Beyond the Visible: Bioinspired Infrared Adaptive Materials

Recent Advances in Spectrally Selective Daytime Radiative Cooling Materials

Daytime radiative cooling is an eco-friendly and passive cooling technology that operates without external energy input. Materials designed for this purpose are engineered to possess high reflectivity in the solar spectrum and high emissivity within the atmospheric transmission window. Unlike broadband-emissive daytime radiative cooling materials, spectrally selective daytime radiative cooling (SSDRC) materials exhibit predominant mid-infrared emission in the atmospheric transmission window. This selective mid-infrared emission suppresses thermal radiation absorption beyond the atmospheric transmission window range, thereby improving the net cooling power of daytime radiative cooling. This review elucidates the fundamental characteristics of SSDRC materials, including their molecular structures, micro- and nanostructures, optical properties, and thermodynamic principles. It also provides a comprehensive overview of the design and fabrication of SSDRC materials in three typical forms, i.e., fibrous materials, membranes, and particle coatings, highlighting their respective cooling mechanisms and performance. Furthermore, the practical applications of SSDRC in personal thermal management, outdoor building cooling, and energy harvesting are summarized. Finally, the challenges and prospects are discussed to guide researchers in advancing SSDRC materials.

Biomimetic Intelligent Thermal Management Materials: From Nature-Inspired Design to Machine-Learning-Driven Discovery

The development of biomimetic intelligent thermal management materials (BITMs) is essential for tackling thermal management challenges in electronics and aerospace applications. These materials possess not only exceptional thermal conductivity but also environmental compatibility. However, developing such materials necessitates overcoming intricate challenges, such as precise control over the material structure and optimization of the material's properties and stability. This review comprehensively overviews the research progress of BITMs, emphasizing the synergy between biomimetic design principles and artificial-intelligence-driven methodologies to enhance their performance. The unique nature-inspired structures are explored and valuable insights are provided into adaptive thermal management strategies, which can be further enhanced through data analytics and machine learning (ML). This review offers insights into overcoming design challenges and outlines future prospects for advanced BITMs by integrating ML and biomimetic design principles.

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.

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.

Customizable Single-Layer Programmable Deformation Hydrogel Robots Based on One-Time Fabricating with Near-Infrared-Triggered Responsiveness

Programmable deformation hydrogel robots have garnered significant attention in biomedical fields due to their ability to undergo large-scale reversible deformation. As clinical demand rises, there is a need for hydrogel robots that are easy to process and operate, and can undergo programmable deformation. Here, we propose a method to fabricate single-layer programmable deformation hydrogel robots in one step using a high-precision digital light processing 3D printing system. Two kinds of deformable elements with different structure distribution on the top and bottom sides are produced by using two kinds of focused light with varying intensities. By combining these deformable elements, we create four basic modules with different and fixed deformable shapes. The desired shape deformation in hydrogel robots can be achieved by programming the combination of these four basic modules. The hydrogel robots exhibit reversible repeat deformation under near-infrared light stimulation. We validate our approach by fabricating several scaffolds using combinations of the four basic modules, demonstrating the feasibility of programming deformation and the potential application of these scaffolds in pipeline movement. This research provides the feasibility for the simple programming deformation of hydrogel robots and offers a novel approach for fabricating programmable deformation hydrogel robots in biomedical fields.

Force-Trainable Liquid Crystal Elastomer Enabled by Mechanophore-Induced Radical Polymerization

In nature, organisms adapt to environmental changes through training to learn new abilities, offering valuable insights for developing intelligent materials. However, replicating this "adaptive learning" in synthetic materials presents a significant challenge. This study introduces a feasible approach to train liquid crystal elastomers (LCEs) by integrating a mechanophore tetraarylsuccinonitrile into their main chain, addressing the challenge of enabling synthetic materials to exchange substances with their environment. Inspired by biological training, the LCEs can self-strengthen and acquire new functionalities through mechanical stress-induced radical polymerization. The research not only enhances the mechanical performance of LCEs, but also endows them with the ability to learn properties such as flexibility, light responsiveness, and fluorescence. These advancements are crucial for overcoming the limitations of current materials, paving the way for the creation of advanced intelligent soft materials with autonomous self-improvement, akin to the adaptive skills of living organisms.

ATP-Exhausted Strategy Induced Anti-Tumor Low-Temperature Photothermal Therapy Based on Rare Earth Nanocrystals Modified Hollow Porous MnOx Nanozyme with TME-Activated NIR-II Imaging

Insufficient adenosine triphosphate (ATP) can reduce the synthesis of heat-stress-induced heat shock proteins (HSPs) to promote the efficiency of mild photothermal therapy (mPTT), thus the rational design of ATP-exhausted strategy based on nanotechnology is an effective approach to resuscitate mPTT. Herein, Nd3+ doped nanocrystals (NaYF4:Nd@CaF2, Nd-NCs) modified hollow mesoporous manganese oxide (H-MnOx) nanocomposite (H-MnOx@Nd-NCs, MN) is synthesized, and loaded with glucose transporters (GLUTs) inhibitor KL-11743, noted as MN-KL nanozyme. In tumor microenvironment (TME), MN-KL can react with overexpressed glutathione (GSH) to release KL-11743, which can suppress the synthesis of intracellular ATP at the source by blocking glucose uptake to inhibit HSPs expression, meanwhile, MN-KL catalyzes the production of ·O2 -/1O2/·OH and lipid peroxidation (LPO) to cleave existing HSPs. Through a two-pronged strategy with ATP inhibition and oxide accumulation, reducing the level of HSPs can be guaranteed for achieving efficient mPTT in both subcutaneous and in situ tumor models in mice. During this process, Nd-NCs can absorb near-infrared light and convert it into heat, and the quenched fluorescence of Nd-NCs by H-MnOx can be recovered through GSH-triggered biodegradation in tumors, thus the modification of Nd-NCs not only provides photothermal effect but also enables MN to own TME-activated fluorescence imaging.

Electrically Controlled Metal-Insulator Heterogeneous Evolution for Infrared Switch and Perfect Absorption

Active switching, which enables multifunctionality within a single optical component, is essential for reconfigurable infrared photonic systems such as radiation engineering, sensing, and communication. Metamaterials offer a solution but involve complex design and fabrication. A simpler approach with a planar layered structure becomes promising for offering economical manufacturing, easier integration, and scalability. However, it requires an active medium with giant tunability and effective modulation mechanisms. Here, an electrically controlled reversible infrared switching is demonstrated via a single layer of perovskite nickelate on an opaque substrate. Driven by the evolution of the refractive index during an electrically triggered proton-mediated metal-to-insulator transition, the device transforms from a high reflective (R ≈0.74) to a low reflective state (R ≈0.09) at λ = 7-10 µm. A temperature-independent perfect absorption (A > 0.99 at λ = 11.6-12.1 µm) emerges in the partially hydrogenated state with the mixture of the metal and insulator phases, which results in a modulation of emissivity ≈0.623 at λ = 7-14 µm. The switching behavior is tunable over a wide temperature and wavelength range, offering a versatile path for adaptive infrared applications.

Soft Matter Photonics: Interplay of Soft Matter and Light

The light-soft matter interaction and its applications form the foundation of Soft Matter Photonics, here termed "Soft Mattonics", positioning it as fertile ground for developing next-generation photonic technologies. Over the past few decades, this rapidly evolving field has achieved significant advancements, leading to successful applications across a wide range of disciplines, including optoelectronics, photonics, information technology, material science, robotics, biomedicine, and astronomy. In this Perspective, we provide an overview of Soft Mattonics, highlighting recent developments in light-controlled soft matter and their applications in light field manipulating. Additionally, we offer insights into future research directions for Soft Mattonics, with an emphasis on both foundational research and practical applications that will drive continued growth and innovation in this field.

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.

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.

Asymmetric Structural MXene/PBO Aerogels for High-Performance Electromagnetic Interference Shielding with Ultra-Low Reflection

Electromagnetic interference (EMI) shielding materials with low electromagnetic (EM) waves reflection characteristics are ideal materials for blocking EM radiation and pollution. Materials with low reflectivity must be constructed using materials with excellent EM waves absorption properties. However, materials simultaneously possessing both low reflectivity and excellent EMI shielding performance remain scarce, consequently, multilayer structures need to be developed. Poly(p-phenylene-2,6-benzobisoxazole) nanofibers (PNF) are prepared by deprotonation. PNF are combined with MXene and heterostructure MXene@Ni prepared by in-situ growth; MXene@Ni/PNF acts as an EM absorption layer while MXene/PNF acts as an EM reflective layer. Finally, (MXene@Ni/PNF)-(MXene/PNF) aerogels are prepared by layer-by-layer freeze-drying based on the layered modular design concept. Experimental characterizations revealed that (MXene@Ni/PNF)-(MXene/PNF) aerogels enable the efficient absorption-reflection-reabsorption of EM waves, effectively eliminating EMI. When the mass ratio of MXene to Ni in MXene@Ni is 1:6 and the mass fraction of MXene in the reflective layer is 80 wt.%, the (MXene@Ni/PNF)-(MXene/PNF) aerogels exhibit excellent EMI shielding performance (71 dB) and a very low reflection coefficient (R = 0.10). Finite element simulations verified that the developed asymmetric structural aerogels achieve high EMI shielding performance with low reflection characteristics. In addition, (MXene@Ni/PNF)-(MXene/PNF) aerogels display excellent infrared camouflage ability.

Design and Synthesis of Multi-compartment Microcapsules via Pickering Emulsion Polymerization for Infrared Stealth and Adaptive Camouflage Applications

High-performance color-changing compounds, recognized as prominent smart materials, dynamically alter their color in response to external environmental stimuli. However, existing compounds exhibit limited responsiveness and color diversity, presenting challenges in the development of textiles responsive to multiple stimuli. This research introduces a novel design for dual-responsive color-changing microcapsules, employing a Pickering emulsion template method. The larger compartment encloses photosensitive dyes, whereas the smaller one contains thermochromic phase-change colorants. Adjusting the density of nanocapsules in the smaller compartment on the microcapsule surface enables a spectrum of colors, including red, yellow, blue, and green, triggered by light and heat. When incorporated into textiles, these microcapsules bestow adaptive color-changing attributes and infrared stealth capabilities onto the fabrics. Additionally, by modulating the color via surface micro/nanostructures, textile surfaces can exhibit hydrophobic and oleophobic properties. Such enhancements extend the textiles' potential applications in areas like anti-counterfeiting and military operations.

Design of a Multifunctional Resin-Based Outdoor Spherical Robot Shell for Ultrahigh Visible to Near-Infrared Transmittance and Mid-Infrared Radiative Cooling

As robots undertake increasingly complex tasks, such as real-time visible image sensing, environmental analysis, and weather monitoring under harsh conditions, design of an appropriate robot shell has become crucial to ensure the reliability of internal electronic components. Several key factors, such as the cooling efficiency, visible transparency, mechanical performance, and weathering resistance of the shell material, are proposed in this research to ensure future robot functionality. In this study, a polymeric double-layered shell for fabrication by stereolithography 3D printing was designed, featuring a porous outer layer and a spherical inner shell. The inner spherical shell provides approximately 90% transmission in the visible to near-infrared wavelength range (450-1050 nm) and ensures the proper functioning of the optical devices, such as cameras, lidar, and solar cells, inside the robot. In addition, the inner shell material displays high emittance in the mid-infrared range (5-20 μm) to facilitate effective radiative cooling and protect the robot control system from thermal damage. The 3D-printed inner shell is exposed to a real environment for three months, and its stable optical and mechanical performance confirms its weather resistance ability. Moreover, the 3D-printed outer robot shell promotes mechanical strength while the robot is moving. The optimal 50% porous outer shell is designed to protect the inner shell from continuous moving impact. Finite element simulations are also used to show that the 50% porosity of the outer shell significantly reduces the strain energy upon impact. Compared with a conventional single-layer design with a strain energy of 130 mJ, the double-layered shell with 50% porosity exhibits a reduced strain energy of 22.09 mJ. This double-layered design, which offers excellent weather resistance, high visible transparency, and effective radiative cooling, is promising for future applications in both land and water robot shells.

Lyotropic "Salty" Tuning for Straightforward Diversification and Anisotropy in Hydrogel Actuators

The specific ion effect (SIE), the control of polymer solubility in aqueous solutions by the added ions, has been a phenomenon known for more than a century. The seemingly simple nature of the ion-polymer-water interactions can lead to complex behaviors, which have also been exploited in many applications in biochemistry, electrochemistry, and energy harvesting. Here, we show an emerging diversification of actuation behaviors in "salty" hydrogel and hydrogel-paper actuators. SIE controls not only the dehydration speeds but also the water diffusion and mechanical properties of the gels, leading to composite actuation behavior. Most reported thermally activated hydrogel actuators suffer from expensive precursors or complex fabrication processes. This work addresses these issues by using a physicochemical effect displayed within an inexpensive gel with common salts. SIE-controlled anisotropic actuation in geometrically different systems provides a demonstration of how such physicochemical effects can lead to higher complexity in basic soft material design and hydrogel soft robotics.

Hybrid Strategies for Enhancing the Multifunctionality of Smart Dynamic Molecular Crystal Materials

Dynamic molecular crystals are an emerging class of smart engineering materials that possess unique ability to convert external energy into mechanical motion. Moreover, they have being considered as strong candidates for dynamic elements in applications such as flexible electronic devices, artificial muscles, sensors, and soft robots. However, the inherent defects of molecular crystals like brittleness, short-life and fatigue, have significantly impeded their practical applications. Inspired by the concept of "the whole is greater than the sum of its parts" in the field of biology, building stimuli-response composites materials can be regarded as one of the ways to break through the current limitations of dynamic molecular crystals. Moreover, the hybrid materials can exhibit new functionalities that cannot be achieved by a single object. In this review, the focus was placed on the analysis and discussion of various hybrid strategies and options, as well as the functionalities of hybrid dynamic molecular crystal materials and the important practical applications of composite materials, with the introduction of photomechanical molecular crystals and flexible molecular crystals as a starting point. Moreover, the efficiency, limitations, and advantages of different hybrid methods were compared and discussed. Furthermore, the promising perspectives of smart dynamic molecular crystal materials were also discussed and the potential directions for future work were suggested.

A Graphene/MXene-Modified Flexible Fabric for Infrared Camouflage, Electrothermal, and Electromagnetic Interference Shielding

Although materials with infrared camouflage capabilities are increasingly being produced, few applications exist in clothing fabrics. Here, graphene/MXene-modified fabric with superior infrared camouflage, Joule heating, and electromagnetic shielding capabilities all in one was prepared by simply scraping a graphene slurry onto alkali-treated cotton fabrics, followed by spraying MXene. The functionality of the modified fabrics after different treatment times was then tested and analyzed. The results indicate that the mid-infrared emissivity of the modified fabric decreases with an increase in the coating times of graphene and MXene. When the graphene/MXene-modified fabrics are prepared at loads of 5 and 1.2 mg/cm2, respectively, the modified fabrics have very low infrared emissivity in the 3-5 and 8-14 μm bands, and the surface temperature can be reduced by 53.1 °C when placed on a heater with a temperature of 100 °C (surface radiation temperature of 95 °C). The modified fabric also demonstrates excellent Joule heating capabilities; at 4 V of power, a temperature of 91.7 °C may be reached in 30 s. In addition, customized materials exhibit strong electromagnetic shielding performance. By simply folding the cloth, the electromagnetic interference shield effect can be increased to 64.3 dB. With their superior infrared camouflage, thermal management, and electromagnetic shielding performance, graphene/MXene-modified fabrics have found extensive use in intelligent wearables and military applications.

A Wide Color Gamut and Noniridescent Zinc-Anode Asymmetric Electrochromic Device for Self-Sustaining Color-Adaptive Bio-Camouflage System

Inspired by camouflage-colored organisms, the development of bio-camouflage systems using electrochromic (EC) technology has gained significant interest. However, existing EC systems struggle with achieving a wide color gamut, noniridescent colors, and self-sustainability. Herein, a self-sustainable color-adaptive bio-camouflage system integrating EC and nanogenerator (NG) technologies, enabling environmental color adaptation, and thermal regulation without an external power source is proposed. The system is based on a zinc-anode EC device (ZECD) with an asymmetric structure, incorporating flexible tungsten oxide and vanadium oxide electrodes. During the EC process, tungsten oxide shifts between blue and transparent, allowing near-infrared thermal modulation, while the vanadium oxide transitions from yellow to transparent. This design enables reversible near-infrared modulation and noniridescent color conversion among black, blue, green, yellow, and transparent. For the self-sustainability of the system, an electromagnetic and triboelectric hybrid NG that collects biomechanical energy is developed. In a typical driven cycle, the integrated system transitions colors and achieves significant near-infrared spectral modulation, demonstrating environmental adaptability and thermal regulation. Experiments on human skin and simulated chameleon color changes further confirm the system's effectiveness. This work highlights the potential of integrating EC and NG technologies to advance color-adaptive camouflage systems, opening new an avenue for bio-camouflage design.

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.

A Soluble ProDOT-Based Polymer and Its Electrochromic Device with Yellow-to-Green Color Switching Towards Camouflage Application

Yellow-to-green electrochromic color switching plays a key role in the intelligent adaptive camouflage under the visible light environment in future military camouflage applications. Here, we designed and synthesized a soluble electrochromic conjugated pDPTD polymer, mainly based on perylo[1,12-bcd]thiophene and the novel ProDOT groups. The pDPTD polymer displayed a yellow-to-green electrochromism with large optical contrast and fast switching times. Based on the pDPTD polymer film, a yellow-to-green electrochromic device was achieved, showing an orange-yellow color at -0.4 V with L*a*b* color coordinates of 88.5, 18.5, and 34.2 and a pale green color at 0.7 V with L*a*b* color coordinates of 85.6, -4.8, and 11.5, together with a large optical contrast of 43.5% and fast switching times of 2.4/3.2 s. These results indicated that the pDPTD polymer could serve as a potential electrochromic material for yellow/green system camouflage applications.

A Proprioceptive Janus Fiber with Controllable Multistage Segments for Bionic Soft Robots

Smart fibers capable of integrating the multifunctionality of actuation and self-sensation into a single proprioceptive device have significant applications in soft robots and biomedicine. Especially, the achievement of self-sensing the movement patterns of different actuating segments in one fiber is still a great challenge. Herein, in this study, a fiber with the controllable Janus architecture is successfully proposed via an artful centrifugation-driven hierarchical gradient self-assembly strategy, which couples two functional components of piezoresistive carbon nanotubes and magnetic NdFeB nanoparticles into the upper and lower layers of this flexible fibrous framework with the porous sponge structure partially, respectively. As predicted, the final product exhibits the as-anticipated bionic proprioceptive behaviors of programmable actuating deformation and highly selective response to bending, stretching, and pressure with high washable stability and mechanical performances. More importantly, assisted by the different three-dimensional printing molds, the superlong Janus fibers with various controllable lengths of the reversed but sequential multistage segments can be fabricated, offering the hybrid magnetic actuation and proprioceptive sensation existing at arbitrary nodes. Therefore, several kinds of soft organism-inspired Janus fiber-derived soft robots with the arbitrarily controlled segmental characters were assembled as the proof-of-concept, which can not only realize a snake or inchworm-inspired successive contracting-stretching deformation and a sperm-inspired self-rotating crawling motion but also self-sense the signals of each segment themselves in real time and then be used to navigate an object to target position in a liquid-filled confined tube. It is believed that this work promotes the further development of proprioceptive soft robots.

Dual-Mode Stretchable Emitter with Programmable Emissivity and Air Permeability

Materials with anisotropic emission characteristics have attracted considerable attention for thermal management. Although many dual-mode emitters have been developed for this purpose in the form of textiles, multilayer films, and photonic structures, multiple functionalities are essential for their versatile applications. Herein, a highly stretchable dual-mode emitter with programmable emissivity and air permeability is presented. The emitter comprises a planar Ge2Sb2Te5 (GST) cavity on one side of a perforated elastomer substrate and an infrared-reflecting metal layer on the other side. With a laser-induced phase transition from amorphous to crystalline GST, the emitter exhibits a large emissivity difference of 0.52 between both sides. The dual-mode emitter remains highly stable without mechanical failure after repeated stretching cycles to a strain of 50%. This air-permeable and stretchable emitter can be attached to any curved surface, including the human body. The GST-side emissivity can be programmed into an arbitrary emissivity pattern using a spatially modulated laser beam, ultimately enabling the printing of mutually independent visible and thermal images in a single emitter. This study provides a promising structure for multispectral optical security as well as thermal management.

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.

Bioinspired Intelligent Ferrofluid: Old Magnetic Material with New Optical Properties

Fine-tuning of microstructures enables the modulation of optical properties at multiple scales from metasurfaces to geometric optics. However, a dynamic system with a significant deformation range and topology transformation remains challenging. Owing to its magnetic controllability, ferrofluid has proven to be fertile ground for a wide range of engineering and technological applications. Here, we demonstrate a series of intelligent optical surfaces based on ferrofluid, through which multiple optical functions inspired by nature can be realized. The tunability is based on the topological transition of the ferrofluid between the flat state and cone array upon magnetic actuation. In the visible band, a tunable visual appearance is realized. In the mid-infrared band, active manipulation of reflection is realized based on the gradient-index (GRIN) effect. This system also features low latency response and straightforward manufacturability, and it may open opportunities for novel technologies such as smart windows, color displays, infrared camouflage, and other infrared-related technologies.

Thin Conducting Films: Preparation Methods, Optical and Electrical Properties, and Emerging Trends, Challenges, and Opportunities

Thin conducting films are distinct from bulk materials and have become prevalent over the past decades as they possess unique physical, electrical, optical, and mechanical characteristics. Comprehending these essential properties for developing novel materials with tailored features for various applications is very important. Research on these conductive thin films provides us insights into the fundamental principles, behavior at different dimensions, interface phenomena, etc. This study comprehensively analyzes the intricacies of numerous commonly used thin conducting films, covering from the fundamentals to their advanced preparation methods. Moreover, the article discusses the impact of different parameters on those thin conducting films' electronic and optical properties. Finally, the recent future trends along with challenges are also highlighted to address the direction the field is heading towards. It is imperative to review the study to gain insight into the future development and advancing materials science, thus extending innovation and addressing vital challenges in diverse technological domains.

Selective-wavelength perfect infrared absorption in Ag@ZnO conical metamaterial structure

We present a new selective Metamaterial Perfect Absorber (MPA) consisting of zinc oxide embedded silver (Ag@ZnO), designed for applications in infrared stealth technology. The numerical simulation included a wide frequency range from 1 to 1000 THz and shows that the design MPA structure presented two absorption peaks at the desired wavelengths of 1.7 µm and 6.5 µm. The absorptivity of both peaks reached approximately 93.1% and 93.5%. The first peak at 1.7 µm decreases the scattering of IR laser beams from the surface of the MPA structure and also lowers the infrared tracks that could direct laser-guided devices to its specific target. On the other hand, the second peak reduces the surface heat wave. The suggested MPA (Ag@ZnO) structure is activated by a plane wave using a full wave vector and a broad frequency domain solution. In the framework of computer simulation technology (CST) Microwave Studio, uses both Finite-Difference-Time-Domain (FDTD) and Finite-Element-Method (FEM) techniques to predict the optical behavior of the proposed MPA structure. Both peaks achieved a high value of absorptivity due to the simultaneous excitation of the electric and magnetic dipole at resonance wavelength.

Dynamic handedness inversion of self-organized helical superstructures enabled by novel thermally stable light-driven chiral hydrazone switches

Chiral hydrazone photoswitch features are its high thermal stability and negative photochromy, making it desirable in the fabrication of thermally stable optical device. However, chiral hydrazones capable of reversibly inversing chirality is scarcely reported. Herein, a series of new chiral hydrazone switches, HI-1, HI-2 and HI-3, were designed and synthesized. Due to the photoinduced configuration changes, the newly synthesized hydrazone photoswitch presents a surprising chirality inversion upon light stimulation. Photoisomerization of light-driven hydrazone switch molecules was investigated by nuclear magnetic resonance (NMR) spectra and Raman spectroscopy. The effect of the intramolecular hydrogen bond on photoresponsiveness was analyzed. By incorporating the photoswitch into a liquid crystal (LC) host, light-driven cholesteric liquid crystals (CLCs) with handedness invertibility, a feasible photonic bandgap tunability, and superior thermal stability were achieved. In addition, according to the optical-driven thermal stability of the hydrazone switches, the fine regulation of light-driven CLC materials with multistage photo stationary states was realized, and the application of CLC materials in erasable and rewritable display panels was also demonstrated.

Cephalopod-Inspired Nanomaterials for Optical and Thermal Regulation: Mechanisms, Applications and Perspectives

The manipulation of interactions between light and matter plays a crucial role in the evolution of organisms and a better life for humans. As a result of natural selection, precise light-regulatory systems of biology have been engineered that provide many powerful and promising bioinspired strategies. As the "king of disguise", cephalopods, which can perfectly control the propagation of light and thus achieve excellent surrounding-matching via their delicate skin structure, have made themselves an exciting source of inspiration for developing optical and thermal regulation nanomaterials. This review presents cutting-edge advancements in cephalopod-inspired optical and thermal regulation nanomaterials, highlighting the key milestones and breakthroughs achieved thus far. We begin with the underlying mechanisms of the adaptive color-changing ability of cephalopods, as well as their special hierarchical skin structure. Then, different types of bioinspired nanomaterials and devices are comprehensively summarized. Furthermore, some advanced and emerging applications of these nanomaterials and devices, including camouflage, thermal management, pixelation, medical health, sensing and wireless communication, are addressed. Finally, some remaining but significant challenges and potential directions for future work are discussed. We anticipate that this comprehensive review will promote the further development of cephalopod-inspired nanomaterials for optical and thermal regulation and trigger ideas for bioinspired design of nanomaterials in multidisciplinary applications.

Self-Thermal Management in Filtered Selenium-Terminated MXene Films for Flexible Safe Batteries

Li-ion batteries with superior interior thermal management are crucial to prevent thermal runaway and ensure safe, long-lasting operation at high temperatures or during rapid discharging and charging. Typically, such thermal management is achieved by focusing on the separator and electrolyte. Here, the study introduces a Se-terminated MXene free-standing electrode with exceptional electrical conductivity and low infrared emissivity, synergistically combining high-rate capacity with reduced heat radiation for safe, large, and fast Li+ storage. This is achieved through a one-step organic Lewis acid-assisted gas-phase reaction and vacuum filtration. The Se-terminated Nb2Se2C outperformed conventional disordered O/OH/F-terminated materials, enhancing Li+-storage capacity by ≈1.5 times in the fifth cycle (221 mAh·g-1 at 1 A·g-1) and improving mid-infrared adsorption with low thermal radiation. These benefits result from its superior electrical conductivity, excellent structural stability, and high permittivity in the infrared region. Calculations further reveal that increased permittivity and conductivity along the z-direction can reduce heat radiation from electrodes. This work highlights the potential of surface groups-terminated layered material-based free-standing flexible electrodes with self-thermal management ability for safe, fast energy storage.

Multispectral smart window: Dynamic light modulation and electromagnetic microwave shielding

A novel multispectral smart window has been proposed, which features dynamic modulation of light transmittance and effective shielding against electromagnetic microwave radiation. This design integrates liquid crystal dynamic scattering and dye doping techniques, enabling the dual regulation of transmittance and scattering within a single-layer smart window. Additionally, the precise control of conductive film thickness ensures the attainment of robust microwave signal shielding. We present a theoretical model for ion movement in the presence of an alternating electric field, along with a novel approach to manipulate negative dielectric constant. The proposed model successfully enables a rapid transition between light transparent, absorbing and haze states, with an optimum drive frequency adjustable to approximately 300 Hz. Furthermore, the resistive design of the conductive layer effectively mitigates microwave radiation within the 2-18 GHz range. These findings offer an innovative perspective for future advancements in environmental construction.

A visible-light regulated luminescent switch based on a spiropyran-derived Pt(II) complex for advanced anti-counterfeiting materials

A dual optical switch regulated by visible light has been developed through an integrated strategy, including luminescent Pt(II) and photochromic spiropyran (SP) as a triplet-sensitizer and photo-regulator building block, respectively. An efficient Förster resonance energy transfer (FRET) process is achieved, along with apparent and emissive color changes under visible light irradiation and temperature stimuli, which was utilized to develop advanced anti-counterfeiting materials.

Recent Advances in Graphene Adaptive Thermal Camouflage Devices

Thermal camouflage is a highly coveted technology aimed at enhancing the survivability of military equipment against infrared (IR) detectors. Recently, two-dimensional (2D) nanomaterials have shown low IR emissivity, widely tunable opto-electronic properties, and compatibility with stealth applications. Among these, graphene and graphene-like materials are the most appealing 2D materials for thermal camouflage applications. In multilayer graphene (MLG), charge density can be effectively tuned through sufficiently intense electric fields or through electrolytic gating. Therefore, MLG's optical properties, like infrared emissivity and absorbance, can be controlled in a wide range by voltage bias. The large emissivity modulation achievable with this material makes it suitable in the design of thermal dynamic camouflage devices. Generally, the emissivity modulation in the multilayered graphene medium is governed by an intercalation process of non-volatile ionic liquids under a voltage bias. The electrically driven reduction of emissivity lowers the apparent temperature of a surface, aligning it with the background temperature to achieve thermal camouflage. This characteristic is shared by other graphene-based materials. In this review, we focus on recent advancements in the thermal camouflage properties of graphene in composite films and aerogel structures. We provide a summary of the current understanding of how thermal camouflage materials work, their present limitations, and future opportunities for development.

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.

High-Power Impulse Magnetron Sputter Deposition of Ag on Self-Assembled Au Nanoparticle Arrays at Low-Temperature Dewetting Conditions

Plasmons have facilitated diverse analytical applications due to the boosting signal detectability by hot spots. In practical applications, it is crucial to fabricate straightforward, large-scale, and reproducible plasmonic substrates. Dewetting treatment, via applying direct thermal annealing of metal films, has been used as a straightforward method in the fabrication of such plasmonic nanostructures. However, tailoring the evolution of the dewetting process of metal films poses considerable experimental complexities, mainly due to nanoscale structure formation. Here, we use grazing-incidence small- and wide-angle X-ray scattering for the in situ investigation of the high-power impulse magnetron sputter deposition of Ag on self-assembled Au nanoparticle arrays at low-temperature dewetting conditions. This approach allows us to examine both the direct formation of binary Au/Ag nanostructure and the consequential impact of the dewetting process on the spatial arrangement of the bimetallic nanoparticles. It is observed that the dewetting at 100 °C is sufficient to favor the establishment of a homogenized structural configuration of bimetallic nanostructures, which is beneficial for localized surface plasmon resonances (LSPRs). The fabricated metal nanostructures show potential application for the surface-enhanced Raman scattering (SERS) detection of rhodamine 6G molecules. As SERS platform, bimetallic nanostructures formed with dewetting conditions turn out to be superior to those without dewetting conditions. The method in this work is envisioned as a facile strategy for the fabrication of plasmonic nanostructures.

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.

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.

Beyond Color Boundaries: Pioneering Developments in Cholesteric Liquid Crystal Photonic Actuators

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.

Preparation of Fibrous Three-Dimensional Porous Materials and Their Research Progress in the Field of Stealth Protection

Intelligent and diversified development of modern detection technology greatly affects the battlefield survivability of military targets, especially infrared, acoustic wave, and radar detection expose targets by capturing their unavoidable infrared radiation, acoustic wave, and electromagnetic wave information, greatly affecting their battlefield survival and penetration capabilities. Therefore, there is an urgent need to develop stealth-protective materials that can suppress infrared radiation, reduce acoustic characteristics, and weaken electromagnetic signals. Fibrous three-dimensional porous materials, with their high porosity, excellent structural adjustability, and superior mechanical properties, possess strong potential for development in the field of stealth protection. This article introduced and reviewed the characteristics and development process of fibrous three-dimensional porous materials at both the micrometer and nanometer scales. Then, the process and characteristics of preparing fibrous three-dimensional porous materials through vacuum forming, gel solidification, freeze-casting, and impregnation stacking methods were analyzed and discussed. Meanwhile, their current application status in infrared, acoustic wave, and radar stealth fields was summarized and their existing problems and development trends in these areas from the perspectives of preparation processes and applicability were analyzed. Finally, several prospects for the current challenges faced by fibrous three-dimensional porous materials were proposed as follows: functionally modifying fibers to enhance their applicability through self-cross-linking; establishing theoretical models for the transmission of thermal energy, acoustic waves, and electromagnetic waves within fibrous porous materials; constructing fibrous porous materials resistant to impact, shear, and fracture to meet the needs of practical applications; developing multifunctional stealth fibrous porous materials to confer full-spectrum broadband stealth capability; and exploring the relationship between material size and mechanical properties as a basis for preparing large-scale samples that meet the application's requirement. This review is very timely and aims to focus researchers' attention on the importance and research progress of fibrous porous materials in the field of stealth protection, so as to solve the problems and challenges of fibrous porous materials in the field of stealth protection and to promote the further innovation of fibrous porous materials in terms of structure and function.

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.

Research Progress of Bioinspired Structural Color in Camouflage

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.

On the isomeric purity of endcap molecules in cholesteric liquid crystal oligomers for near-infrared thermochromic coatings

Structurally coloured responsive materials provide an interesting avenue for the development of autonomous temperature regulating window films. One interesting class of such thermochromic materials is cholesteric liquid crystals. However, cholesteric liquid crystals have rarely been applied in coatings for smart window applications. In this work, we report the synthesis of endcapped cholesteric liquid crystal oligomers and its application as near-infrared thermochromic coatings for windows. Two isomerically pure monoacrylate endcapping molecules and its isomeric mixture are synthesised. The molecules are used to synthesise a variety of endcapped cholesteric liquid crystal oligomers to study the effect of the isomeric purity on the thermochromic properties of the coatings. It is found that while the oligomers are almost identical in composition and phase behaviour, only one isomer produces a clear transparent coating, highlighting the significance of minute isomeric differences. Remarkably, the thermochromic behaviour of the coatings for all oligomers is the same. The best performing oligomer is able to reversibly blueshift by 250 nanometres when heated from room temperature to 100°C, opening the way of cholesteric liquid crystals for use in temperature regulating window films.

Lightweight and drift-free magnetically actuated millirobots via asymmetric laser-induced graphene

Millirobots must have low cost, efficient locomotion, and the ability to track target trajectories precisely if they are to be widely deployed. With current materials and fabrication methods, achieving all of these features in one millirobot remains difficult. We develop a series of graphene-based helical millirobots by introducing asymmetric light pattern distortion to a laser-induced polymer-to-graphene conversion process; this distortion resulted in the spontaneous twisting and peeling off of graphene sheets from the polymer substrate. The lightweight nature of graphene in combine with the laser-induced porous microstructure provides a millirobot scaffold with a low density and high surface hydrophobicity. Magnetically driven nickel-coated graphene-based helical millirobots with rapid locomotion, excellent trajectory tracking, and precise drug delivery ability were fabricated from the scaffold. Importantly, such high-performance millirobots are fabricated at a speed of 77 scaffolds per second, demonstrating their potential in high-throughput and large-scale production. By using drug delivery for gastric cancer treatment as an example, we demonstrate the advantages of the graphene-based helical millirobots in terms of their long-distance locomotion and drug transport in a physiological environment. This study demonstrates the potential of the graphene-based helical millirobots to meet performance, versatility, scalability, and cost-effectiveness requirements simultaneously.

Ultrasensitive Biomimetic Skin with Multimodal and Photoelectric Dual-Signal Sensing

Mimicking biological skin enabling direct, intelligent interaction between users and devices, multimodal sensing with optical/electrical (OE) output signals is urgently required. Owing to this, this work aims to logically design a stretchable OE biomimetic skin (OE skin), which can sensitively sense complex external stimuli of pressure, strain, temperature, and localization. The OE skin consists of elastic thin polymer-stabilized cholesteric liquid crystal films, an ion-conductive hydrogel layer, and an elastic protective membrane formed with thin polydimethylsiloxane. The as-designed OE skin exhibits customizable structural color on demand, good thermochromism, and excellent mechanochromism, with the ability to extend the full visible spectrum, a good linearity of over 0.99, fast response speed of 93 ms, and wide temperature range of 119 °C. In addition, the conduction resistance variation of ion-conductive hydrogel exhibits excellent sensing capabilities under pressure, stretch, and temperature, endowing a good linearity of 0.99998 (stretching from 0 to 150%) and high thermal sensitivity of 0.86% per °C. Such an outstanding OE skin provides design concepts for the development of multifunctional biomimetic skin used in human-machine interaction and can find wide applications in intelligent wearable devices and human-machine interactions.

Perovskite Smart Windows: The Light Manipulator in Energy-Efficient Buildings

Uncontrolled sunlight entering through windows contributes to substantial heating and cooling demands in buildings, which leads to high energy consumption from the buildings. Recently, perovskite smart windows have emerged as innovative energy-saving technologies, offering the potential to adaptively control indoor solar heat gain through their impressive sunlight modulation capabilities. Moreover, harnessing the high-efficiency photovoltaic properties of perovskite materials, these windows have the potential to generate power, thereby realizing more advanced windows with combined light modulation and energy harvesting capabilities. This review summarizes the recent advancements in various chromic perovskite materials for achieving light modulation, focusing on both perovskite structures and underlying switching mechanisms. The discussion also encompasses device engineering strategies for smart windows, including the improvement of their optical and transition performance, durability, combination with electricity generation, and the evaluation of their energy-saving performance in building applications. Furthermore, the challenges and opportunities associated with perovskite smart windows are explicated, aimed at stimulating more academic research and advancing their pragmatic implementation for building energy efficiency and sustainability.

Shape programming of liquid crystal elastomers

Liquid crystal elastomers (LCEs) are shape-morphing materials that demonstrate reversible actuation when exposed to external stimuli, such as light or heat. The actuation's complexity depends heavily on the instilled liquid crystal alignment, programmed into the material using various shape-programming processes. As an unavoidable part of LCE synthesis, these also introduce geometrical and output restrictions that dictate the final applicability. Considering LCE's future implementation in real-life applications, it is reasonable to explore these limiting factors. This review offers a brief overview of current shape-programming methods in relation to the challenges of employing LCEs as soft, shape-memory components in future devices.

Advanced Cooling Textiles: Mechanisms, Applications, and Perspectives

High-temperature environments pose significant risks to human health and safety. The body's natural ability to regulate temperature becomes overwhelmed under extreme heat, leading to heat stroke, dehydration, and even death. Therefore, the development of effective personal thermal-moisture management systems is crucial for maintaining human well-being. In recent years, significant advancements have been witnessed in the field of textile-based cooling systems, which utilize innovative materials and strategies to achieve effective cooling under different environments. This review aims to provide an overview of the current progress in textile-based personal cooling systems, mainly focusing on the classification, mechanisms, and fabrication techniques. Furthermore, the challenges and potential application scenarios are highlighted, providing valuable insights for further advancements and the eventual industrialization of personal cooling textiles.

On-demand engineerable visible spectrum by fine control of electrochemical reactions

Tunability of optical performance is one of the key technologies for adaptive optoelectronic applications, such as camouflage clothing, displays, and infrared shielding. High-precision spectral tunability is of great importance for some special applications with on-demand adaptability but remains challenging. Here we demonstrate a galvanostatic control strategy to achieve this goal, relying on the finding of the quantitative correlation between optical properties and electrochemical reactions within materials. An electrochromic electro-optical efficiency index is established to optically fingerprint and precisely identify electrochemical redox reactions in the electrochromic device. Consequently, the charge-transfer process during galvanostatic electrochemical reaction can be quantitatively regulated, permitting precise control over the final optical performance and on-demand adaptability of electrochromic devices as evidenced by an ultralow deviation of <3.0%. These findings not only provide opportunities for future adaptive optoelectronic applications with strict demand on precise spectral tunability but also will promote in situ quantitative research in a wide range of spectroelectrochemistry, electrochemical energy storage, electrocatalysis, and material chemistry.

Reverse-switching radiative cooling for synchronizing indoor air conditioning

Switchable radiative cooling based on the phase-change material vanadium dioxide (VO2) automatically modulates thermal emission in response to varying ambient temperature. However, it is still challenging to achieve constant indoor temperature control solely using a VO2-based radiative cooling system, especially at low ambient temperatures. Here, we propose a reverse-switching VO2-based radiative cooling system, assisting indoor air conditioning to obtain precise indoor temperature control. Unlike previous VO2-based radiative cooling systems, the reverse VO2-based radiative cooler turns on radiative cooling at low ambient temperatures and turns off radiative cooling at high ambient temperatures, thereby synchronizing its cooling modes with the heating and cooling cycles of the indoor air conditioning during the actual process of precise temperature control. Calculations demonstrate that our proposed VO2-based radiative cooling system significantly reduces the energy consumption by nearly 30 % for heating and cooling by indoor air conditioning while maintaining a constant indoor temperature, even surpassing the performance of an ideal radiative cooler. This work advances the intelligent thermal regulation of radiative cooling in conjunction with the traditional air conditioning technology.

Flexible Ag2Se Thermoelectric Films Enable the Multifunctional Thermal Perception in Electronic Skins

Skin is critical for shaping our interactions with the environment. The electronic skin (E-skin) has emerged as a promising interface for medical devices to replicate the functions of damaged skin. However, exploration of thermal perception, which is crucial for physiological sensing, has been limited. In this work, a multifunctional E-skin based on flexible thermoelectric Ag2Se films is proposed, which utilizes the Seebeck effect to replicate the sensory functions of natural skin. The E-skin can enable capabilities including temperature perception, tactile perception, contactless perception, and material recognition by analyzing the thermal conduction behaviors of various materials. To further validate the capabilities of constructed E-skins, a wearable device with multiple sensory channels was fabricated and tested for gesture recognition. This work highlights the potential for using flexible thermoelectric materials in advanced biomedical applications including health monitoring and smart prosthetics.