Multispectral camouflage for infrared, visible, lasers and microwave with radiative cooling

Visible light compatible infrared stealth capability based on phase change materials

This study utilizes thermochromic phase change materials VO2 and GST to design micro-nano structures with temperature-tunable thermal emission characteristics, further controlling their stealth effects in both visible light and infrared backgrounds. Initially, an infrared stealth structure based on GST is proposed. By exploring its crystalline (cGST) and amorphous (aGST) states, the optimal thickness of GST is determined to be 250 nm. The structures corresponding to aGST and cGST exhibit emissions of 0.24 and 0.24, respectively, in the atmospheric window of 3-5 μm and 0.03 and 0.15 at 8-14 μm. These low emission capabilities aid in achieving infrared stealth. In the non-atmospheric window of 5-8 μm, the emissions are 0.06 and 0.76, which can help reduce heat loss at low temperatures and radiate energy at high temperatures, thus optimizing the stealth effect. Subsequently, a ZnS layer is added on top to regulate the structural color. By scanning the thickness of ZnS in different states of GST, we investigate the chromaticity coordinates of the structure in amorphous, crystalline, and mixed states with varying crystal proportions. From the perspective of infrared emissivity, the feasibility of visible light stealth is studied. A ZnS layer thickness of 150 nm is selected as the optimal parameter, determining the infrared emissivity for both states. The structures corresponding to aGST and cGST exhibit emissions of 0.17 and 0.22 in the atmospheric window of 3-5 μm and 0.03 and 0.20 at 8-14 μm. The low emission capabilities help achieve infrared stealth, while the emissions within the non-atmospheric window of 5-8 μm are 0.10 and 0.77. The reasons for resonance absorption are explained by calculating the normalized electric field and energy dissipation intensity. Finally, a VO2 layer is added. Due to the reversible nature of the VO2 phase change, two phase change materials at different temperatures result in four states. The thickness of the VO2 layer is varied to explore the infrared emissivity in different states. This study primarily focuses on designing dynamically tunable micro-nano structures by combining phase change materials, achieving precise control over reflection and emission characteristics in both visible light and infrared bands, thus providing more possibilities for stealth technology.

Microwave-Infrared Compatible Camouflage by MXene-Based Composite Aerogels via Synergistic Electromagnetic, Emissivity, and Thermal Regulation

The advancement of multispectral surveillance technologies has rendered conventional single-band camouflage materials ineffective, driving an urgent demand for multispectral-compatible stealth materials. Herein, we report a multidimensional MXene-based composite aerogel engineered via cost-effective lyophilization for radar-infrared compatible camouflage. As building blocks, few-layer Ti3C2Tx MXene nanosheets functionalized with NiB alloy nanoparticles and thermoresponsive VO2 phase-change materials are cross-linked by poly(vinyl alcohol) to construct the MXene/NiB/VO2 composite aerogel through one-step cryo-assembly. The composite demonstrates a remarkable multispectral stealth performance. The thermal radiation temperature of a heated target is reduced from 180 to 55 °C. In addition, a minimum reflection loss (RLmin) of -54.7 dB with an effective absorption bandwidth of 7.1 GHz (8.8-15.9 GHz) at an ultralow low density of 19 mg·cm-3 has been achieved. These breakthroughs stem from synergistic mechanisms: low infrared emissivity, suppressed thermal conduction, dynamic temperature regulation via the VO2 phase transition, and multimodal electromagnetic dissipation. This work establishes a material design paradigm to reconcile infrared-microwave spectral incompatibilities through multidimensional heterostructure engineering, providing a roadmap for next-generation adaptive multispectral stealth technologies.

Multimodal Visible-Infrared Subwavelength Structures with Decoupled Modulation of Reflection Spectra

Visible-infrared reflectivity carries an important part of identity information for most kinds of objects, and its decoupled modulation holds significant application value in the field of identity information reconstruction, such as display, camouflage, and anticounterfeiting. Some well-designed materials or devices have exhibited remarkable abilities in the decoupled modulation of optical reflectivity, but it is difficult to concisely describe their modulation performance as the involved controllable reflectivity characteristics are at least two. Here, a systematic evaluation strategy that comprehensively assesses both the decoupling degree and the changing range through a single quantitative indicator is first proposed, and a set of subwavelength structures is presented for the complex decoupled modulation of four visible-infrared reflectivity characteristics. The decoupled modulation ability of the subwavelength structures is evaluated utilizing the new strategy, where the magnitudes of the indicators align with the modulation flexibility, thus verifying the validity of the proposed evaluation approach. The set of structures possesses robustness and can be fabricated by a controllable electrochemical process. Based on the obtained modulation structures, a multiple identity information display is successfully implemented.

Tri-spectral decoupled programmable thermal emitter for multimode camouflage with heterogeneous phase-change integration

Camouflage technology requires tailoring of the optical characteristics of objects against possible detection. Currently, there are three essential spectra, namely, 0.36-0.83 μm, 3-5 μm, and 8-14 μm, corresponding to the commonly used visible camera and thermal detectors. Thus, to fulfil the mentioned requirement, herein, we present the efficient design and optimization of a tri-spectral decoupled thermal emitter using a heterogeneous integrated phase-change material (PCM) multilayer composed of vanadium dioxide (VO2) and In3SbTe2 (IST). This thermal emitter could theoretically feature both structural colors across the visible range and independently programmable emissivity modulation with up to 80% absolute tuning in two infrared detection regions. Additionally, two methods for achieving confusing and deceptive colored thermal camouflage are proposed based on this thermal emitter, enhancing camouflage disorientation capabilities and enabling the generation of deceptive infrared images that mimic other objects. Thus, this work offers a near-perfect solution with flexible designs for camouflage in complex environments.

Femtosecond laser fabrication metasurface emitter for multispectral camouflage

The powerful electromagnetic capability of a metasurface makes it a good candidate for thermal emission manipulation toward promising infrared (IR) camouflage and thermal management technology. Here, a metasurface-based infrared is fabricated to achieve multispectral camouflage as well as radiative cooling simultaneously. Cross-scale processing on metal-dielectric composite films is successfully achieved by femtosecond laser direct writing (FsLDW), which is proven to be an efficient and feasible technique in metasurface fabrication. The prepared emitter exhibits low emissivity (ɛ3-5 μm = 0.32, ɛ8-14 μm = 0.31) in atmospheric windows but high absorption in 10.6 μm so that it can effectively evade the tracking of infrared detectors and laser radars. Besides, the emitter also has high emissivity in the undetected band (ɛ5-8 μm = 0.66) to dissipate possible heat accumulation. The proposed metasurface design and fabrication method empowers new ideas for the generation of optical devices toward multispectral camouflage and radiative cooling compatibility.

A Colorful Electrochromic Infrared Emissivity Regulator for All-Season Intelligent Thermal Management in Buildings

Radiative cooling is a technology that utilizes the high emissivity of materials in the atmospheric window to achieve cooling, showing great application prospects in building energy-saving. However, traditional static passive radiative cooling materials with broad-spectrum high emissivity can lead to increased heating energy consumption in winter due to overcooling and a weakened cooling effect in summer due to the urban heat island effect. In this study, a colorful, intelligent infrared emissivity regulator is well designed based on a multi film ultrathin electrochromic device for all-season thermal management in buildings. The infrared emissivity of the regulator can vary in real time in response to seasonal or temperature variations, allowing for the switching between radiative cooling and insulation. Guided by nano-photonics theory for multilayer optical films, the regulator achieves multi-modal dynamic infrared emissivity regulation in the atmospheric windowΔ ε ¯ $\Delta \ \bar{\varepsilon }$ Δ ε ¯ $\Delta \ \bar{\varepsilon }$ , and the high reflectance in the non-atmospheric window inhibits heat gains from the external environment. The regulator demonstrates excellent environmental adaptivity with an acceptable response time, a long cycle life, and good bending resistance. The regulator can achieve ≈2 °C/3 °C (nighttime/daytime) temperature adjustment. The simulation results indicate that the regulator can achieve an annual building energy saving of 3.46 MJ m- 2.

Ultrabreathable Open-Cell Hierarchical Pore Structure for Radiative Cooling Protective Membranes

Personal protective clothing is essential in biochemical threat environments, however balancing protection, thermal comfort, and breathability remains a significant challenge. This work introduces a novel, skin-friendly ultrabreathable radiative cooling protective membrane (Ub-RCPM), which is developed via a one-step evaporation-induced pore formation process. The sequential evaporation of solvent and nonsolvent during the process endows an ultrabreathable open-cell hierarchical pore structure. By adjusting the open-cell size, Ub-RCPM simultaneously offers high protection, moisture permeability, and passive radiative cooling. The hierarchical pore structure demonstrates a sunlight reflectivity of 94.79% and an infrared emissivity of 94.53% through the infrared atmospheric window, which enables efficient passive cooling. Its open-cell structure enables a water vapor transmission rate of 8904.59 g m-2 day-1, 3.5 times higher than that of commercial protection clothing. Additionally, the submicron pores provide a filtration efficiency of 99.1% for 75 nm aerosols. The combination of radiative cooling and ultrahigh breathability enables Ub-RCPM to a temperature lower than commercial protective clothing by 9.6-16.5 °C in real-world conditions. This presents a groundbreaking approach for the design of future thermal comfortable personal protective clothing.

Polarization-Independent Broadband Infrared Selective Absorber Based on Multilayer Thin Film

Spectrally selective infrared absorbers play a pivotal role in enabling optoelectronic applications such as infrared detection, thermal imaging, and photothermal conversion. In this paper, a dual-band wide-spectrum infrared selective absorber based on a metal-dielectric multilayer structure is designed. Through optimized design, the absorptance of the absorber reaches the peak values of 0.87 and 1.0 in the target bands (3-5 μm and 8-14 μm), while maintaining a low absorptance of about 0.2 in the non-working bands of 5-8 μm, with excellent spectral selectivity. By analyzing the Poynting vector and loss distribution, the synergistic mechanism of the ultra-thin metal localized enhancement effect, impedance matching, and intrinsic absorption of the material is revealed. This structure exhibits good polarization-insensitive characteristics and angle robustness within a large incident angle range, showing strong adaptability to complex optical field environments. Moreover, the proposed planarized structure design is compatible with standard fabrication processes and has good scalability, which can be applied to other electromagnetic wave bands. This research provides new design ideas and technical solutions for advanced optoelectronic applications such as radiation cooling, infrared stealth, and thermal radiation regulation.

Free-space high-Q nanophotonics

High-Q nanophotonic devices hold great importance in both fundamental research and engineering applications. Their ability to provide high spectral resolution and enhanced light-matter interactions makes them promising in various fields such as sensing, filters, lasing, nonlinear optics, photodetection, coherent thermal emission, and laser stealth. While Q-factors as large as 109 have been achieved experimentally in on-chip microresonators, these modes are excited through near-field coupling of optical fibers. Exciting high-Q modes via free-space light presents a significant challenge primarily due to the larger fabrication area and more lossy channels associated with free-space nanophotonic devices. This Review provides a comprehensive overview of the methods employed to achieve high-Q modes, highlights recent research progress and applications, and discusses the existing challenges as well as the prospects in the field of free-space high-Q nanophotonics.

Co-Doped ErFeO3 for Dual-Band Laser Absorption with High-Temperature Stability

The development of multi-band laser suppression materials has been driven by the limitations of single-band laser suppression materials. Inorganic ceramic materials, compared with organic laser suppression materials, photonic crystals, and metamaterials, offer significant advantages in fabrication methods and environmental stability. In this study, Co3+ ions, with relatively higher electronegativity, were introduced to substitute some Fe ion sites in ErFeO3. This substitution caused distortion in the crystal structure, reduced the unit cell volume, and altered the band structure. As a result, the band gap was reduced compared with that of ErFeO3, and the unique energy level transitions of Er ions were activated. This led to dual-band laser suppression with reflectances of 22.16% at 1064 nm and 35.63% at 1540 nm. Furthermore, after high-temperature testing at 1100 °C in air, the laser absorption performance could still be maintained with the intensity retention above 95%. This unique strategy for improving the band structure provides significant potential for applications in laser suppression.

Inverse Design of Active-Source Metamaterials for Thermal Camouflage with Arbitrary Active Sources

Precise control of active-source thermal fields is critical for advanced technological applications, including thermal camouflage, thermal protection, and energy harvesting. However, the inherent heat generation from active sources often results in localized high-temperature regions and complex, non-linear heat flux distributions, posing significant challenges for effectively managing these thermal fields. Here, a novel theoretical design framework is presented for active-source metamaterials (ASM) by integrating inverse design principles with advanced transformation thermotics. This ASM framework allows for the conversion of complex active-source effects into tailored anisotropic thermal conductivity distributions, thus enabling precise modulation of active-source thermal fields for a variety of advanced applications. As a proof-of-concept, the precise thermal camouflage of active sources is demonstrated, ranging from simple circular geometries to more complex multi-leaf configurations, and systematically investigate the interactions between the temperature fields, heat flux distributions, and the power of active sources. Both numerical simulations and experimental validations are conducted to substantiate the effectiveness of the proposed approach. The work establishes a versatile framework for the precise management of active-source thermal fields, offering significant potential for applications in fields such as chip design, battery technology, and energy systems.

Flexible multilayer film structure for visible-laser-infrared compatible camouflage

With the rapid advancement of detection technologies, the demand for multi-band compatible camouflage solutions has significantly increased. In this study, we propose a flexible meta-coating based on a polyimide (PI) substrate, featuring a double Fabry-Perot cavity for effective camouflage across visible-near-infrared laser-infrared bands. The visible color of the structure can be tuned by adjusting the thickness of the top dielectric layer, enabling selective reflection of specific light wavelengths. In the infrared atmospheric window, the multilayer film exhibits low average emissivity (ε3-5μm = 0.16, ε8-14μm = 0.18), providing efficient thermal camouflage. Conversely, in the non-atmospheric infrared window, the film shows higher emissivity (ε5-8μm = 0.63), facilitating effective radiation heat dissipation. Experimental results show that the surface temperature of the structure is 183.5°C when heated to 210°C, which is 17°C lower than that of an Al wafer under the same conditions. Additionally, the structure demonstrates high low reflectivity at 1.06 μm (ε1.06μm = 0.94) and 1.55 μm (ε1.55μm = 0.99), making it suitable for visible light-laser-infrared. This work provides a feasible solution for large-area, low-cost, heat-resistant, and multispectral-compatible camouflage, with potential applications in military applications.

Cost-Effective Inorganic Multilayer Film for High-Performance Daytime Radiative Cooling

Inorganic multilayer films for radiative cooling have garnered significant attention due to their exceptional resistance to photothermal degradation. However, the design and fabrication of structurally simple and cost-effective inorganic multilayer films remain challenging due to limitations in material properties and the preparation process. This study develops a structurally simple inorganic multilayer film (Si3N4/SiO2/Al2O3/Si3N4/Al) for daytime radiative cooling. Instead of the conventional periodic alternation of high and low refractive indices (H-L…H-L), this work proposes a H-L-L-H symmetric multilayer film structure to achieve improved radiative cooling performance. The fabricated multilayer film demonstrates superior radiative cooling properties and lower thickness than that in the current studies using Al as the reflective layer, achieving a solar reflectance of 89.57%, an atmospheric window (8-13 μm) emissivity of 83.41%, and a net cooling power of 63.38 W·m-2. Under direct sunlight, the multilayer film demonstrated a maximum temperature reduction of approximately 3 °C compared to the reference sample. By employing a thermal treatment process for the Si3N4 layer, the poor adhesion between the Al layer and the Si3N4 layer is successfully addressed without compromising optical performance. The underlying physical mechanisms are also elucidated. This work provides an effective strategy for developing daytime radiative cooling inorganic multilayer films suitable for large-scale industrial production.

Colored Radiative Cooling: from Photonic Approaches to Fluorescent Colors and Beyond

Radiative cooling technology is gaining prominence as a sustainable solution for improving thermal comfort and reducing energy consumption associated with cooling demands. To meet diverse functional requirements such as aesthetics, switchable cooling, camouflage, and colored smart windows, color is often preferred over a white opaque appearance in the design of radiative cooling materials. Colored radiative cooling (CRC) has emerged as a prevailing technology not only for achieving a colorful appearance but also for increasing the effective solar reflectance to enhance cooling performance (through the incorporation of fluorescent materials). This paper reviews recent advancements in CRC and its profound impact on energy savings and real-world applications. After introducing the fundamentals of CRC and color characterization, various photonic approaches are explored that leverage resonant structures to achieve coloration in radiative cooling, comparing them with conventional coloration methods based on optical materials like fluorescent pigments that can convert absorbed ultraviolet light into visible-light emission. Furthermore, the review delves into self-adaptive CRC materials featuring dynamic optical modulation that responds to temperature fluctuations. Lastly, the potential application of CRC materials is assessed, a comprehensive outlook on their future development is offered, and the critical challenges in practical applications are discussed.

Semimetal-dielectric-metal metasurface for infrared camouflage with high-performance energy dissipation in non-atmospheric transparency window

The development of novel camouflage technologies is of great significance, exerting an impact on both fundamental science and diverse military and civilian applications. Effective camouflage aims to reduce the recognizability of an object, making it to effortlessly blend with the environment. For infrared camouflage, it necessitates precise control over surface emissivity and temperature to ensure that the target blends effectively with the surrounding infrared background. This study presents a semimetal-dielectric-metal metasurface emitter engineered for the application of infrared camouflage. The metasurface, with a total thickness of only 545 nm, consists of a Bi micro-disk array and a continuous ZnS and Ti film beneath it. Unlike conventional metal-based metasurface design, our approach leverages the unique optical properties of Bi, achieving an average emissivity of 0.91 in the 5-8 μm non-atmospheric transparency window. Experimental results indicate that the metasurface emitter achieves lower radiation and actual temperatures compared to those observed in comparative experiments, highlighting its superior energy dissipation and thermal stability. The metasurface offers advantages such as structural simplicity, cost-effectiveness, angular insensitivity, and deep-subwavelength features, rendering it suitable for a range of applications including military camouflage and anti-counterfeiting, with potential for broad deployment in infrared technologies.

UV-Vis-NIR Broadband Dual-Mode Photodetector Based on Graphene/InP Van Der Waals Heterostructure

Dual-mode photodetectors (DmPDs) have attracted considerable interest due to their ability to integrate multiple functionalities into a single device. However, 2D material/InP heterostructures, which exhibit built-in electric fields and rapid response characteristics, have not yet been utilized in DmPDs. In this work, we fabricate a high-performance DmPD based on a graphene/InP Van der Waals heterostructure in a facile way, achieving a broadband response from ultraviolet-visible to near-infrared wavelengths. The device incorporates two top electrodes contacting monolayer chemical vapor deposition (CVD) graphene and a bottom electrode on the backside of an InP substrate. By flexibly switching among these three electrodes, the as-fabricated DmPD can operate in a self-powered photovoltaic mode for energy-efficient high-speed imaging or in a biased photoconductive mode for detecting weak light signals, fully demonstrating its multifunctional detection capabilities. Specifically, in the self-powered photovoltaic mode, the DmPD leverages the vertically configured Schottky junction to achieve an on/off ratio of 8 × 103, a responsivity of 49.2 mA/W, a detectivity of 4.09 × 1011 Jones, and an ultrafast response, with a rising time (τr) and falling time (τf) of 2.8/6.2 μs. In the photoconductive mode at a 1 V bias, the photogating effect enhances the responsivity to 162.5 A/W. This work advances the development of InP-based multifunctional optoelectronic devices.

Switchable Multi-Spectral Electromagnetic Defense in the Ultraviolet, Visible, Infrared, Gigahertz, and Terahertz Bands Using a Magnetically-Controllable Soft Actuator

Traditional passive single-spectrum electromagnetic defense materials are inadequate to defend against complex multispectral electromagnetic threats. Herein, a bilayer heterofilm (BLH film)-based magnetically controllable soft actuator (MCSA), comprising a defense unit and a drive unit, is constructed. The defense unit offers multispectral electromagnetic protection, while the drive unit enables active defense via magnetic actuation. The synergy allows the MCSA to provide intelligent, switchable electromagnetic defense from ultraviolet to terahertz spectra. The BLH film exhibits the lowest infrared emissivity of 0.04 at 14 μm and an average of 0.16 at 8-14 μm, outperforming comparable composites while integrating radiation energy management for enhanced overall protection. It also demonstrates complete blocking of ultraviolet and visible light (320-780 nm), demonstrating zero transmission. Furthermore, the MCSA can be modulated between open and closed states by applying a magnetic field, facilitating a seamless transition between full-band transparency and full-band defense modes. To expand electromagnetic defense applications, a multilayer gradient impedance matching (M-BLH-300) absorber based on the BLH film is fabricated for stealth in microwave bands, achieving a strong reflection loss of -26.7 dB with an effective absorption bandwidth of 4.85 GHz. Notably, the M-BLH-300 absorber retains excellent performance when extended to the terahertz frequency range and further demonstrates its suitability for multispectrum (from ultraviolet to terahertz) defense. In short, this innovative design concept of combining multispectral defense with intelligent switches will guide the development of next-generation advanced electromagnetic defense systems.

High-Temperature Stealth Across Multi-Infrared and Microwave Bands with Efficient Radiative Thermal Management

High-temperature stealth is vital for enhancing the concealment, survivability, and longevity of critical assets. However, achieving stealth across multiple infrared bands-particularly in the short-wave infrared (SWIR) band-along with microwave stealth and efficient thermal management at high temperatures, remains a significant challenge. Here, we propose a strategy that integrates an IR-selective emitter (Mo/Si multilayer films) and a microwave metasurface (TiB2-Al2O3-TiB2) to enable multi-infrared band stealth, encompassing mid-wave infrared (MWIR), long-wave infrared (LWIR), and SWIR bands, and microwave (X-band) stealth at 700 °C, with simultaneous radiative cooling in non-atmospheric window (5-8 μm). At 700 °C, the device exhibits low emissivity of 0.38/0.44/0.60 in the MWIR/LWIR/SWIR bands, reflection loss below - 3 dB in the X-band (9.6-12 GHz), and high emissivity of 0.82 in 5-8 μm range-corresponding to a cooling power of 9.57 kW m-2. Moreover, under an input power of 17.3 kW m-2-equivalent to the aerodynamic heating at Mach 2.2-the device demonstrates a temperature reduction of 72.4 °C compared to a conventional low-emissivity molybdenum surface at high temperatures. This work provides comprehensive guidance on high-temperature stealth design, with far-reaching implications for multispectral information processing and thermal management in extreme high-temperature environments.

A Triband Metasurface Covering Visible, Midwave Infrared, and Long-Wave Infrared for Optical Security

The independent manipulation of light across multiple wavelength bands provides new opportunities for optical security. Although dual-band optical encryption methods in the visible (VIS) and infrared bands have been developed, achieving synchronized and synergistic optical security across the VIS, midwave infrared (MWIR), and long-wave infrared (LWIR) bands remains a significant challenge. Here, we experimentally demonstrate a triband metasurface that covers the VIS, MWIR, and LWIR bands. While VIS imaging is achieved by structural color, MWIR, and LWIR imaging are achieved by selective emissivity structures, with MWIR/LWIR emissivities in the MWIR imaging region of 0.81/0.17, and in the LWIR imaging region of 0.21/0.83. Importantly, the MWIR and LWIR information is completely hidden in the VIS band. We also validate the ability of metasurface to encode complex information and information-misleading encryption. This work introduces new approaches for enhancing optical security and holds significant potential for applications such as anticounterfeiting and thermal camouflage.

Cephalopod-Inspired MXene-Integrated Mechanochromic Cholesteric Liquid Crystal Elastomers for Visible-Infrared-Radar Multispectral Camouflage

Multispectral camouflage materials that provide adaptable features across a wide spectrum, from visible light to radar frequencies, play a vital role in sophisticated multi-band electromagnetic (EM) applications. However, conventional single-band stealth is difficult to align with the growing demand for multi-band compatibility and intelligent adaptation. Herein, we report the design and synthesis of cephalopod-inspired MXene-integrated cholesteric liquid crystal elastomers (MXene-CLCEs) with multispectral camouflage capability, which was fabricated through in situ thiol-acrylate Michael addition and free-radical photopolymerization of CLCE precursor and isocyanate-mediated robust covalent chemical bonding of MXene nanocoating at the interface. The resulting MXene-CLCE exhibits dynamic structural color changes, tunable infrared radiation, and switchable microwave shielding across wide ranges upon mechanical stretching, with its infrared stealth and microwave shielding properties being realized through the reconfiguration of surface morphology from planar to cracked states via mechanical actuation. A visible-to-infrared camouflage octopus-patterned MXene-CLCE is demonstrated to achieve a stealth effect across the visible-infrared spectrum upon mechanical stretching. As an illustration, proof-of-concept pneumatic-driven octopus-inspired soft models are demonstrated, which enables dynamic visible-infrared camouflage and microwave shielding switching between two compatible states. The research herein can offer new perspectives on the development of bioinspired smart camouflage materials and their application in various emerging fields such as smart optical stealth, dynamic thermal management, and switchable electromagnetic devices.

Optical transparent metamaterial emitter with multiband compatible camouflage based on femtosecond laser processing

Infrared (IR) camouflage has garnered growing attention with progress in IR detection technology. The emergence of metamaterial with powerful electromagnetic field regulation ability provides an effective solution for thermal emission manipulation in IR camouflage. However, the intricated micro/nano machining technology of metamaterial greatly limits its moving toward practical application, and single-band IR camouflage makes it difficult to resist multiband cooperative detection systems. Here, a flexible, fine, and mask-free femtosecond laser direct writing (FsLDW) technology was introduced to pattern on ultra-thin metals. Based on this efficient technique, the optically transparent metamaterial emitter with multiband compatible camouflage is fabricated. The emitter is demonstrated to achieve high reflectance (R 3-5 µm = 0.79 and R 8-14 µm = 0.70) in the dual-band atmospheric window and low reflectance (R 1.06 µm = 0.3, R 1.55 µm = 0.1) for IR and laser stealth. In addition, the high emissivity (ɛ 5-8 µm = 0.64) for the nonatmospheric window effectively dissipates the accumulated heat, showing promising prospects in radiative cooling by comparison with Ag at the same heating power. This work offers a clue for coordinated control of multiband electromagnetic waves and heat through simple structural design, which is expected to promote its camouflage applications and thermal management in the military.

Wafer-Scale Transfer and Integration of Tungsten-Doped Vanadium Dioxide Films

Modern optoelectronic devices trend toward greater flexibility, wearability, and multifunctionality, demanding higher standards for fabrication and operation temperatures. Vanadium dioxide (VO2), with its metal-insulator transition (MIT) at 68 °C, serves as a crucial functional layer in many optoelectronic devices. However, VO2 usually needs to grow at >450 °C in an oxygen-containing atmosphere and to function across its MIT temperature, leading to low compatibility with most optoelectronic devices, especially on flexible substrates. In this work, we report a layer-by-layer transfer method of wafer-scale tungsten-doped VO2 films, which enables sequential integration of the VO2 films with low MIT temperatures (down to 40 °C) onto arbitrary substrates. Notably, by stacking multiple VO2 films with different doped levels, a quasi-gradient-doped VO2 architecture can be achieved, effectively broadening the MIT temperature window and reducing the hysteresis of VO2. These integrated VO2 films find a wide scope of applications in flexible temperature indicator strips, infrared camouflage devices, nonreciprocal ultrafast light modulators, and smart photoactuators. Our work promotes the development of more flexible and tunable optoelectronic devices integrated with VO2.

Low-Temperature IR Camouflage Materials by Dual Resonances for Enhanced Thermal Management without Energy Consumption

Due to the critical importance of carbon neutrality for the survival of humanity, passive thermal management, which manages thermal energy without additional energy consumption, has become increasingly attractive. Camouflage materials offer a promising solution for passive thermal management, as they can dissipate heat through thermal radiation, reducing the need for energy-intensive cooling systems. However, developing effective infrared (IR) camouflage solutions for low-temperature environments and small-sized applications remains a challenge because the low temperatures limit the ability to dissipate radiative energy from the surface. Moreover, conventional IR camouflage materials, typically optimized for single band (5-8 μm), face significant limitations in energy dissipation at lower temperatures, which requires a novel way to increase the energy dissipation without the additional energy consumption. Herein, we present a novel low-temperature IR camouflage material (LICM) designed to address these challenges by employing dual-band resonances in the nondetection bands, 5-8 and 14-20 μm based on the atmospheric transmittance. LICM demonstrated an increase in energy dissipation of 273 and 167% at 250 and 350 K, respectively than the conventional IR camouflage materials. Despite the enhanced dissipation, the LICM maintained an IR signature reduction of around 10% of blackbody radiation, ensuring effective IR camouflage. Thermographic measurements using an LWIR camera (7.5-14 μm) further demonstrated the LICM's superior IR camouflage performance. This dual-band resonance design not only extends IR camouflage to low-temperature environments but also facilitates significant energy savings, making it a key ingredient for broad-scale deployment in areas such as energy conversion, aerospace, and sustainable thermal management technologies.

A Rapidly Assembled and Camouflage-Monitoring-protection Integrated Modular Unit

Optical-electromagnetic compatible devices are urgently required in intelligent building monitors and cross-band protection. Meanwhile, the insufficient systematicness and semi-empirical attempts significantly limit the prosperity of cross-band materials, causing enormous challenges for deviceization and material database construction. Herein, the systematical component-deviceization-machine learning prediction-array construction strategy is attempted to solve the bottleneck issues. A luminance-triggered camouflage-monitoring-protection triune integrated modular unit (IMU) is hierarchically encapsulated to simultaneously achieve efficient anti-electromagnetic interference (EMI), light-absorbing, quick gradient-colorization response. Moreover, an illumination intensity dataset and a surrogate model based on fully connected neural network fitting (FCNN-fitting) are constructed, which accurately predicts the light-absorbing property of IMUs and can be instructional for material selection. The IMUs are specifically assembled into a 4*4 array, aiming at multi-scenario application of programmable display, camouflage pattern, surface conformality, and rapid replaceability. This work paves the path and provides a promising strategy for optical-electromagnetic compatibility and material genetics-deviceization-array systematization.

Adaptive Radiative Thermal Management Using Transparent, Flexible Ag Nanowire Networks

Effective heat management is critical for improving energy efficiency and minimizing environmental impact. Passive radiative heat management systems rely on specific materials and design configurations to naturally modulate temperature, enhance system reliability, and decrease operational costs by modulating infrared light. However, their static nature proves insufficient in dynamic settings experiencing significant temperature fluctuations. Adaptive radiative thermal management systems offer real-time heat exchange control, optimizing performance in varying conditions. However, such systems often interfere with the visible light response of the material, restricting application. Here, we present an adaptive thermal heat management system based on Ag nanowire (AgNW) networks on polydimethylsiloxane (PDMS). The AgNW network functions like a Faraday cage, with critical dimensions that do not interfere with visible light while effectively interacting with infrared light. Mechanical actuation enables over 40% modulation of thermal infrared light, leading to a perceived temperature difference of 6 °C when observed with a thermal camera relative to a 100 °C heat source.

Multifunctional metasurface for multispectral compatible camouflage of laser and infrared with thermal management

Multispectral compatible camouflage has attracted widespread attention due to the rapid development of various detection technologies. This work presents a multifunctional metasurface that is compatible with laser stealth, infrared shielding, and the thermal management function. To achieve laser stealth, the metasurface is designed as a metal-insulator-metal (MIM) structure for high absorption of laser lights at 1.06 and 1.54 µm, with absorption rates of 97.7 and 95.9%, respectively. Also, the metasurface is designed to minimize the specular reflectance of a 10.6 µm laser light based on the phase cancellation principle. To achieve infrared stealth, the proposed metasurface has achieved an ultralow emissivity in the atmosphere window, with an average emissivity of 0.04 in the 3-5 µm range and 0.11 in the 8-14 µm range. Additionally, the thermal management function is achieved by using the high absorption property of the metasurface in the non-atmospheric window (5-8 µm), which further improves the stealth performance in the infrared band. This work provides a novel, to the best of our knowledge, strategy to realize multispectral compatible camouflage with the thermal management function by using a compact integrated metasurface, indicating that it has promising prospects in future high-performance compatible stealth applications.

Droplet-Pen Writing of Ultra-Uniform Graphene Pattern for Multi-Spectral Applications

Artificial optical patterns bring wide benefits in applications like structural color display, photonic camouflage, and electromagnetic cloak. Their scalable coating on large-scale objects will greatly enrich the multimodal-interactive society. Here, a droplet-pen writing (DPW) method to directly write multi-spectral patterns of thin-film graphene is reported. By amphiphilicity regulations of 2D graphene nanosheets, ultra-uniform and ultrathin films can spontaneously form on droplet caps and pave to the substrate, thus inducing optical interference. This allows the on-surface patterning by pen writing of droplets. Specifically, drop-on-demand thin films are achieved with millimeter lateral size and uniformity up to 97% in subwavelength thickness (<100 nm), corresponding to an aspect ratio of over 30 000. The pixelated thin-film patterns of disks and lines in an 8-inch wafer scale are demonstrated, which enable low-emittance structural color paintings. Furthermore, the applications of these patterns for dual-band camouflage and infrared-to-visible encryption are investigated. This study highlights the potential of 2D material self-assembly in the large-scale preparation and multi-spectral application of thin film-based optical patterns.

Functional Carbon Springs Enabled Dynamic Tunable Microwave Absorption and Thermal Insulation

Electromagnetic (EM) wave pollution and thermal damage pose serious hazards to delicate instruments. Functional aerogels offer a promising solution by mitigating EM interference and isolating heat. However, most of these materials struggle to balance thermal protection with microwave absorption (MA) efficiency due to a previously unidentified conflict between the optimizing strategies of the two properties. Herein, this study reports a solution involving the design of a carbon-based aerogel called functional carbon spring (FCS). Its unique long-range lamellar multi-arch microstructure enables tunable MA performance and excellent thermal insulation capability. Adjusting compression strain from 0% to 50%, the adjustable effective absorption bandwidth (EAB) spans up to 13.4 GHz, covering 84% of the measured frequency spectrum. Notably, at 75% strain, the EAB drops to 0 GHz, demonstrating a novel "on-off" switchability for MA performance. Its ultralow vertical thermal conductivity (12.7 mW m-1 K-1) and unique anisotropic heat transfer mechanism endow FCS with superior thermal protection effectiveness. Numerical simulations demonstrate that FCS outperforms common honeycomb structures and isotropic porous aerogels in thermal management. Furthermore, an "electromagnetic-thermal" dual-protection material database is established, which intuitively demonstrates the superiority of the solution. This work contributes to the advancement of multifunctional MA materials with significant potential for practical applications.

Electrochemically-Switched Microwave Response of MXene in Organic Electrolyte

The increasingly complex electromagnetic (EM) environment necessitates advanced electrically controllable electromagnetic interference (EMI) shielding materials that can adapt to varying EM conditions. This study develops a flexible electrochemically tunable EMI shielding device based on ultrathin Ti3C2Tx MXene films, exhibiting reversible shielding effectiveness (SE) modulation from 18.9 to 26.2 dB in X band at 0.1 and -1.5 V. Unlike the previously reported mechanism relying on interlayer spacing adjustments, the work leverages transformations of charging state and surface chemistry for tunability during the electrochemical process. The Ti3C2Tx flake size is also evidenced to play a crucial role, with smaller flakes offering higher absorption modulation despite lower SE modulation, enabling the device with high designability. When integrated with Salisbury screen structure, the device achieves adjustable absorption from 93.560% at 0.1 V to 99.996% at -1 V, showing a tunable reflection suppression ratio up to 32 dB with an effective bandwidth of 4.2 GHz. Additionally, incorporating resonant cavity structure enables absorption-dominated (over 90%) microwave-responsive switching at 0.1 and -1.5 V. This work highlights significant potential of adaptive EMI shielding materials for applications in smart electronic protection, EM switch, and radar camouflage.

Flexible Meta-Tape with Wide Gamut, Low Lightness and Low Infrared Emissivity for Visible-Infrared Camouflage

Full-spectral optical camouflage is of broad interest and in urgent demand because of everlasting safety pursuit in modern society. However, the widely existing dim scenarios call for not only broadband low thermal detectivity but also wide-gamut camouflaging colors with both low lightness and minimal chromatism. Here, a tape-like metamaterial (meta-tape) with broad spectral manipulation bandwidth from visible to mid-infrared is demonstrated. The ultrathin meta-tapes can exhibit different colors with wide gamut and low lightness from 20 to 40, enabling low color difference under various backgrounds down to 1.2 L*a*b*. The infrared emissivity is simultaneously suppressed down to 3.8% across 3 - 14 µm. The outstanding optical performances are well preserved under various mechanical and thermal stability tests. The pronounced multispectral camouflage, combined with flexible and robust tape-like nature, makes the meta-tape a promising solution for VIS-IR compatible camouflage in diverse scenarios.

Epsilon-near-zero thin films in a dual-functional system for thermal infrared camouflage and thermal management within the atmospheric window

Thermal infrared camouflage aims to reduce the detectability of a target using thermal imaging devices. Given the typically high thermal emissivity in everyday environments, the thermal emissivity of the background environment must be considered. The conventional low-emissivity strategy for thermal camouflage is only effective for targets at extremely high temperatures (>350 °C), making it unsuitable for applications near room-to-medium-high temperature range (<350 °C). In this study, we introduce metallic glass into infrared thermal camouflage technology, exploiting its adjustable emissivity to accommodate diverse infrared thermal camouflage scenarios. Moreover, we combined metallic glass with the Berreman mode of epsilon-near-zero (ENZ) thin films (SiO2, Al2O3, and TiO2) for the first time. In the long wave infrared (LWIR, 8-14 μm) regions, the small viewing angle exhibits the optical properties of metallic glasses, while the large viewing angle (above 45°) provides high thermal emissivity in transverse-magnetic (TM) polarization. A thermal management function was provided without affecting the thermal camouflage performance. The cooling power exhibited by ENZ thin films on metallic glass surpassed that of the conventional low-emissivity strategy for thermal camouflage by a factor of 1.79. Furthermore, the thermal images indicated over 97% similarity in thermal radiation between the target and background environments. We developed a dual-function system for infrared camouflage and thermal management within an identical wavelength region of the atmospheric window.

Detection and Anti-Detection with Microwave-Infrared Compatible Camouflage Using Asymmetric Composite Metasurface

Detection and anti-detection with multispectral camouflage are of pivotal importance, while suffer from significant challenges due to the inherent contradiction between detection and anti-detection and conflict microwave and infrared (IR) stealth mechanisms. Here, a strategy is proposed to asymmetrically control transmitted microwave wavefront under radar-IR bi-stealth scheme using composite metasurface. It is engineered composed of infrared stealth layer (IRSL), microwave absorbing layer (MAL), and asymmetric microwave transmissive structure (AMTS) with polarization conversion from top to bottom. Therein, IR emissivity, microwave reflectivity, and transmissivity are simultaneously modulated by elaborately designing the filling ratio of ITO square patches on IRSL, which ensures both efficient microwave transmission and IR camouflage. Furthermore, full-polarized backward microwave stealth is achieved on MAL by transmitting and absorbing microwaves under x- and y- polarization, respectively, while forward wavefront is controlled by precise curvature phase compensation on AMTS according to ray-tracing technology. For verification, a proof-of-concept metadevice is numerically and experimentally characterized. Both results coincide well, demonstrating spiral detective wavefront manipulation under y-polarized forward wave excitation while effective reduction of radar cross section within 8-18 GHz and low IR emissivity (<0.3) for backward detection. This strategy provides a new paradigm for integration of detection and anti-detection with multispectral camouflage.

Near-Field-Regulated Ultrafast Laser Supra-Wavelength Structuring Directly on Ultrahard Metallic Glasses

The ultrafast-laser-matter interactions enable "top-down" laser surface structuring, especially for materials difficult to process, with "bottom-up" self-organizing features. The subwavelength scenarios of laser-induced structuring are improved in defects and long-range order by applying positive/negative feedbacks. It is still hardly reported for supra-wavelength laser structuring more associated with complicated thermo/hydro-dynamics. For the first time to the knowledge, the near-field-regulated ultrafast-laser lithography of self-arrayed supra-wavelength micro/nano-pores directly on ultra-hard metallic glass is developed here. The plasmonic hot spots on pre-structures, as the positive feedback, clamped the lateral geometries (i.e., position, size). Simultaneously, it drilled and self-organized into micro/nano-pore arrays by photo-dynamic plasma ablation and Marangoni removal confined under specific femtosecond-laser irradiation, as the negative feedback. The mechanisms and finite element modeling of the multi-physical transduction (based on the two-temperature model), the far-field/near-field coupling, and the polarization dependence during laser-matter interactions are studied. Large-area micro/nano-pore arrays (centimeter scale or larger)  are manufactured with tunable periods (1-5 µm) and geometries (e.g., diameters of 500 nm-6 µm using 343, 515, and 1030 lasers, respectively). Consequently, the mid/far-infrared reflectivity at 2.5-6.5 µm iss decreased from ≈80% to ≈5%. The universality of multi-physical coupling and near-field enhancements makes this approach widely applicable, or even irreplaceable, in various applications.

Highly circularly polarized and coherent thermal emission based on chiral quasi bound states in the continuum

Polarization, temporal coherence, and spatial coherence are crucial for far-field thermal emission. However, achieving chiral thermal emission with both ultra-narrow bandwidth and ultrahigh directionality remains a challenge. In this study, we address this problem by combining the principles of band folding and chiral quasi bound states in the continuum. The demonstrated thermal emitter, a tri-layered structure consisting of a planar chiral silicon metasurface, a silica spacer, and a reflecting gold film, numerically achieves an emissivity circular dichroism of 0.984, a full width at half maximum of 1.6 nm, and a divergence angle of 1° at wavelength 1170 nm, surpassing the state-of-the-art thermal emitters. Our finding provides a new, to our knowledge, approach for designing chiral thermal emitters, which may find use in the areas of thermal lighting, infrared camouflage, thermal imaging, and infrared sensing.

Three peak metamaterial broadband absorbing materials based on ZnSe-Cr-InAs stacked disk arrays

Metamaterial absorbers show great potential in many scientific and technological applications by virtue of their sub-wavelength and easy-to-adjust structure, with bandwidth as an important standard to measure the performance of the absorbers. In this study, our team designed a new broadband absorber, which consists of an indium arsenide (InAs) disk at the top, a zinc selenide (ZnSe)-chromium (Cr) stacked disk in the middle and a metal film at the bottom. Simulation results show that the absorber has remarkable absorptivity properties in the mid-long infrared band. In a wavelength range of 5.71-16.01 μm, the average absorptivity is higher than 90%. In the band of 5.86-15.49 μm, the absorptivity is higher than 95%. By simulating the electromagnetic field diagram at each resonant frequency, the reason for high broadband absorptivity is obtained. We also constructed Poynting vector diagrams to further elucidate this phenomenon. Next, we analyzed the influence of different materials and structural parameters on absorptivity properties and tested spectral response at different polarization angles and oblique incidence of the light source in the TM and TE modes. When the source is normally incident, the absorber shows polarization insensitivity. When the angle is 40°, absorptivity is still high, indicating that the absorber also possesses angle insensitivity. The broadband absorber proposed by us has good prospects in infrared detection and thermal radiators.

Magneto-Dielectric Synergy and Multiscale Hierarchical Structure Design Enable Flexible Multipurpose Microwave Absorption and Infrared Stealth Compatibility

Developing advanced stealth devices to cope with radar-infrared (IR) fusion detection and diverse application scenarios is increasingly demanded, which faces significant challenges due to conflicting microwave and IR cloaking mechanisms and functional integration limitations. Here, we propose a multiscale hierarchical structure design, integrating wrinkled MXene IR shielding layer and flexible Fe3O4@C/PDMS microwave absorption layer. The top wrinkled MXene layer induces the intensive diffuse reflection effect, shielding IR radiation signals while allowing microwave to pass through. Meanwhile, the permeable microwaves are assimilated into the bottom Fe3O4@C/PDMS layer via strong magneto-electric synergy. Through theoretical and experimental optimization, the assembled stealth devices realize a near-perfect stealth capability in both X-band (8-12 GHz) and long-wave infrared (8-14 µm) wavelength ranges. Specifically, it delivers a radar cross-section reduction of - 20 dB m2, a large apparent temperature modulation range (ΔT = 70 °C), and a low average IR emissivity of 0.35. Additionally, the optimal device demonstrates exceptional curved surface conformability, self-cleaning capability (contact angle ≈ 129°), and abrasion resistance (recovery time ≈ 5 s). This design strategy promotes the development of multispectral stealth technology and reinforces its applicability and durability in complex and hostile environments.

Multifunctional Radiation Conditioning Emitter for Laser and Infrared with Adaptive Radiative Cooling

With the development of technology, multifunctional multiband emitters have been paid much attention due to their wide range of applications, such as LIDAR detection, spectroscopic sensing, and infrared thermal management. However, the development of such emitters is impeded by incompatible structural requirements of different electromagnetic wavebands. Here, we demonstrate coupled modulation between near-infrared (NIR) laser-wavelength and long-wavelength-infrared by constructing a multifunctional emitter (MFE) with a structure of Al/HfO2/VO2, utilizing the phase transition of VO2. The MFE displays excellent thermal modulation capability within the 8-14 μm range, achieving a thermal insulation effect (ε8-14 μm = 0.18) at low temperatures, and heat dissipation effect (ε8-14 μm = 0.64) at high temperatures. The MFE's radiation power regulation capability is 145.06 W m-2 between a temperature of 0 to 60 °C. Moreover, the MFE possesses a large reflectivity modulation value of 0.78 at NIR laser-wavelength (1.06 μm) with a short phase transition time of 1003 ms under 3 W cm-2 laser irradiation. This study provides a guideline for the coordinated control of electromagnetic waves and intelligent collaborative thermal management through simple structural design, thus, having broad implications in energy saving and thermal information processing.

Wetting Behavior-Induced Interfacial transmission of Energy and Signal: Materials, Mechanisms, and Applications

Wetting behaviors can significantly affect the transport of energy and signal (E&S) through vapor, solid, and liquid interfaces, which has prompted increased interest in interfacial science and technology. E&S transmission can be achieved using electricity, light, and heat, which often accompany and interact with each other. Over the past decade, their distinctive transport phenomena during wetting processes have made significant contributions to various domains. However, few studies have analyzed the intricate relationship between wetting behavior and E&S transport. This review summarizes and discusses the mechanisms of electrical, light, and heat transmission at wetting interfaces to elucidate their respective scientific issues, technical characteristics, challenges, commonalities, and potential for technological convergence. The materials, structures, and devices involved in E&S transportation are also analyzed. Particularly, harnessing synergistic advantages in practical applications and constructing advanced, multifunctional, and highly efficient smart systems based on wetted interfaces is the aim to provide strategies.

PISC-Net: A Comprehensive Neural Network Framework for Predicting Metasurface Infrared Emission Spectra

Multifunctional metasurfaces have exhibited extensive potential in various fields, owing to their unparalleled capacity for controlling electromagnetic wave characteristics. The precise resolution is achieved through numerical simulation in conventional metasurface design methodologies. Nevertheless, the simulations using these approaches are inherently computationally costly. This paper proposes the Physical Insight Self-Correcting Convolutional Network (PISC-Net), which enables rapid prediction of infrared radiation spectra of metasurfaces with remarkable generalization capacity. In contrast to preceding prediction networks, we have enhanced the cognitive ability of the network to recognize physical mechanisms by designing parameter-communication modules and integrating a priori knowledge grounded in the parameter association mechanism. Additionally, we proposed an effective strategy for constructing data sets that facilitate precise tuning of absorption bands in the entire spectral range (3-14 μm) and serves to reduce the costs associated with data set development. Transfer learning is employed to obtain precise predictions for large-period metasurfaces from limited data sets. This approach demonstrates that a network trained exclusively on simulation data could predict experimental outcomes accurately, as proved by the comparative analysis between simulation, experimental testing, and prediction results. The average mean square error is less than 4%.

A Mid-Infrared Perfect Metasurface Absorber with Tri-Band Broadband Scalability

Metasurfaces have emerged as a unique group of two-dimensional ultra-compact subwavelength devices for perfect wave absorption due to their exceptional capabilities of light modulation. Nonetheless, achieving high absorption, particularly with multi-band broadband scalability for specialized scenarios, remains a challenge. As an example, the presence of atmospheric windows, as dictated by special gas molecules in different infrared regions, highly demands such scalable modulation abilities for multi-band absorption and filtration. Herein, by leveraging the hybrid effect of Fabry-Perot resonance, magnetic dipole resonance and electric dipole resonance, we achieved multi-broadband absorptivity in three prominent infrared atmospheric windows concurrently, with an average absorptivity of 87.6% in the short-wave infrared region (1.4-1.7 μm), 92.7% in the mid-wave infrared region (3.2-5 μm) and 92.4% in the long-wave infrared region (8-13 μm), respectively. The well-confirmed absorption spectra along with its adaptation to varied incident angles and polarization angles of radiations reveal great potential for fields like infrared imaging, photodetection and communication.

Graphene-Based Tunable Polarization Conversion Metasurface for Array Antenna Radar Cross-Section Reduction

A graphene-based tunable polarization conversion metasurface (PCM) was designed and analyzed for the purpose of reducing the radar cross-section (RCS) of array antennas. The metasurface comprises periodic shuttle-shaped metal patches, square-patterned graphene, and inclined grating-patterned graphene. By adjusting the Fermi energy levels of the upper (μ1) and lower (μ2) graphene layers, different states were achieved. In State 1, with μ1 = 0 eV and μ2 = 0.5 eV, the polarization conversion ratio (PCR) exceeded 0.9 in the bandwidths of 1.65-2.19 THz and 2.29-2.45 THz. In State 2, with μ1 = μ2 = 0.5 eV, the PCR was greater than 0.9 in the 1.23-1.85 THz and 2.24-2.60 THz bands. In State 3, with μ1 = μ2 = 1 eV, the PCR exceeded 0.9 in the 2.56-2.75 THz and 3.73-4.05 THz bands. By integrating the PCM with the array antenna, tunable RCS reduction was obtained without affecting the basic radiation functionality of the antenna. In State 1, RCS reduction was greater than 10 dB in the 1.60-2.43 THz and 3.63-3.72 THz frequency ranges. In State 2, the RCS reduction exceeded 10 dB in the 2.07-2.53 THz, 2.78-2.98 THz, and 3.70-3.81 THz bands. In State 3, RCS reduction was greater than 10 dB in the 1.32-1.43 THz, 2.51-2.76 THz, and 3.76-4.13 THz frequency ranges. This polarization conversion metasurface shows significant potential for applications in switchable and tunable antenna RCS reduction.

Simultaneous thermal camouflage and radiative cooling for ultrahigh-temperature objects using inversely designed hierarchical metamaterial

Sophisticated infrared detection technology, operating through atmospheric transmission windows (usually between 3 and 5 μm and 8-13 μm), can detect an object by capturing its emitted thermal radiation, posing a threat to the survival of targeted objects. As per Wien's displacement law, the shift of peak wavelength towards shorter wavelengths as blackbody temperature rises, underscores the significance of the 3-5 μm range for ultra-high temperature objects (e.g., at 400 °C), emphasizing the crucial need to control this radiation for the objects' viability. Additionally, effective heat management is essential for ensuring the consistent operation of these ultrahot entities. In this study, based on a database with high-temperature resist materials, we introduced a material-informatics-based framework aimed at achieving the inverse design of simultaneous thermal camouflage (low emittance in the 3-5 μm range) and radiative cooling (high emittance in the non-atmospheric window 5-8 μm range) tailored for ultrahigh-temperature objects. Utilizing the transfer matrix method to calculate spectral properties and employing the particle swarm optimization algorithm, two optimized multilayer structures with desired spectral characteristics are obtained. The resulted structures demonstrate effective infrared camouflage at temperatures up to 250 °C and 500 °C, achieving reductions of 86.7 % and 63.7 % in the infrared signal, respectively. At equivalent heating power densities applied to the structure and aluminum, structure 1 demonstrates a temperature reduction of 29.4 °C at 0.75 W/cm2, while structure 2 attains a temperature reduction of 57.5 °C at 1.50 W/cm2 compared to aluminum, showcasing enhanced radiative cooling effects. This approach paves the way for attenuating infrared signals from ultrahigh-temperature objects and effectively managing their thermal conditions.

Multispectral metal-based electro-optical metadevices with infrared reversible tunability and microwave scattering reduction

The demand for advanced camouflage technology is increasing in modern military warfare. Multispectral compatibility and adaptive capabilities are increasingly desired features in camouflage materials. However, due to the strong wavelength dependence and limited tunability of electromagnetic wave responses, achieving simultaneous multispectral compatibility and adaptive capability in a single structure or device remains a challenge. By integrating coding metamaterials with infrared (IR) electrochromic devices, we demonstrate a highly integrated multispectral metal-based electro-optical metadevice. The fabricated metadevices enable the reversible tunability of IR emissivity (0.58 at 3-5 µm, 0.50 at 7.5-13 µm) and wideband microwave scattering reduction (>10 dB at 10-20 GHz). The excellent integration performance is attributed to the remarkable electromagnetic control capabilities of the coding metamaterials in a chessboard-like configuration and the IR electrochromic devices based on metal reversible electrodeposition. Furthermore, the monolithic integrated design with shared barium fluoride substrate and electrodes allows the metadevices to have a simple architecture, and the careful design avoids coupling between functions. Our approach is general enough for the design of various electrochromic devices and metamaterials for multispectral camouflage, offering valuable insights for the development of advanced adaptive multispectral camouflage systems.

Visible-infrared compatible and independent camouflage with multicolor patterns and tunable emissivity

With the rapid development and wide application of visible (VIS) and infrared (IR) detections, it is necessary to explore visible-infrared (VIS-IR) compatible camouflage. Here, we report a VIS-IR compatible and independent camouflage device which is composed of the upper IR-transparent VIS-color-patterned layer and the lower electrochromic IR layer. The upper layer has amorphous photonic structure of polystyrene nanospheres (PSNSs). By customizing the PSNS size, various colors can be realized for VIS camouflage. The lower electrochromic IR layer takes advantage of multiwall carbon nanotubes (MWCNTs) as the electrode as well as the IR active material. Experimental results reveal that different colors (including blue, green, and purple) have been obtained, and the IR emissivity can be electrically regulated from 0.43 to 0.9. Moreover, the prototype also exhibits good electrical stability as well as hydrophobic characteristic (the water contact angle of the outmost surface exceeds 120°). These output performances demonstrate the success of our design strategy for promoting the finding applied in camouflage fields as well as energy conservation fields.

Self-assembled skin-like metamaterials for dual-band camouflage

Skin-like soft optical metamaterials with broadband modulation have been long pursued for practical applications, such as cloaking and camouflage. Here, we propose a skin-like metamaterial for dual-band camouflage based on unique Au nanoparticles assembled hollow pillars (NPAHP), which are implemented by the bottom-up template-assisted self-assembly processes. This dual-band camouflage realizes simultaneously high visible absorptivity (~0.947) and low infrared emissivity (~0.074/0.045 for mid-/long-wavelength infrared bands), ideal for visible and infrared dual-band camouflage at night or in outer space. In addition, this self-assembled metamaterial, with a micrometer thickness and periodic through-holes, demonstrates superior skin-like attachability and permeability, allowing close attachment to a wide range of surfaces including the human body. Last but not least, benefiting from the extremely low infrared emissivity, the skin-like metamaterial exhibits excellent high-temperature camouflage performance, with radiation temperature reduction from 678 to 353 kelvin. This work provides a new paradigm for skin-like metamaterials with flexible multiband modulation for multiple application scenarios.

Multi-spectral compatible metasurface with low infrared emissivity, independent microwave complex-amplitude control, and high visible transparency

With the rapid development of communication technology and detection technology, it is difficult for devices operating in a single spectrum to meet the application requirements of device integration and miniaturization, resulting in the exploration of multi-spectrum compatible devices. However, the functional design of different spectra is often contradictory and difficult to be compatible. In this work, a transparent slit circular metasurface with a high filling ratio is proposed to achieve the compatibility of microwave, infrared and visible light. In the microwave, based on the Pancharatnam-Berry phase theory, the continuous amplitude and binary phase can be customized only by rotating the slit angle to achieve an Airy beam function at 8-12 GHz. In the infrared, the mean infrared emissivity is reduced to 0.3 at 3-14 µm by maintaining high conductive filling ratio, and in visible light, based on the transparency of materials, the mean transmittance can achieve 50% at 400-800 nm. All the results can verify the multi-spectral compatibility performance, which can also verify the validity of our design method. Importantly, the multi-spectral compatible metasurface contributes an option for multifunctional integration, which can be further applied in communication, camouflage, and other fields.

MXene-Enabled Pneumatic Multiscale Shape Morphing for Adaptive, Programmable and Multimodal Radar-infrared Compatible Camouflage

Achieving radar-infrared compatible camouflage with dynamic adaptability has been a long-sought goal, but faces significant challenges owing to the limited dispersion relations of conventional material systems operating in different wavelength ranges. Here, this work proposes the concept of pneumatic multiscale shape morphing and design a periodically arranged pneumatic unit consisting of MXene-based morphable conductors and intake platforms. During gas actuation, the morphable conductor transforms centimeter-scale 2D flat sheets into 3D balloon shapes to enhance microwave absorption behavior, and also reconfigures micrometer-scale MXene wrinkles into smooth planes in combination with cavity-induced low heat transfer to minimize infrared (IR) signatures. Through theory-guided reverse engineering, the final pneumatic matrix shows remarkable frequency tunability (2.64-18.0 GHz), moderate IR emissivity regulation (0.14 at 7-16.5 µm), rapid responsiveness (≈30 ms), wide-angle operation (>45°), and excellent environmental tolerance. Additionally, the multiplexed pneumatic matrix enables over 14 programmable coding sequences that independently alter thermal radiation without compromising radar stealth, and allows multimodal camouflage switching between three distinct compatible states. The approach may facilitate the evolution of camouflage techniques and electromagnetic functional materials toward multispectral, adaptability and intelligence.

Ultrawide Spectra Camouflage Coatings from Metallic Flake Powder

Ultrawide-spectra-compatible camouflage materials are imperative for military science and national security due to the continuous advancement of various sophisticated multispectral detectors. However, ultrawide spectra camouflage still has challenges, as the spectral requirements for different bands are disparate and even conflicting. This work demonstrates an ultrawide spectra camouflage material compatible with visible (VIS, 400-800 nm), infrared (IR, 3-5 and 8-14 μm), and microwave (S-Ku bands, 2-12 GHz). The carbon nanotubes adsorbed on porous anodic alumina/aluminum flake powder (CNTs@PAA/AFP) material for ultrawide spectra camouflage is composed of bioinspired porous alumina surface layers for low visible reflection and aluminum flake powder substrate for low infrared emissivity, while the surface of the porous alumina layers is loaded with carbon nanotubes for microwave absorption. Compared with previous low-emissivity materials, CNTs@PAA/AFP has omnidirectional low reflectance (Ravg = 0.29) and high gray scale (72%) in the visible band. Further, it exhibits low emissivity (ε3-5μm = 0.15 and ε8-14μm = 0.18) in the dual infrared atmospheric window, which reduces the infrared lock-on range by 59.6%/49.8% in the mid/far-infrared band at high temperatures (573 K). The infrared camouflage performance calculated from the radiation temperature of CNTs@PAA/AFP coatings is enhanced to over 65%, which is at least 4 times greater than that of its substrate. In addition, the CNTs@PAA/AFP coating achieves high microwave absorption (RLmin = -42.46 dB) and an effective absorption bandwidth (EAB = 7.43 GHz) in the microwave band (S-Ku bands) due to the enhancement of interfacial polarization and conductive losses. This study may introduce new insight and feasible methods for multispectral manipulation, electromagnetic signal processing, and thermal management via bioinspired structural design and fabrication.

Optically compatible infrared camouflage performance of ITO ink

With the rapid development of military reconnaissance technology, reconnaissance devices have been equipped with wideband reconnaissance ability, which imposes increased requirements on camouflage. Developing multiband camouflage materials with good compatibility has become increasingly important. Indium tin oxide (ITO), a transparent conductive oxide with good comprehensive photoelectric properties, exhibits different absorption, reflectivity, and transmission characteristics in different bands of electromagnetic waves. Therefore, ITO might be able to solve broadband and multiband camouflage problems effectively. In this paper, ITO is expressed as In32-xSnxO48. The energy band structure, optical properties, and infrared absorption spectra at different doping ratios of Sn (x = 0, 1, 2, 3) were obtained on the basis of first principle theory, and the camouflage mechanism of ITO in different electromagnetic wavebands was explored. Results demonstrated that when x = 3, specifically, when the doping ratio of Sn atoms was 9.375%, ITO had high transmission in the visible light band and infrared band reflectivity and can realize optically compatible infrared camouflage. In accordance with calculation results, ITO nanodispersion liquid (x = 3) was mixed with green camouflage coating added with some additives to prepare green ITO camouflage ink for silkscreen printing. The ink formed a camouflage protective ink coating after it was coated onto the surface of fabric through silkscreen printing. Results showed that the emissivity of the ITO ink coating decreased by more than 0.13 when its solid content reached 20%, and its camouflage performance in the visible light band was barely affected. The results of this research can guide the application of ITO materials in the field of camouflage.

Multifunctional integrated metamaterials for radar-infrared-visible compatible multispectral stealth

Metamaterials offer exciting opportunities for developing multispectral stealth due to their unique electromagnetic properties. However, currently transparent radar-infrared-visible compatible stealth metamaterials typically involve complex hierarchical designs, leading to thickness and transparency limitations. Here, we propose an integrated metamaterial for multispectral stealth with high transparency. Our design features an ITO/dielectric/ITO sandwich structure, with the upper-layer ITO acting as a resonator for broadband microwave absorption while maintaining a high filling ratio to suppress infrared (IR) radiation. Experimental results demonstrate excellent performance, with over 90% microwave absorption in 8-18 GHz, an IR emissivity of approximately 0.36 in 3-14 µm, an average optical transmittance of 74.1% in 380-800 nm, and a thickness of only 2.4 mm. With its multispectral compatibility, the proposed metamaterial has potential applications in stealth and camouflage fields.