Scalable Flexible Hybrid Membranes with Photonic Structures for Daytime Radiative Cooling

Passive radiative cooling technology can cool down an object by reflecting solar light and radiating heat simultaneously. However, photonic radiators generally require stringent and nanoscale‐precision fabrication, which greatly restricts mass production and renders them less attractive for large‐area applications. A simple, inexpensive, and scalable electrospinning method is demonstrated for fabricating a high‐performance flexible hybrid membrane radiator (FHMR) that consists of polyvinylidene fluoride/tetraethyl orthosilicate fibers with numerous nanopores inside and SiO₂ microspheres randomly distributed across its surface. Even without silver back‐coating, a 300 µm thick FHMR has an average infrared emissivity >0.96 and reflects ≈97% of solar irradiance. Moreover, it exhibits great flexibility and superior strength. The daytime cooling performance this device is experimentally demonstrated with an average radiative cooling power of 61 W m^?2 and a temperature decrease up to 6 °C under a peak solar intensity of 1000 W m^?2. This performance is comparable to those of state‐of‐the‐art devices.     

Scalable Aqueous Processing-Based Passive Daytime Radiative Cooling Coatings

Passive daytime radiative cooling (PDRC) can realize electricity-free cooling by reflecting sunlight and emitting heat to the cold space. Current PDRC designs often involve costly vacuum processing or a large quantity of harmful organic solvents. Aqueous and paint-like processing is cost-effective and environmentally benign, thereby highly attractive for green manufacturing of PDRC coatings. However, common polymers explored in PDRC are difficult to disperse in water, let alone forming porous structures for efficient cooling. Here, a simple “bottom-up” ball milling approach to create uniform microassembly of poly(vinylidene fluoride-co-hexafluoropropene) nanoparticles is reported. The micro- and nanopores among secondary particles and primary particles substantially enhance light scattering and results in excellent PDRC performance. A high solar reflectance of 0.94 and high emittance of 0.97 are achieved, making the coating 3.3 and 1.7 °C cooler than commercial white paints and the ambient temperature, under a high solar flux of ≈1100 W m⁻². More importantly, the volatile organic compound content in the aqueous paint is only 71 g L⁻¹. This satisfies the general regulatory requirements, which are critical to sustainability and practical applications.     

光子晶体光纤的原理、应用和制作

光子晶体光纤是一种新型光纤,它与传统光纤相比在结构和性能上有显著的差别和优势。简要分析了光子晶体光纤的原理,并介绍了其特性、应用、分析和制作方法。     

Reconfigurable and Renewable Nano-Micro-Structured Plastics for Radiative Cooling

Passive radiative technology enables sustainable cooling by synchronously emitting heat and reflecting solar light without any energy consumption. However, the consumption of non-recyclable and non-renewable radiative materials in large quantities may eventually cause resource waste and environmental issues. Herein, reconfigurable and renewable nano-micro-structured plastics for future eco-friendly and large-scale radiative cooling applications are developed. The plastics are facilely prepared from a locally confined polymerization method, which not only enables the customization of nano/micro-structures for thermal emission and sunlight reflection but also provides physically cross-linked networks for damage repairing, shape reconfiguration, and recyclable usage. Compared with traditional plastics applied on electronic devices, the nano-micro-structured plastic achieves much higher cooling efficiency with a temperature drop of 8.6 °C on electronic circuits and 7.5 °C cooling improvements under sunlight. With the excellent cooling performance and the recycling potential, the nano-micro-structured plastics open an environmentally sustainable pathway to address the thermal issues encountered by electronic devices and challenges of global warming.     

Visibly Clear Radiative Cooling Metamaterials for Enhanced Thermal Management in Solar Cells and Windows

The study of transparent daytime radiative cooling with no additional energy consumption is a promising area of research. Its applications include solar cells and building and automobile windows that are prone to heating issues. Ubiquitous applications necessitate the development of metamaterials with high mechanical flexibility in a scalable manner while overcoming translucence. In this study, visibly clear and flexible radiative cooling metamaterials have been developed using a newly designed optical modulator filled into randomly distributed silica aerogel microparticles in a silicone elastomer. The optical modulator effectively suppresses visible light scattering, thus enabling higher loading of silica aerogel microparticles while securing visible clarity. The significant suppression of the rise in temperature by the metamaterial is verified using both indoor and outdoor experiments. The visibly clear metamaterials deployed in solar cells and windows can effectively suppress the rise in temperature under solar irradiation, thereby mitigating the performance degradation of solar cells by heating issues and suppressing the rise in temperature of indoor air.     

Eco-Friendly Transparent Silk Fibroin Radiative Cooling Film for Thermal Management of Optoelectronics

Although transparent radiative cooling is a passive cooling strategy with practical applications and aesthetic appeal, complex manufacturing processes and the use of environmentally unfriendly thermal emitters remain latent problems. Herein, eco-friendly transparent silk radiative cooling (TSRC) films are developed, regenerated from natural silkworm cocoons, for zero-energy-consumption thermal management of optoelectronic devices. These TSRC films can dissipate heat radiatively through molecular vibrations of the protein backbone and side chains, while retaining the function and appearance of the associated devices, due to their high visible transparency. Theoretical and experimental investigations revealed that the thermal emission increases rapidly upon increasing the film thickness, but slowly thereafter achieves saturation; nevertheless, the intrinsic solar absorption of silk in the ultraviolet and near-infrared regions also grows linearly, unavoidably weakening the cooling effect. After spectroscopic optimization, the maximum cooling power during the daytime and nighttime is improved to 77.6 and 101.7 W m⁻², respectively. Gratifyingly, the films have a remarkable effect on the cooling performance of electronic devices under sunlight. For example, the TSRC film provides a temperature drop of 5.1 °C for a smartphone during multitasking and charging, and 14 °C for a silicon solar panel with an improvement in the photoelectronic conversion efficiency (≈7%).     

Fabrication of Bioinspired Hierarchical Functional Structures by Using Honeycomb Films as Templates

A facile approach to the fabrication of bioinspired hierarchical functional structures by using honeycomb films with controllable micropores as templates is described here. Taking advantage of the breath figure method, honeycomb films with manipulable micropores can be conveniently fabricated by modulating the experimental conditions such as duration of the moist gas flow, temperature, and stretching of the film, which further serve as templates to induce the assembly of subsequently introduced silica nanoparticles for the construction of hierarchical functional structures in a controlled fashion. The resultant hierarchical functional structures not only present a viewing angle independent property, but also exhibit improved hydrophobicity and unique wetting behaviors depending on the morphologies of their building units. It is believed that the work will provide plenty of inspiration for the fabrication of novel high‐performance optical devices for display, as well as functionalized surfaces for waterproof and self‐cleaning.     

Si基光子晶体的制备与器件应用

光子晶体是近十年来迅速发展起来的一种新型人工结构的功能材料。本文简要介绍了Si基光子晶体的主要特点;着重介绍了Si基光子晶体的几种主要制备方法,如精细干式蚀刻法、胶质晶体模板法、宏观多孔Si的电化学腐蚀、多光子聚合法和核壳结构纳米晶粒镶嵌法等;概要介绍了Si基光子晶体在Si基发光器件和Si基光波导器件中的应用。对目前存在的问题进行了讨论,并展望了它的未来发展趋势。     

Advanced Thermoelectric Materials for Flexible Cooling Application

Flexible cooling devices, which aim to fulfill the essential requirement of complex working environments and enable local heat dissipation, have become the cutting-edge area of refrigeration technology. Thermoelectric (TE) material represents a promising candidate for various flexible cooling applications, including wearable personal thermoregulation devices. With the increasing interest in the Peltier effect of conductive polymers and inorganic films on flexible substrates, flexible cooling devices have undergone rapid development. Herein, the fundamental mechanisms, basic parameters, and temperature measurement techniques for evaluating the cooling performance are summarized. Moreover, recent progress on TE materials, such as flexible inorganic and organic materials for Peltier cooling studies, is reviewed. More importantly, insights are provided into the key strategies for high-performance Peltier devices. The final part details the existing challenges and perspectives on flexible TE cooling to inspire additional research interests toward the advancement of refrigeration technology.     

Vapor Exchange Induced Particles-Based Sponge for Scalable and Efficient Daytime Radiative Cooling

Passive daytime radiative cooling technology (DRCT) has recently gained significant attention for its ability to achieve sub-ambient temperature without energy consumption, making it an attractive option for space cooling. The cooling performance can be further improved if radiative cooling materials also exhibit high thermal insulation performance. However, synthesizing radiative cooling materials that possess low thermal conductivity while maintaining mechanical durability remains a challenge. Here, a vapor exchange method is developed to prepare particles-based poly(vinylidene fluoride-co-hexafluoropropylene) sponge materials for scalable and efficient daytime radiative cooling. By tailoring the particle diameter distribution, high solar reflection (94.5%), high infrared emissivity (0.956), and low thermal conductivity (0.048 W m⁻¹ K⁻¹) are achieved, resulting in a sub-ambient cooling of 9.8 °C under direct solar irradiation. Additionally, the sponge material exhibits good mechanical durability, sustaining deformation with a strain up to 40%, making it adaptable to diverse scenarios. A radiative cooling material with mechanical durability and thermal insulation can thus pave the way for large-scale applications of DRCT.     

在柔性衬底上制备透明导电薄膜ZnO:Zr(英文)

采用射频磁控溅射法在室温柔性衬底PET上制备了掺锆氧化锌(ZZO)透明导电薄膜.利用不同方法提高了ZZO薄膜的电阻率而未使其可见光透过率降低.X射线衍射(XRD)和扫描电子显微镜(SEM)表明,ZZO薄膜为六角纤锌矿结构的多晶薄膜.在有机衬底和玻璃衬底上制备ZZO薄膜的择优取向不同,前者为(100)晶面,而后者为(002)晶面.在有ZnO缓冲层的PET衬底上制备的ZZO薄膜电阻率比直接生长在玻璃衬底样品上的小.通过优化参数,在PET衬底上制备出了最小电阻率为1.7×10-3Ω·cm、可见光透过率超过93%的ZZO薄膜.实验表明,镀膜之前在柔性衬底上沉积ZnO缓冲层能有效地提高ZZO薄膜的质量.     

Mechanically Reconfigurable Organic Photonic Integrated Circuits Made from Two Electronically Different Flexible Microcrystals

Fabrication of microscale organic photonic integrated circuits (μ-OPIC) from two electronically different flexible crystals via a mechanophotonics approach is demonstrated here. The experiments focus on the mechanical micromanipulation of orange-emitting (E)-1-(4-(dimethylamino)-phenyl)iminomethyl-2-hydroxyl-naphthalene (DPIN) and green-emitting (E)-1-(4-bromo)iminomethyl-2-hydroxyl-naphthalene (BPIN) crystals with atomic force cantilever tip. The flexibility of these crystals originate from molecular H-bonding, C H∙∙∙π, and π···π stacking interactions. These mechanically compliant crystals form exceedingly bent and photonically relevant reconfigurable geometries during micromanipulation, including three μ-OPICs. Remarkably, these μ-OPICs operate through passive-, active-waveguiding and energy transfer mechanisms. Depending upon the crystal's electronic nature (either BPIN or DPIN) receiving the optical signal input, the circuit executes mechanism-selective and direction-specific optical outputs. The presented proof-of-principle concepts can be used to fabricate complex photonic circuits with diverse, flexible crystals performing multiple optical functions.     

Bio‐Inspired Photonic Materials: Prototypes and Structural Effect Designs for Applications in Solar Energy Manipulation

Natural creatures have evolved elaborate photonic nanostructures on multiple scales and dimensions in a hierarchical, organized way to realize controllable absorption, reflection, or transmitting the desired wavelength of the solar spectrum. A bio‐inspired strategy is a powerful and promising way for solar energy manipulation. This feature article presents the state‐of‐the‐art progress on bio‐inspired photonic materials on this particular application. The article first briefly recalls the physical origins of natural photonic effects and catalogues the typical natural photonic prototypes including light harvesting, broadband reflection, selective reflection, and UV/IR response. Next, typical applications are categorized into two primary areas: solar energy utilization and reflection. Recent advances including solar‐to‐electricity, solar‐to‐fuels, solar‐thermal (e.g., photothermal converters, infrared detectors, thermoelectric materials, smart windows, and solar steam generation) are highlighted in the first part. Meanwhile, solar energy reflection involving infrared stealth, radiative cooling, and micromirrors are also addressed. In particular, this article focuses on bioinspired design principles, structural effects on functions, and future trends. Finally, the main challenges and prospects for the next generation of bioinspired photonic materials are discussed, including new design concepts, emerging ideas, and possible strategies.     

Delamination and Wrinkling of Flexible Conductive Polymer Thin Films

Polymer based conductive and transparent thin films are an important class of functional materials at the heart of flexible organic electronic devices. These flexible films are prone to degradation and to mechanical instability leading to the formation of blisters, wrinkles, and cracks. This is detrimental to their use especially in the case of multilayer devices. Here, it is shown that a simple water or solvent drop deposited on such films gives rise to a buckling instability and the formation of several folds due to the tendency of these films to swell in contact with the solvent. A phase diagram of the instability portraying its domain of existence, and thus the means to inhibit it, is proposed. By depositing drops on such films and observing the instability, material parameters such as the elastic modulus of the thin films or their energy of adhesion to the substrate can be estimated reliably. Further, the instability can be harnessed to pattern surfaces at low cost giving rise to percolated and more conductive pathways in the conductive polymer films under scrutiny.     

辐射冷却材料的研究进展及应用

辐射冷却是近来日益得到关注的被动冷却形式,它以外太空为冷源,无需额外消耗能量,在建筑冷却、太阳能电池降温、舒适衣物与可穿戴设备等诸多方面都有着良好的应用前景.本文对辐射冷却的发展历史与冷却原理做了简单回顾,对辐射冷却材料的种类和优缺点进行了系统介绍,并对辐射冷却材料的设计、制备、表征方法进行归纳总结,最后对相关应用领域...     

Organic Field Effect Transistor-Based Photonic Synapses: Materials,Devices, and Applications

Photonic artificial synapses-based neuromorphic computing systems have been regarded as promising candidates for replacing von Neumann-based computing systems due to the high bandwidth, ultrafast signal transmission, low energy consumption, and wireless communication. Although significant progress has been made in developing varied device structures for synaptic emulation, organic field-effect transistors (OFETs) hold the compelling advantages of facile preparation, liable integration, and versatile structures. As a powerful and effective platform for photonic synapses, OFETs can fulfill not only the simulation of simple synaptic functions, but also complex photoelectric dual modulation and simulation of the visual system. Herein, an overview of OFET-based photonic synapses, including functional materials, device configurations, and innovative applications is provided. Meanwhile, rules for selecting materials, mechanism of photoelectric conversion, and fabrication techniques of devices are also highlighted. Finally, challenges and opportunities are all discussed, providing solid guidance for multilevel memory, multi-functional tandem artificial neural system, and artificial intelligence.     

PDCLC膜光电性能的研究以及柔性液晶盒的制备

用紫外光诱导相分离方法制备了聚合物分散胆甾相液晶（PDCLC）薄膜,研究了固化光强对薄膜形态以及光电性能的影响,同时探讨了不同制备条件下PDCLC膜的相形态变化与光电性能之间的关系。研究表明：固化光强较低时相分离较完全,产生的液晶微滴尺寸较大,相应的光电性能包括反射率、对比度以及响应时间有所改善。采用上述探讨的优化条件,成功地制备了尺寸为7cm2的反射式柔性双稳态液晶盒。     

PS/TiO_2复合材料的蛋白石结构光子晶体制备及表征

以乳液聚合得到的单分散性聚苯乙烯(PS)微球为种子,利用原位溶胶凝胶技术在微球的表面上吸附上二氧化钛(TiO2)小颗粒,从而得到PS/TiO2复合微球的乳液,利用乳液的自组装得到了PS/TiO2复合材料的蛋白石结构光子晶体。比较了PS蛋白石结构光子晶体和PS/TiO2复合材料蛋白石结构光子晶体的透射谱,得出复合材料的光子晶体带隙特征比PS光子晶体的带隙特征强。     

A Lyotropic Liquid‐Crystal‐Based Assembly Avenue toward Highly Oriented Vanadium Pentoxide/Graphene Films for Flexible Energy Storage

A novel lyotropic liquid‐crystal (LC) based assembly strategy is developed for the first time, to fabricate composite films of vanadium pentoxide (V₂O₅) nanobelts and graphene oxide (GO) sheets, with highly oriented layered structures. It is found that similar lamellar LC phases can be simply established by V₂O₅ nanobelts alone or by a mixture of V₂O₅ nanobelts and GO nanosheets in their aqueous dispersions. More importantly, the LC phases can be retained with any proportion of V₂O₅ nanobelts and GO, which allows facile optimization of the ratio of each component in the resulting films. Named VrGO, composite films manifest high electrical conductivity, good mechanical stability, and excellent flexibility, which allow them to be utilized as high performance electrodes in flexible energy storage devices. As demonstrated in this work, the VrGO films containing 67 wt% V₂O₅ exhibit excellent capacitance of 166 F g^?1 at 10 A g^?1; superior to those of the previously reported composites of V₂O₅ and nanocarbon. Moreover, the VrGO film in flexible lithium ion batteries delivers a high capacity of 215 mAh g^?1 at 0.1 A g^?1; comparable to the best V₂O₅ based cathode materials.     

3D Conformal Printing and Photonic Sintering of High‐Performance Flexible Thermoelectric Films Using 2D Nanoplates

Flexible thermoelectric (TE) devices hold great promise for energy harvesting and cooling applications, with increasing significance to serve as perpetual power sources for flexible electronics and wearable devices. Despite unique and superior TE properties widely reported in nanocrystals, transforming these nanocrystals into flexible and functional forms remains a major challenge. Herein, demonstrated is a transformative 3D conformal aerosol jet printing and rapid photonic sintering process to print and sinter solution‐processed Bi₂Te_2.7Se_0.3 nanoplate inks onto virtually any flexible substrates. Within seconds of photonic sintering, the electrical conductivity of the printed film is dramatically improved from nonconductive to 2.7 × 10⁴ S m^?1. The films demonstrate a room temperature power factor of 730 µW m^?1 K^?2, which is among the highest values reported in flexible TE films. Additionally, the film shows negligible performance changes after 500 bending cycles. The highly scalable and low‐cost fabrication process paves the way for large‐scale manufacturing of flexible devices using a variety of high‐performing nanoparticle inks.