0.03 g/cm² weight. Furthermore, the ECFs exhibit a relatively long sustain time of 115 min without voltage, demonstrating impressive performance. Improved peel strength to 7.11 N is achieved through an improved hot-pressing process. The development strategy for ECFs can also be applied to other electrochromic substances, potentially advancing intelligent applications such as wearable fabrics and military camouflage while promoting rapid progress in electrochromic fabrics. Full article

This study focused on developing pigmented linear low-density polyethylene (LLDPE) sheets while preserving their mechanical properties and infrared (IR) transparency. Six pigments—ZnO, ZnS, TiO₂, FeO yellow, FeO light brown, and FeO dark brown—were each mixed with polyethylene (PE) wax in a 1:1 ratio and blended with LLDPE at concentrations of 1, 3, and 5 wt%. Tensile strength tests showed minimal changes at lower pigment concentrations, with values near that of pure LLDPE (14 MPa), and slight reductions at 5 wt%. IR transparency tests, conducted using both direct and reflected heat sources, showed that white-pigmented sheets maintained over 85% transparency, while colored pigments exhibited slightly reduced IR transmittance, ranging from 70% to 91%. Fourier Transform Infrared Spectroscopy (FTIR) analysis confirmed that the critical IR transparency range of 8–12 μm remained unaffected with both pure and pigmented sheets. On the other hand, ultraviolet–visible (UV–VIS) testing showed that white-pigmented sheets experienced enhanced visible-light absorption with increasing pigment concentration and thickness, while color-pigmented sheets exhibited high opacity. Additionally, micro-structuring was performed on the LLDPE sheets to further modify their IR properties, which resulted in effective scattering of IR radiation. These findings highlight the potential of pigmented LLDPE sheets for applications requiring both visual opacity and IR transparency, such as thermal management and camouflage, as well as applications requiring tunable IR properties. Full article

Camouflaged object detection (COD) is a challenging task, aimed at segmenting objects that are similar in color and texture to their background. Sufficient multi-scale feature fusion is crucial for accurately segmenting object regions. However, most methods usually focus on information compensation, overlooking the difference between features, which is important for distinguishing the object from the background. To this end, we propose the cross-level iterative subtraction network (CISNet), which integrates information from cross-layer features and enhances details through iteration mechanisms. CISNet involves a cross-level iterative structure (CIS) for feature complementarity, where texture information is used to enrich high-level features and semantic information is used to enhance low-level features. In particular, we present a multi-scale strip convolution subtraction (MSCSub) module within CIS to extract difference information between cross-level features and fuse multi-scale features, which improves the feature representation and guides accurate segmentation. Furthermore, an enhanced guided attention (EGA) module is presented to refine features by deeply mining local context information and capturing a broader range of relationships between different feature maps in a top-down manner. Extensive experiments conducted on four benchmark datasets demonstrate that our model outperforms the state-of-the-art COD models in all evaluation metrics. Full article

Constructing photonic crystals with core-shell structured nanoparticles is an important means for applications such as secure communication, anti-counterfeiting marking, and structural color camouflage. Nonetheless, the precise synthesis technology for core-shell structured nanoparticles at the hundred-nanometer scale faces significant challenges. This paper proposes a controlled synthesis method for core-shell structured nanoparticles using a template method. By using 100 nm diameter silica nanospheres as templates and coating them with a ferroferric oxide shell layer, SiO₂@Fe₃O₄ core-shell structured nanoparticles with regular morphology and good uniformity can be obtained. The study experimentally investigated the effects of feed amount, modifiers, temperature, and feed order on the coating effect, systematically optimizing the preparation process. Centrifugal driving technology was used to achieve structural colors in the visible wavelength range. Additionally, the method successfully created well-defined and uniform core-shell structured nanoparticles using 200 nm diameter silica nanospheres as templates, demonstrating that this controllable synthesis method can effectively produce core-shell structured nanoparticles over a wide range of particle sizes. The template method proposed in this paper can significantly improve morphological regularity and size uniformity while effectively reducing the preparation cost of core-shell structured nanoparticles. Full article

Creatures in nature make extensive use of structural color adaptive camouflage to survive. Cholesteric liquid crystals, with nanostructures similar to those of natural organisms, can be combined with actuators to produce bright structural colors in response to a wide range of stimuli. Structural colors modulated by nano-helical structures can continuously and selectively reflect specific wavelengths of light, breaking the limit of colors recognizable by the human eye. In this review, the current state of research on cholesteric liquid crystal photonic actuators and their technological applications is presented. First, the basic concepts of cholesteric liquid crystals and their nanostructural modulation are outlined. Then, the cholesteric liquid crystal photonic actuators responding to different stimuli (mechanical, thermal, electrical, light, humidity, magnetic, pneumatic) are presented. This review describes the practical applications of cholesteric liquid crystal photonic actuators and summarizes the prospects for the development of these advanced structures as well as the challenges and their promising applications. Full article

Bioinspired structural color represents a burgeoning field that draws upon principles, strategies, and concepts derived from biological systems to inspire the design of novel technologies or products featuring reversible color changing mechanisms, with significant potential applications for camouflage, sensors, anticounterfeiting, etc. This mini-review focuses specifically on the research progress of bioinspired structural color in the realm of camouflage. Firstly, it discusses fundamental mechanisms of coloration in biological systems, encompassing pigmentation, structural coloration, fluorescence, and bioluminescence. Subsequently, it delineates three modulation strategies—namely, photonic crystals, film interference, and plasmonic modulation—that contribute to the development of bioinspired structural color materials or devices. Moreover, the review critically assesses the integration of bioinspired structural color materials with environmental contexts, with a particular emphasis on their application in camouflage. Finally, the paper outlines persisting challenges and suggests future development trends in the camouflage field via bioinspired structural color. Full article

Polarization imaging has achieved a wide range of applications in military and civilian fields such as camouflage detection and autonomous driving. However, when the imaging environment involves a low-light condition, the number of photons is low and the photon transmittance of the conventional Division-of-Focal-Plane (DoFP) structure is small. Therefore, the traditional demosaicing methods are often used to deal with the serious noise and distortion generated by polarization demosaicing in low-light environment. Based on the aforementioned issues, this paper proposes a model called Low-Light Sparse Polarization Demosaicing Network (LLSPD-Net) for simulating a sparse polarization sensor acquisition of polarization images in low-light environments. The model consists of two parts: an intensity image enhancement network and a Stokes vector complementation network. In this work, the intensity image enhancement network is used to enhance low-light images and obtain high-quality RGB images, while the Stokes vector is used to complement the network. We discard the traditional idea of polarization intensity image interpolation and instead design a polarization demosaicing method with Stokes vector complementation. By using the enhanced intensity image as a guide, the completion of the Stokes vector is achieved. In addition, to train our network, we collected a dataset of paired color polarization images that includes both low-light and regular-light conditions. A comparison with state-of-the-art methods on both self-constructed and publicly available datasets reveals that our model outperforms traditional low-light image enhancement demosaicing methods in both qualitative and quantitative experiments. Full article

The aim of this work was to design a kirigami-based metamaterial with optical properties. This idea came from the necessity of a study that can improve common camouflage techniques to yield a product that is cheap, light, and easy to manufacture and assemble. The author investigated the possibility of exploiting a rotation to achieve transparency and color changing. One of the most important examples of a kirigami structure is a geometry based on rotating squares, which is a one-degree-of-freedom mechanism. In this study, light polarization and birefringence were exploited to obtain transparency and color-changing properties using two polarizers and common cellophane tape. These elements were assembled with a rotating-square structure that allowed the rotation of a polarizer placed on the structure with respect to a fixed polarizer equipped with cellophane layers. Full article

In nature, some organisms have the ability to camouflage to adapt to environmental changes; they blend with the environment by changing their skin colors. Such a phenomenon is of great significance for the research of adaptive camouflage materials. In this study, we propose a novel design scheme for the study of angle-independent photonic materials and successfully prepare an electrically tunable multi-color display angle-independent inverse opal photonic gel (IOPG). After photopolymerization of hydroxyethyl methacrylate with ionizable monomer acrylic acid (AA) in a long-range disordered opal template and etching, the angle-independent inverse opal photonic gel is obtained, presenting a single structural color. The electrically responsive color changes can be achieved at different angles. The color of the disordered AA-IOPG changes from green to blue-green when applying +4 V bias voltage and from green to orange when applying −4 V bias voltage. The electrochromism of the disordered AA-IOPG is mainly due to the local pH change caused by water electrolysis under bias voltage, which leads to a change of the swelling ratio. The disordered AA-IOPG shows high color tunability and durability through repeated opposite bias voltage tests, indicating that it is a promising conductive photonic material. Full article

Structural coloration has become a fascinating field of research, inspiring scientists and engineers to explore the vibrant colors observed in nature and develop bio-inspired photonic structures for various applications. Cellulose-based materials derived from plant fibers offer a promising platform for mimicking natural photonic structures. Their abundance, renewability, and versatility in form and structure make them ideal for engineering specific optical properties. Self-assembly techniques enable the creation of ordered, periodic structures at the nanoscale by manipulating the interactions between cellulose fibers through chemical modification or physical manipulation. Alternatively, additive manufacturing techniques like 3D printing and nanoimprint lithography can directly fabricate desired structures. By em-ulating natural photonic structures, cellulose-based materials hold immense potential for applications such as colorimetric sensors, optoelectronic devices, camouflage, and decorative materials. However, further research is needed to fully com-prehend and control their optical properties, as well as develop cost-effective and scalable manufacturing processes. This article presents a comprehensive review of the fundaments behind natural structural colors exhibited by living organisms and their bio-inspired artificial counterparts. Emphasis is placed on understanding the underlying mechanisms, strategies for tunability, and potential applications of these photonic nanostructures, with special focus on the utilization of cellulose nanocrystals (CNCs) for fabricating photonic materials with visible structural color. The challenges and future prospects of these materials are also discussed, highlighting the potential for advancements to unlock the full potential of cellulose-based materials with structural color. Full article

Clinobisvanite (monoclinic scheelite BiVO₄, S.G.I2/b) has garnered interest as a wide-band semiconductor with photocatalyst activity, as a high NIR reflectance material for camouflage and cool pigments and as a photoanode for PEC application from seawater. BiVO₄ exists in four polymorphs: orthorhombic, zircon-tetragonal, monoclinic, and scheelite-tetragonal structures. In these crystal structures, V is coordinated by four O atoms in tetrahedral coordination and each Bi is coordinated to eight O atoms from eight different VO₄ tetrahedral units. The synthesis and characterization of doped bismuth vanadate with Ca and Cr are studied using gel methods (coprecipitated and citrate metal–organic gels), which are compared with the ceramic route by means of the UV–vis–NIR spectroscopy of diffuse reflectance studies, band gap measurement, photocatalytic activity on Orange II and its relation with the chemical crystallography analyzed by the XRD, SEM-EDX and TEM-SAD techniques. The preparation of bismuth vanadate-based materials doped with calcium or chromium with various functionalities is addressed (a) as pigments for paints and for glazes in the chrome samples, with a color gradation from turquoise to black, depending on whether the synthesis is by the conventional ceramic route or by means of citrate gels, respectively; (b) with high NIR reflectance values that make them suitable as fresh pigments, to refresh the walls or roofs of buildings colored with them; and (c) with photocatalytic activity. Full article

Accurately segmenting an insect from its original ecological image is the core technology restricting the accuracy and efficiency of automatic recognition. However, the performance of existing segmentation methods is unsatisfactory in insect images shot in wild backgrounds on account of challenges: various sizes, similar colors or textures to the surroundings, transparent body parts and vague outlines. These challenges of image segmentation are accentuated when dealing with camouflaged insects. Here, we developed an insect image segmentation method based on deep learning termed the progressive refinement network (PRNet), especially for camouflaged insects. Unlike existing insect segmentation methods, PRNet captures the possible scale and location of insects by extracting the contextual information of the image, and fuses comprehensive features to suppress distractors, thereby clearly segmenting insect outlines. Experimental results based on 1900 camouflaged insect images demonstrated that PRNet could effectively segment the camouflaged insects and achieved superior detection performance, with a mean absolute error of 3.2%, pixel-matching degree of 89.7%, structural similarity of 83.6%, and precision and recall error of 72%, which achieved improvements of 8.1%, 25.9%, 19.5%, and 35.8%, respectively, when compared to the recent salient object detection methods. As a foundational technology for insect detection, PRNet provides new opportunities for understanding insect camouflage, and also has the potential to lead to a step progress in the accuracy of the intelligent identification of general insects, and even being an ultimate insect detector. Full article

Functional polymers featuring good processability in non-halogenated, benzene-free green solvents are highly desired due to health and environmental concerns. Herein, a series of novel D-A type conjugated polymers, PBDT-IIDs, are designed and successfully prepared by “green” functionalization of the polymers with highly hydrophilic, highly polar, highly flexible, and biocompatible oligoethylene glycol (OEG) side chains in order to improve the processability. These series polymers are named PBDT-IID2, PBDT-IID3, and PBDT-IID4, respectively, according to the number of oxygen atoms in the side chain. After confirmation by structural characterization, the basic properties of PBDT-IIDs are also investigated. With the increase in the OEG side chain length, the polymer PBDT-IID4 not only has good solubility in the halogen solvent chlorobenzene, but also exhibits excellent solubility in the green halogen-free solvent methyltetrahydrofuran (Me-THF). As a result, the green solvent Me-THF can also be applied to prepare PBDT-IIDs’ electrochromic active layers, except for chlorobenzene and toluene. The electrochromism of PBDT IIDs under both positive and negative voltages has a practical application potential. The several controllable switches between dark green and khaki (0–0.6 V) are expected to show great potential in the field of military camouflage. Furthermore, according to the principle of red, green, and blue (RGB) mixing, light blue-green in the reduced state (−1.6 V) can be used in the preparation of complementary ECDs to provide one of the three primary colors (green). Full article

Some cephalopods (squids, octopuses, and cuttlefishes) produce dynamic structural colors, for camouflage or communication. The key to this remarkable capability is one group of specialized cells called iridocytes, which contain aligned membrane-enclosed platelets of high-reflective reflectins and work as intracellular Bragg reflectors. These reflectins have unusual amino acid compositions and sequential properties, which endows them with functional characteristics: an extremely high reflective index among natural proteins and the ability to answer various environmental stimuli. Based on their unique material composition and responsive self-organization properties, the material community has developed an impressive array of reflectin- or iridocyte-inspired optical systems with distinct tunable reflectance according to a series of internal and external factors. More recently, scientists have made creative attempts to engineer mammalian cells to explore the function potentials of reflectin proteins as well as their working mechanism in the cellular environment. Progress in wide scientific areas (biophysics, genomics, gene editing, etc.) brings in new opportunities to better understand reflectins and new approaches to fully utilize them. The work introduced the composition features, biochemical properties, the latest developments, future considerations of reflectins, and their inspiration applications to give newcomers a comprehensive understanding and mutually exchanged knowledge from different communities (e.g., biology and material). Full article