Radiative human body cooling by nanoporous polyethylene textile

A Hierarchically Nanofibrous Self-Cleaning Textile for Efficient Personal Thermal Management in Severe Hot and Cold Environments

Climate change has recently caused more and more severe temperatures, inducing a growing demand for personal thermal management at outdoors. However, designing textiles that can achieve personal thermoregulation without energy consumption in severely hot and cold environments remains a huge challenge. Herein, a hierarchically nanofibrous (HNF) textile with improved thermal insulation and radiative thermal management functions is fabricated for efficient personal thermal management in severe temperatures. The textile consists of a radiative cooling layer, an intermediate thermal insulation layer, and a radiative heating layer, wherein the porous lignocellulose aerogel membrane (LCAM) as intermediate layer has low thermal conductivity (0.0366 W·m-1·K-1), ensuring less heat loss in cold weather and blocking external heat in hot weather. The introduction of polydimethylsiloxane (PDMS) increases the thermal emissivity (90.4%) of the radiative cooling layer in the atmospheric window and also endows it with a perfect self-cleaning performance. Solar absorptivity (80.1%) of the radiative heating layer is dramatically increased by adding only 0.05 wt% of carbon nanotubes (CNTs) into polyacrylonitrile. An outdoor test demonstrates that the HNF textile can achieve a temperature drop of 7.2 °C compared with white cotton in a hot environment and can be as high as 12.2 °C warmer than black cotton in a cold environment. In addition, the HNF textile possesses excellent moisture permeability, breathability, and directional perspiration performances, making it promising for personal thermal management in severely hot and cold environments.

A Scalable Microstructure Photonic Coating Fabricated by Roll-to-Roll "Defects" for Daytime Subambient Passive Radiative Cooling

The deep space's coldness (∼4 K) provides a ubiquitous and inexhaustible thermodynamic resource to suppress the cooling energy consumption. However, it is nontrivial to achieve subambient radiative cooling during daytime under strong direct sunlight, which requires rational and delicate photonic design for simultaneous high solar reflectivity (>94%) and thermal emissivity. A great challenge arises when trying to meet such strict photonic microstructure requirements while maintaining manufacturing scalability. Herein, we demonstrate a rapid, low-cost, template-free roll-to-roll method to fabricate spike microstructured photonic nanocomposite coatings with Al2O3 and TiO2 nanoparticles embedded that possess 96.0% of solar reflectivity and 97.0% of thermal emissivity. When facing direct sunlight in the spring of Chicago (average 699 W/m2 solar intensity), the coatings show a radiative cooling power of 39.1 W/m2. Combined with the coatings' superhydrophobic and contamination resistance merits, the potential 14.4% cooling energy-saving capability is numerically demonstrated across the United States.

Scalable Bacterial Cellulose-Based Radiative Cooling Materials with Switchable Transparency for Thermal Management and Enhanced Solar Energy Harvesting

Radiative cooling materials that can dynamically control solar transmittance and emit thermal radiation into cold outer space are critical for smart thermal management and sustainable energy-efficient buildings. This work reports the judicious design and scalable fabrication of biosynthetic bacterial cellulose (BC)-based radiative cooling (Bio-RC) materials with switchable solar transmittance, which are developed by entangling silica microspheres with continuously secreted cellulose nanofibers during in situ cultivation. Theresulting film shows a high solar reflection (95.3%) that can be facilely switched between an opaque state and a transparent state upon wetting. Interestingly, the Bio-RC film exhibits a high mid-infrared emissivity (93.4%) and an average sub-ambient temperature drop of ≈3.7 °C at noon. When integrating with a commercially available semi-transparent solar cell, the switchable solar transmittance of Bio-RC film enables an enhancement of solar power conversion efficiency (opaque state: 0.92%, transparent state: 0.57%, bare solar cell: 0.33%). As a proof-of-concept illustration, an energy-efficient model house with its roof built with Bio-RC-integrated semi-transparent solar cell is demonstrated. This research can shine new light on the design and emerging applications of advanced radiative cooling materials.

A Janus membrane doped with carbon nanotubes for wet-thermal management

In a human skin-fibrous fabric-external environment, fibrous materials, as the "second skin" of the human body, provide comfort against the wet and heat effectively. Fibrous materials protect human health and guarantee work efficiency in various outdoor or inner scenes. Personal wet-thermal management based on fibrous materials can regulate comfort in a facile manner with low or zero energy consumption, which has become a potential development area. However, realizing synergistic management of the wet and heat effectively and conveniently is a challenge in the development and production of fibrous materials. We designed and fabricated a Janus fibrous membrane composed of 3-(trimethoxysilyl)propyl methacrylate (TMSPMA)-modified hydrophobic cotton gauze and electrospun carbon nanotubes (CNTs)-doped cellulose acetate (CA) hydrophilic fibrous membrane. Taking advantage of asymmetric wettability along its thickness direction, the Janus fibrous membrane, acting as a "liquid diode", could transport sweat/moisture from human skin to the external environment unidirectionally, which endowed a dry surface on human skin, avoiding "stickiness", and realizing wet management. Doped CNTs had good photothermal-conversion capacity, so the Janus membrane exhibited excellent heating capacity for passive radiation, so excellent synergistic wet-thermal management was obtained. The Janus membrane could be a candidate for diverse applications of fibrous membranes. Our data provide new ideas for the design and fabrication of fibrous membranes with remarkable wet-thermal management.

Capped MIM metamaterial for ultra-broadband perfect absorbing and its application in radiative cooling

Radiative cooling, which needs no external energy to lower the temperature, has drawn great interest in recent years. As a potential candidate, the design of a metamaterial cooler remains a big challenge due to the complexity of the nanostructure and the low average absorptivity. In this work, a capped metal-insulator-metal metamaterial is proposed to achieve ultra-broadband perfect absorbing. The numerical results show that its average absorptivity is 94% in the 8-13 µm wavelength band under normal incidence, bringing about the excellent selective thermal emissivity in the IR atmospheric transparent window. Together with polarization insensitivity and wide angle independency, the proposed metamaterial can realize a net cooling power as high as 120.7W/m 2 under the circumstance without sunshine. As a proof of concept, it is applied to coat the heat sink of a 3D integrated circuit chip. The result shows that the temperature of the observation point lowers 18.3 K after coating. This work offers the promising application of passive radiative cooling in thermal management for personnel, electronic devices, and many others.

Personal Microenvironment Management by Smart Textiles with Negative Oxygen Ions Releasing and Radiative Cooling Performance

In recent years, significant strides have been made in the development of smart clothing, which combines traditional apparel with advanced technology. As our climate and environment undergo continuous changes, it has become critically important to invent and refine sophisticated textiles that enhance thermal comfort and human health. In this study, we present a "wearable forest-like textile". This textile is based on helical lignocellulose-tourmaline composite fibers, boasting mechanical strength that outperforms that of cellulose-based and natural macrofibers. This wearable microenvironment does more than generate approximately 18625 ions/cm³ of negative oxygen ions; it also effectively purifies particulate matter. Furthermore, our experiments demonstrate that the negative oxygen ion environment can slow fruit decay by neutralizing free radicals, suggesting promising implications for aging retardation. In addition, this wearable microenvironment reflects solar irradiation and selectively transmits human body thermal radiation, enabling effective radiative cooling of approximately 8.2 °C compared with conventional textiles. This sustainable and efficient wearable microenvironment provides a compelling textile choice that can enhance personal heat management and human health.

Micro-structured polyethylene film as an optically selective and self-cleaning layer for enhancing durability of radiative coolers

Passive daytime radiative cooling (PDRC) as a zero-energy cooling technology that reflects most of sunlight and emits infrared thermal radiation to outer space, has attracted much attention. However, most PDRC materials suffer dust accumulation problem during long-term use, seriously detrimental to their cooling performance. Here, we demonstrate a micro-structured polyethylene film fabricated through a scalable hot embossing lithography (named HELPE), enables good superhydrophobic property and therefore excellent self-cleaning performance as a universal protective layer for most PDRC materials. Specifically, the precisely designed three-dimensional periodic micron columns on polyethylene film allow for high water droplet contact angle of 151°, and the intrinsic molecular bindings of polyethylene endow low solar absorption (A = 3.3 %) and high mid-infrared transmission (T = 82.3 %) for negligible optical impacts on underlying PDRC materials. Taking polyvinylidene fluoride (PVDF) radiative cooler as an example, when covered with the HELPE film the net cooling performance maintains unchanged (7.5 °C in daytime and 4.5 °C in nighttime) compared to that without HELPE film. After 12 days continuous outdoor experiment, none of obvious dust accumulation can be observed on the radiative cooler covered with HELPE film. Our work offers a universal pathway for most PDRC materials toward practical applications with minimal maintenance need.

Photonic structures in radiative cooling

Radiative cooling is a passive cooling technology without any energy consumption, compared to conventional cooling technologies that require power sources and dump waste heat into the surroundings. For decades, many radiative cooling studies have been introduced but its applications are mostly restricted to nighttime use only. Recently, the emergence of photonic technologies to achieves daytime radiative cooling overcome the performance limitations. For example, broadband and selective emissions in mid-IR and high reflectance in the solar spectral range have already been demonstrated. This review article discusses the fundamentals of thermodynamic heat transfer that motivates radiative cooling. Several photonic structures such as multilayer, periodical, random; derived from nature, and associated design procedures were thoroughly discussed. Photonic integration with new functionality significantly enhances the efficiency of radiative cooling technologies such as colored, transparent, and switchable radiative cooling applications has been developed. The commercial applications such as reducing cooling loads in vehicles, increasing the power generation of solar cells, generating electricity, saving water, and personal thermal regulation are also summarized. Lastly, perspectives on radiative cooling and emerging issues with potential solution strategies are discussed.

A kirigami-enabled electrochromic wearable variable-emittance device for energy-efficient adaptive personal thermoregulation

For centuries, people have put effort to improve the thermal performance of clothing to adapt to varying temperatures. However, most clothing we wear today only offers a single-mode insulation. The adoption of active thermal management devices, such as resistive heaters, Peltier coolers, and water recirculation, is limited by their excessive energy consumption and form factor for long-term, continuous, and personalized thermal comfort. In this paper, we developed a wearable variable-emittance (WeaVE) device, enabling the tunable radiative heat transfer coefficient to fill the missing gap between thermoregulation energy efficiency and controllability. WeaVE is an electrically driven, kirigami-enabled electrochromic thin-film device that can effectively tune the midinfrared thermal radiation heat loss of the human body. The kirigami design provides stretchability and conformal deformation under various modes and exhibits excellent mechanical stability after 1,000 cycles. The electronic control enables programmable personalized thermoregulation. With less than 5.58 mJ/cm2 energy input per switching, WeaVE provides 4.9°C expansion of the thermal comfort zone, which is equivalent to a continuous power input of 33.9 W/m2. This nonvolatile characteristic substantially decreases the required energy while maintaining the on-demand controllability, thereby providing vast opportunities for the next generation of smart personal thermal managing fabrics and wearable technologies.

Recent Advances in Electrospun Membranes for Radiative Cooling

Radiative cooling is an approach that maximizes the thermal emission through the atmospheric window in order to dissipate heat, while minimizing the absorption of incoming atmospheric radiation, to realize a net cooling effect without consuming energy. Electrospun membranes are made of ultra-thin fibers with high porosity and surface area, which makes them suitable for radiative cooling applications. Many studies have investigated the use of electrospun membranes for radiative cooling, but a comprehensive review that summarizes the research progress in this area is still lacking. In this review, we first summarize the basic principles of radiative cooling and its significance in achieving sustainable cooling. We then introduce the concept of radiative cooling of electrospun membranes and discuss the selection criteria for materials. Furthermore, we examine recent advancements in the structural design of electrospun membranes for improved cooling performance, including optimization of geometric parameters, incorporation of highly reflective nanoparticles, and designing multilayer structure. Additionally, we discuss dual-mode temperature regulation, which aims to adapt to a wider range of temperature conditions. Finally, we provide perspectives for the development of electrospun membranes for efficient radiative cooling. This review will provide a valuable resource for researchers working in the field of radiative cooling, as well as for engineers and designers interested in commercializing and developing new applications for these materials.

Scalable Fabrication of Dual-Function Fabric for Zero-Energy Thermal Environmental Management through Multiband, Synergistic, and Asymmetric Optical Modulations

Solar heating and radiative cooling techniques have been proposed for passive space thermal management to reduce the global energy burden. However, the currently used single-function envelope/coating materials can only achieve static temperature regulation, presenting limited energy savings and poor adaption to dynamic environments. In this study, a sandwich-structured fabric, composed of vertical graphene, graphene glass fiber fabric, and polyacrylonitrile nanofibers is developed, with heating and cooling functions integrated through multiband, synergistic, (solar spectrum and mid-infrared ranges) and asymmetric optical modulations on two sides of the fabric. The dual-function fabric demonstrates high adaption to the dynamic environment and superior performance in a zero-energy-input temperature regulation. Furthermore, it demonstrates ≈15.5 and ≈31.1 MJ m^-2 y^-1 higher annual energy savings compared to those of their cooling-only and heating-only counterparts, corresponding to ≈173.7 MT reduction in the global CO₂ emission. The fabric exhibits high scalability for batch manufacturing with commercially abundant raw materials and facile technologies, providing a favorable guarantee of its mass production and use.

Emerging Materials and Strategies for Passive Daytime Radiative Cooling

In recent decades, the growing demands for energy saving and accompanying heat mitigation concerns, together with the vital goal for carbon neutrality, have drawn human attention to the zero-energy-consumption cooling technique. Recent breakthroughs in passive daytime radiative cooling (PDRC) might be a potent approach to combat the energy crisis and environmental challenges by directly dissipating ambient heat from the Earth to the cold outer space instead of only moving the heat across the Earth's surface. Despite significant progress in cooling mechanisms, materials design, and application exploration, PDRC faces potential functionalization, durability, and commercialization challenges. Herein, emerging materials and rational strategies for PDRC devices are reviewed. First, the fundamental physics and thermodynamic concepts of PDRC are examined, followed by a discussion on several categories of PDRC devices developed to date according to their implementation mechanism and material properties. Emerging strategies for performance enhancement and specific functions of PDRC are discussed in detail. Potential applications and possible directions for designing next-generation high-efficiency PDRC are also discussed. It is hoped that this review will contribute to exciting advances in PDRC and aid its potential applications in various fields.

A Janus Textile Capable of Radiative Subambient Cooling and Warming for Multi-Scenario Personal Thermal Management

Textiles with radiative cooling/warming capabilities provide a green and effective solution to personal thermal comfort in different climate scenarios. However, developing multiple-mode textiles for wearing in changing climates with large temperature variation remains a challenge. Here a Janus textile is reported, comprising a polyethersulfone (PES)-Al₂ O₃ cooling layer optically coupled with a Ti₃ C₂ T_x warming layer, which can realize sub-ambient radiative cooling, solar warming, and active Joule heating. Owing to the intrinsically high refractive index of PES and the rational design of the fiber topology, the nanocomposite PES textile features a record high solar reflectance of 0.97. Accompanied by an infrared (IR) emittance of 0.91 in the atmospheric window, sub-ambient cooling of 0.5-2.5 °C is achieved near noontime in humid summer under ≈1000 W m^-2 solar irradiation in Hong Kong. The simulated skin covered with the textile is ≈10 °C cooler than that with white cotton. The Ti₃ C₂ T_x layer provides a high solar-thermal efficiency of ≈80% and a Joule heating flux of 66 W m^-2 at 2 V and 15 °C due to its excellent spectral selectivity and electrical conductivity. The switchable multiple working modes enable effective and adaptive personal thermal management in changing environments.

Colloidal inorganic nano- and microparticles for passive daytime radiative cooling

Compared to traditional cooling systems, radiative cooling (RC) is a promising cooling strategy in terms of reducing energy consumption enormously and avoiding severe environmental issues. Radiative cooling materials (RCMs) reduce the temperature of objects without using an external energy supply by dissipating thermal energy via infrared (IR) radiation into the cold outer space through the atmospheric window. Therefore, RC has a great potential for various applications, such as energy-saving buildings, vehicles, water harvesting, solar cells, and personal thermal management. Herein, we review the recent progress in the applications of inorganic nanoparticles (NPs) and microparticles (MPs) as RCMs and provide insights for further development of RC technology. Particle-based RCMs have tremendous potential owing to the ease of engineering their optical and physical properties, as well as processibility for facile, inexpensive, and large area deposition. The optical and physical properties of inorganic NPs and MPs can be tuned easily by changing their size, shape, composition, and crystals structures. This feature allows particle-based RCMs to fulfill requirements pertaining to passive daytime radiative cooling (PDRC), which requires high reflectivity in the solar spectrum and high emissivity within the atmospheric window. By adjusting the structures and compositions of colloidal inorganic particles, they can be utilized to design a thermal radiator with a selective emission spectrum at wavelengths of 8-13 μm, which is preferable for PDRC. In addition, colloidal particles can exhibit high reflectivity in the solar spectrum through Mie-scattering, which can be further engineered by modifying the compositions and structures of colloidal particles. Recent advances in PDRC that utilize inorganic NPs and MPs are summarized and discussed together with various materials, structural designs, and optical properties. Subsequently, we discuss the integration of functional NPs to achieve functional RCMs. We describe various approaches to the design of colored RCMs including structural colors, plasmonics, and luminescent wavelength conversion. In addition, we further describe experimental approaches to realize self-adaptive RC by incorporating phase-change materials and to fabricate multifunctional RC devices by using a combination of functional NPs and MPs.

Ultrathin, soft, radiative cooling interfaces for advanced thermal management in skin electronics

Thermal management plays a notable role in electronics, especially for the emerging wearable and skin electronics, as the level of integration, multifunction, and miniaturization of such electronics is determined by thermal management. Here, we report a generic thermal management strategy by using an ultrathin, soft, radiative-cooling interface (USRI), which allows cooling down the temperature in skin electronics through both radiative and nonradiative heat transfer, achieving temperature reduction greater than 56°C. The light and intrinsically flexible nature of the USRI enables its use as a conformable sealing layer and hence can be readily integrated with skin electronics. Demonstrations include passive cooling down of Joule heat for flexible circuits, improving working efficiency for epidermal electronics, and stabling performance outputs for skin-interfaced wireless photoplethysmography sensors. These results offer an alternative pathway toward achieving effective thermal management in advanced skin-interfaced electronics for multifunctionally and wirelessly operated health care monitoring.

Engineering Structural Janus MXene-nanofibrils Aerogels for Season-Adaptive Radiative Thermal Regulation

Aerogels have provided a significant platform for passive radiation-enabled thermal regulation, arousing extensive interest due to their capabilities of radiative cooling or heating. However, there still remains challenge of developing functionally integrated aerogels for sustainable thermal regulation in both hot and cold environment. Here, Janus structured MXene-nanofibrils aerogel (JMNA) is rationally designed via a facile and efficient way. The achieved aerogel presents the characteristic of high porosity (≈98.2%), good mechanical strength (tensile stress of ≈2 MPa, compressive stress of ≈115 kPa), and macroscopic shaping property. Based on the asymmetric structure, the JMNA with switchable functional layers can alternatively enable passive radiative heating and cooling in winter and summer, respectively. As a proof of concept, JMNA can function as a switchable thermal-regulated roof to effectively enable the inner house model to maintain >25 °C in winter and <30 °C in hot summer. This design of Janus structured aerogels with compatible and expandable capabilities is promising to widely benefit the low-energy thermal regulation in changeable climate.

Asymmetrical Emissivity and Wettability in Stitching Treble Weave Metafabric for Synchronous Personal Thermal-Moisture Management

Developing textiles with passive thermal management is an effective strategy to maintain the human body healthy as well as decrease energy consumption. Personal thermal management (PTM) textiles with engineered constituent element and fabric structure have been developed, however the comfortability and robustness of these textiles remains a challenge due to the complexity of passive thermal-moisture management. Here a metafabric with asymmetrical stitching treble weave based on woven structure design and yarn functionalization is developed, in which the thermal radiation regulation and moisture-wicking can be achieved simultaneously throughout the dual-mode metafabric due to its optically regulated property, multi-branched through-porous structure and surface wetting difference. With simply flipping, the metafabric enables high solar reflectivity (87.6%) and IR emissivity (94%) in the cooling mode, and a low IR emissivity of 41.3% in the heating mode. When overheating and sweating, the cooling capacity reaches to ≈9 °C owing to the synergistic effect of radiation and evaporation. Moreover, the tensile strengths of the metafabric are 46.18 MPa (warp direction) and 37.59 MPa (weft direction), respectively. This work provides a facile strategy to fabricate multi-functional integrated metafabrics with much flexibility and thus has great potential for thermal management applications and sustainable energy.

A Shish-Kebab Superstructure Film for Personal Radiative Cooling

Due to global warming and the energy crisis, incorporating passive radiative cooling into personal thermal management has attracted extensive attention. However, developing a wearable textile that reflects incoming sunlight and allows mid-infrared radiation transmission is still a tough challenge. Herein, a shish-kebab superstructure film was produced via a flow-induced crystallization strategy for personal radiative cooling. The resulting film endowed a high infrared transmittance (87%) and improved sunlight reflectivity (83%). A device was developed to simulate the human body skin, and the temperatures of the shish-kebab film were 2.5 and 2.6 °C lower than that of traditional textile in outdoor and indoor tests, respectively. In order to make the shish-kebab film more wearable, a series of modifications were then carried out. This study demonstrates the substantial potential to personal thermal management textiles.

Efficient and Robust Molecular Solar Thermal Fabric for Personal Thermal Management

Molecular solar thermal (MOST) materials, which can efficiently capture solar energy and release it as heat on demand, are promising candidates for future personal thermal management (PTM) applications, preferably in the form of fabrics. However, developing MOST fabrics with high energy-storage capacity and stable working performance remains a significant challenge because of the low energy density of the molecular materials and their leakage from the fabric. Here, an efficient and robust MOST fabric for PTM using azopyrazole-containing microcapsules with a deep-UV-filter shell is reported. The MOST fabric, which can co-harvest solar and thermal energy, achieves efficient photocharging and photo-discharging (>90% photoconversion), a high energy density of 2.5 kJ m^-2 , and long-term storage sustainability at month scale. Moreover, it can undergo multiple cycles of washing, rubbing, and recharging without significant loss of energy-storage capacity. This MOST microcapsule strategy is easily used for the scalable production of a MOST fabric for solar thermal moxibustion. This achievement offers a promising route for the application of wearable MOST materials with high energy-storage performance and robustness in PTM.

A Single Electronic Tattoo for Multisensory Integration

Wearable electronics are garnering growing interest in various emerging fields including intelligent sensors, artificial limbs, and human-machine interfaces. A remaining challenge is to develop multisensory devices that can conformally adhere to the skin even during dynamic-moving environments. Here, a single electronic tattoo (E-tattoo) based on a mixed-dimensional matrix network, which integrates two-dimensional  MXene nanosheets and one-dimensional cellulose nanofibers/Ag nanowires, is presented for multisensory integration. The multidimensional configurations endow the E-tattoo with excellent multifunctional sensing capabilities including temperature, humidity, in-plane strain, proximity, and material identification. In addition, benefiting from the satisfactory rheology of hybrid inks, the E-tattoos are able to be fabricated through multiple facile strategies including direct writing, stamping, screen printing, and three-dimensional printing on various hard/soft substrates. Especially, the E-tattoo with excellent triboelectric properties also can serve as a power source for activating small electronic devices. It is believed that these skin-conformal E-tattoo systems can provide a promising platform for next-generation wearable and epidermal electronics.

Scalable Colored Subambient Radiative Coolers Based on a Polymer-Tamm Photonic Structure

Daytime radiative coolers cool objects below the air temperature without any electricity input, while most of them are limited by a silvery or whitish appearance. Colored daytime radiative coolers (CDRCs) with diverse colors, scalable manufacture, and subambient cooling have not been achieved. We introduce a polymer-Tamm photonic structure to enable a high infrared emittance and an engineered absorbed solar irradiance, governed by the quality factor (Q-factor). We theoretically determine the theoretical thresholds for subambient cooling through yellow, magenta, and cyan CDRCs. We experimentally fabricate and observe a temperature drop of 2.6-8.8 °C on average during the daytime and 4.0-4.4 °C during the nighttime. Furthermore, we demonstrate a scalable-manufactured magenta CDRC with a width of 60 cm and a length of 500 cm by a roll-to-roll deposition technique. This work provides guidelines for large-scale CDRCs and offers unprecedented opportunities for potential applications with energy-saving, aesthetic, and visual comfort demands.

Radiative-Cooling Composites with Enhanced Infrared Emissivity by Structural Infrared Scattering through Indium Tin Oxide Nanoparticles in a Polymer Matrix

Radiative cooling has attracted tremendous interest as it can tackle global warming by saving energy consumption in heating, ventilation, and air conditioning (HVAC) in buildings. Polymer materials play an important role in radiative cooling owing to their high infrared emissivity. Along this line, numerous studies on optically optimized geometries were carried out to enhance the selective wavelength absorption for high infrared emissivity; however, the polymer material itself relatively was not investigated and optimized enough. Herein, we investigate the infrared radiation (IR) absorption coefficient of various polymer types, and introduce a new concept of radiative-cooling composites. By dispersing the IR scattering medium in a polymer matrix, IR can be effectively scattered and attenuated by the polymer matrix. Indium tin oxide was utilized as the IR scattering medium in a cellulose acetate polymer matrix in this report. The window film was made with this composite and showed an effective cooling performance by outdoor thermal evaluation. This composite opens a new venue to endow materials with enhanced radiative-cooling property regardless of the polymer types.

Structural Engineering of Hierarchical Aerogels Hybrid Networks for Efficient Thermal Comfort Management and Versatile Protection

In recent years, growing concerns regarding energy efficiency and heat mitigation, along with the critical goal of carbon neutrality, have drawn human attention to the zero-energy-consumption cooling technique. Passive daytime radiative cooling (PDRC) can be an invaluable tool for combating climate change by dispersing ambient heat directly into outer space instead of just transferring it across the surface. Although significant progress has been made in cooling mechanisms, materials design, and application exploration, PDRC faces challenges regarding functionality, durability, and commercialization. Herein, a silica nanofiber aerogels (SNAs) functionalized poly(vinylidene fluoride-co-hexafluoropropene) (P(VDF-HFP)) membrane (SFP membrane), inspired by constructional engineering is constructed. As-prepared membranes with flexible network structure combined hierarchical structure design and practicability principal. As the host material for thermal comfort management (TCM) and versatile protection, the SFP membrane features a large surface area, porous structure, and a robust skeleton that can render excellent mechanical properties. Importantly, the SFP membrane can keep exceptional solar reflectivity (0.95) and strong mid-infrared emittance (0.98) drop the temperature to 12.5 °C below ambient and 96 W m^-2 cooling power under typical solar intensities over 910 W m^-2 . This work provides a promising avenue for high performance aerogel membranes that can be created for use in a wide variety of applications.

Recent Advances in Nanomaterials Used for Wearable Electronics

In recent decades, thriving Internet of Things (IoT) technology has had a profound impact on people's lifestyles through extensive information interaction between humans and intelligent devices. One promising application of IoT is the continuous, real-time monitoring and analysis of body or environmental information by devices worn on or implanted inside the body. This research area, commonly referred to as wearable electronics or wearables, represents a new and rapidly expanding interdisciplinary field. Wearable electronics are devices with specific electronic functions that must be flexible and stretchable. Various novel materials have been proposed in recent years to meet the technical challenges posed by this field, which exhibit significant potential for use in different wearable applications. This article reviews recent progress in the development of emerging nanomaterial-based wearable electronics, with a specific focus on their flexible substrates, conductors, and transducers. Additionally, we discuss the current state-of-the-art applications of nanomaterial-based wearable electronics and provide an outlook on future research directions in this field.

Performance of a superamphiphobic self-cleaning passive subambient daytime radiative cooling coating on grain and oil storage structures

The thermal performance of a novel exterior coating material for commonly used grain and food-grain oil structures was investigated. Grain structures included a concrete squat silo and a concrete warehouse while the edible oil structure was a concrete sided tank. The exterior coating provided excellent moisture runoff and solar reflectance properties and is best described as a superamphiphobic self-cleaning passive subambient daytime radiative cooling (SSC-PSDRC) coating. The coating exhibited a remarkable subambient daytime cooling effect in various structures in different climatic regions. Compared with the roof surface temperatures of a cool white-coated concrete grain silo and a gray carbon iron-based edible oil storage tank, those of the PSDRC coated top surfaces could be reduced by 37 °C and 33 °C, respectively. The roof surface temperature of a warehouse painted with a cool-white coating-with a solar reflectance of 0.9 and an emissivity of 0.85-and that of a warehouse with the roof installed with aluminised polymer waterproof membranes were 19 °C and 18 °C higher than that of the PSDRC warehouse, respectively. Consequently, the interior temperature of the wheat pile in the PSDRC grain silo was 10 °C lower than that in the control squat silo. With the inner loop flow temperature control system operating, the interior air temperatures of the PSDRC west-facing separate space were 6 °C and 3 °C higher than those of the cool-white coated and control west-facing separate spaces, respectively. Even after the application of PSDRC coating for only a few days, the interior air temperature of the PSDRC oil storage tank was reduced by 38 °C, and the interior temperature of the oil storage tank was reduced by 4 °C. Furthermore, in practical applications, the coating showed impressive superamphiphobic self-cleaning capabilities and super aging resistance. The wide applications of the coating would have far-reaching, global implications for maintaining grain and edible oil products, particularly in the sub-tropical climates.

A Breathable, Passive-Cooling, Non-Inflammatory, and Biodegradable Aerogel Electronic Skin for Wearable Physical-Electrophysiological-Chemical Analysis

Real-time monitoring of human health can be significantly improved by designing novel electronic skin (E-skin) platforms that mimic the characteristics and sensitivity of human skin. A high-quality E-skin platform that can simultaneously monitor multiple physiological and metabolic biomarkers without introducing skin discomfort or irritation is an unmet medical need. Conventional E-skins are either monofunctional or made from elastomeric films that do not include key synergistic features of natural skin, such as multi-sensing, breathability, and thermal management capabilities in a single patch. Herein, a biocompatible and biodegradable E-skin patch based on flexible gelatin methacryloyl aerogel (FGA) for non-invasive and continuous monitoring of multiple biomarkers of interest is engineered and demonstrated. Taking advantage of cryogenic temperature treatment and slow polymerization, FGA is fabricated with a highly interconnected porous structure that displays good flexibility, passive-cooling capabilities, and ultra-lightweight properties that make it comfortable to wear for long periods of time. It also provides numerous permeable capillary channels for thermal-moisture transfer, ensuring its excellent breathability. Therefore, the engineered FGA-based E-skin can simultaneously monitor body temperature, hydration, and biopotentials via electrophysiological sensors and detect glucose, lactate, and alcohol levels via electrochemical sensors. This work offers a previously unexplored materials strategy for next-generation E-skin platforms with superior practicality.

MOF-Integrated Hierarchical Composite Fiber for Efficient Daytime Radiative Cooling and Antibacterial Protective Textiles

Incorporating passive radiative cooling into textiles is an effective way to improve individual personalized thermophysiological comfort for the human body. Based on radiative cooling textile design, rational functionalization further facilitates practical applications, especially for medical protective products with customized requirements. Herein, we present a hierarchical polyurethane/metal-organic framework (MOF) composite nanofiber membrane with an integrated radiative cooling effect and photocatalytic antibacterial property. Fabricated by a scalable electrospinning method, the hierarchical nanofiber membrane shows high solar reflectance of 97% and improved thermal emissivity of 93% attributed to the abundant chemical bonds in ZIF-8 nanoparticles, rendering a temperature drop of ∼7.2 °C under direct sunlight and ∼5.5 °C at night. In addition, the photocatalytic activity of ZIF-8 ensures a 96% bacterial mortality rate for preventing bacterial infection. In practical application, our composite fabric can prevent superheating by 4.4 °C compared with the traditional protective suit under direct sunlight. Along with its anti-infection ability, the composite fabric is desirable for medical protective textiles. The innovative integration of passive radiative cooling design and functional MOFs breaks through the traditional cooling mode and provides huge substantial advantages for smart textiles and personal cooling applications.

Recent Advances in Thermoregulatory Clothing: Materials, Mechanisms, and Perspectives

Personal thermal management (PTM) is a promising approach for maintaining the thermal comfort zone of the human body while minimizing the energy consumption of indoor buildings. Recent studies have reported the development of numerous advanced textiles that enable PTM systems to regulate body temperature and are comfortable to wear. Herein, recent advancements in thermoregulatory clothing for PTM are discussed. These advances in thermoregulatory clothing have focused on enhancing the control of heat dissipation between the skin and the localized environment. We primarily summarize research on advanced clothing that controls the heat dissipation pathways of the human body, such as radiation- and conductance-controlled clothing. Furthermore, adaptive clothing such as dual-mode textiles, which can regulate the microclimate of the human body, as well as responsive textiles that address both thermal performance (warming and/or cooling) and wearability are discussed. Finally, we include a discussion on significant challenges and perspectives in this field, including large-scale production, smart textiles, bioinspired clothing, and AI-assisted clothing. This comprehensive review aims to further the development of sustainably manufactured advanced clothing with superior thermal performance and outstanding wearability for PTM in practical applications.

Phase Change Material Enhanced Radiative Cooler for Temperature-Adaptive Thermal Regulation

Passive radiative cooling (PRC), as an electricity-free and environmentally friendly cooling strategy, is highly desirable in improving the global energy landscape. Despite numerous efforts, most designs for PRC are so devoted to improving the cooling performance in the daytime that they neglect the triggered overcooling at night. Herein, we approached an effective design for temperature-adaptive thermal management through integrating PRC and temperature control of room-temperature phase change material. Compared with conventional radiative coolers, the developed phase change material-enhanced radiative cooler (PCMRC) can adjust its performance according to the temperature of day and night. The PCMRC achieved an average subambient temperature drop of ∼6.3 °C under direct sunlight and an average temperature rise of ∼2.1 °C above ambient temperature at night, as well as a reduced temperature difference between day and night. The temperature-adaptive PCMRC shows great promise for passive radiative cooling regulation, which can further extend the applications of passive radiative cooling.

A Thermoregulatory Flexible Phase Change Nonwoven for All-Season High-Efficiency Wearable Thermal Management

Phase change materials have a key role for wearable thermal management, but suffer from poor water vapor permeability, low enthalpy value and weak shape stability caused by liquid phase leakage and intrinsic rigidity of solid-liquid phase change materials. Herein, we report for the first time a versatile strategy for designed assembly of high-enthalpy flexible phase change nonwovens (GB-PCN) by wet-spinning hybrid graphene-boron nitride (GB) fiber and subsequent impregnating paraffins (e.g., eicosane, octadecane). As a result, our GB-PCN exhibited an unprecedented enthalpy value of 206.0 J g-1, excellent thermal reliability and anti-leakage capacity, superb thermal cycling ability of 97.6% after 1000 cycles, and ultrahigh water vapor permeability (close to the cotton), outperforming the reported PCM films and fibers to date. Notably, the wearable thermal management systems based on GB-PCN for both clothing and face mask were demonstrated, which can maintain the human body at a comfortable temperature range for a significantly long time. Therefore, our results demonstrate huge potential of GB-PCN for human-wearable passive thermal management in real scenarios.

Radiative cooling for passive thermal management towards sustainable carbon neutrality

Photonic structures at the wavelength scale offer innovative energy solutions for a wide range of applications, from high-efficiency photovoltaics to passive cooling, thus reshaping the global energy landscape. Radiative cooling based on structural and material design presents new opportunities for sustainable carbon neutrality as a zero-energy, ecologically friendly cooling strategy. In this review, in addition to introducing the fundamentals of the basic theory of radiative cooling technology, typical radiative cooling materials alongside their cooling effects over recent years are summarized and the current research status of radiative cooling materials is outlined and discussed. Furthermore, technical challenges and potential advancements for radiative cooling are forecast with an outline of future application scenarios and development trends. In the future, radiative cooling is expected to make a significant contribution to global energy saving and emission reduction.

Electrospun Nanofibrous Membranes: A Versatile Medium for Waterproof and Breathable Application

Waterproof and breathable membranes that prevent liquid water penetration, while allowing air and moisture transmission, have attracted significant attention for various applications. Electrospun nanofiber materials with adjustable pore structures, easily tunable wettability, and good pore connectivity, have shown significant potential for constructing waterproof and breathable membranes. Herein, a systematic overview of the recent progress in the design, fabrication, and application of waterproof and breathable nanofibrous membranes is provided. The various strategies for fabricating the membranes mainly including one-step electrospinning and post-treatment of nanofibers are given as a starting point for the discussion. The different design concepts and structural characteristics of each type of waterproof and breathable membrane are comprehensively analyzed. Then, some representative applications of the membranes are highlighted, involving personal protection, desalination, medical dressing, and electronics. Finally, the challenges and future perspectives associated with waterproof and breathable nanofibrous membranes are presented.

Efficient Warming Textile Enhanced by a High-Entropy Spectrally Selective Nanofilm with High Solar Absorption

Solar and radiative warming are smart approaches to maintaining the human body at a metabolically comfortable temperature in both indoor and outdoor scenarios. Nevertheless, existing warming textiles are ineffective in frigid climates because the solar absorption of selective absorbing coating is significantly reduced when coated on rough textile surface. Herein, for the first time, high-entropy nitrides based spectrally selective film (SSF) is introduced on common cotton through a one-step magnetron sputtering method. The well-designed refractive index gradient enables destructive interference effects, offering a roughness-insensitive high solar absorptance (92.8%) and low thermal emittance (39.2%). Impressively, the solar absorptance is 9.1% higher than the reported best-performing selective nanofilm-based textile. As a result, such a textile achieves a record-high photothermal conversion efficiency (82.2% under 0.6 suns, at 0 °C). This textile yields a 3.5 °C drop in the set-point of indoor air-conditioner temperature. Besides, in a winter morning with an air temperature of 7.5 °C, it warms up the human skin by as large as 12 °C under weak sunlight (350 W m^-2 ). More importantly, such a superior radiative warming performance is achieved by engineering the widely used cotton without compromising its breathability and durability, showing great potential for practical applications.

Passive Daytime Radiative Cooling by Thermoplastic Polyurethane Wrapping Films with Controlled Hierarchical Porous Structures

Current research has focused on effective solutions to mitigate global warming and the accelerating greenhouse gas emissions. Compared to most cooling methods requiring energy and resources, passive daytime radiative cooling (PDRC) technology offers excellent energy savings as it requires no energy consumption. However, existing PDRC materials encounter unprecedented problems such as complex structures, low flexibility, and performance degradation after stretching. Thus, this study reports a porous structured thermoplastic polyurethane (TPU) film with bimodal pores to produce high-efficiency PDRC with efficient solar scattering using a simple process. The TPU film exhibited an adequately high solar reflectivity of 0.93 and an emissivity of 0.90 in the atmospheric window to achieve an ambient cooling of 5.6 °C at midday under a solar intensity of 800 W m^-2 . Thus, the highly elastic and flexible TPU film was extremely suitable for application on objects with complex shapes. The radiative cooling performance of 3D-printed models covered with these TPU films demonstrated their superior indoor cooling efficiency compared to commercial white paint (8.76 °C). Thus, the proposed design of high-efficiency PDRC materials is applicable in various urban infrastructural objects such as buildings and vehicles.

Personal Cooling Garments: A Review

Thermal comfort is of critical importance to people during hot weather or harsh working conditions to reduce heat stress. Therefore, personal cooling garments (PCGs) is a promising technology that provides a sustainable solution to provide direct thermal regulation on the human body, while at the same time, effectively reduces energy consumption on whole-building cooling. This paper summarizes the current status of PCGs, and depending on the requirement of electric power supply, we divide the PCGs into two categories with systematic instruction on the cooling materials, working principles, and state-of-the-art research progress. Additionally, the application fields of different cooling strategies are presented. Current problems hindering the improvement of PCGs, and further development recommendations are highlighted, in the hope of fostering and widening the prospect of PCGs.

Air-Conditioned Masks Using Nanofibrous Networks for Daytime Radiative Cooling

Face masks, as effective measures for passive air pollution control, are of fundamental importance, especially with the outbreak of emerging infectious diseases. Most existing masks are dense or thick, resulting in a lack of thermal/humidity comfort level; despite being worn tightly, they show limited PM_0.3/pathogen removal. Here, we use a facile strategy to create air-conditioned masks using heterogeneous nanofibrous networks, based on an electrospinning/netting technique. Manipulation of the phase separation and self-assembly of charged jet/droplets by control of humidity-induced double diffusion and Taylor cone instability allows for the generation of air-conditioned masks consisting of radiative cooling wrinkled nanofibers and 2D nanostructured networks. Our masks show desirable microenvironment with high-efficiency PM_0.3 removal (>99.988%), low air resistance (0.07% of atmospheric pressure), and remarkable radiative cooling capacity (∼2.8 °C temperature and ∼10% humidity drop), making high-performance filtration and temperature/humidity management "always online". This work should make possible the development of high-performance, energy-saving, and scalable fiber textiles for various applications.

Structure Design of Polymer-Based Films for Passive Daytime Radiative Cooling

Passive daytime radiative cooling (PDRC), a cooling method that needs no additional energy, has become increasingly popular in recent years. The combination of disordered media and polymeric photonics will hopefully lead to the large-scale fabrication of high-performance PDRC devices. This work aims to study two typical PDRC structures, the randomly distributed silica particle (RDSP) structure and the porous structure, and systematically investigates the effects of structural parameters (diameter D, volume fraction fv, and thickness t) on the radiative properties of the common plastic materials. Through the assistance of the metal-reflective layer, the daytime cooling power Pnet of the RDSP structures is slightly higher than that of the porous structures. Without the metal-reflective layer, the porous PC films can still achieve good PDRC performance with Pnet of 86 W/m2. Furthermore, the effective thermal conductivity of different structures was evaluated. The single-layer porous structure with optimally designed architecture can achieve both good optical and insulating performance, and it is the structure with the most potential in PDRC applications. The results can provide guidelines for designing high-performance radiative cooling films.

Elastic Fibers/Fabrics for Wearables and Bioelectronics

Wearables and bioelectronics rely on breathable interface devices with bioaffinity, biocompatibility, and smart functionality for interactions between beings and things and the surrounding environment. Elastic fibers/fabrics with mechanical adaptivity to various deformations and complex substrates, are promising to act as fillers, carriers, substrates, dressings, and scaffolds in the construction of biointerfaces for the human body, skins, organs, and plants, realizing functions such as energy exchange, sensing, perception, augmented virtuality, health monitoring, disease diagnosis, and intervention therapy. This review summarizes and highlights the latest breakthroughs of elastic fibers/fabrics for wearables and bioelectronics, aiming to offer insights into elasticity mechanisms, production methods, and electrical components integration strategies with fibers/fabrics, presenting a profile of elastic fibers/fabrics for energy management, sensors, e-skins, thermal management, personal protection, wound healing, biosensing, and drug delivery. The trans-disciplinary application of elastic fibers/fabrics from wearables to biomedicine provides important inspiration for technology transplantation and function integration to adapt different application systems. As a discussion platform, here the main challenges and possible solutions in the field are proposed, hopefully can provide guidance for promoting the development of elastic e-textiles in consideration of the trade-off between mechanical/electrical performance, industrial-scale production, diverse environmental adaptivity, and multiscenario on-spot applications.

Spider-Silk-Inspired Nanocomposite Polymers for Durable Daytime Radiative Cooling

Passive daytime radiative cooling (PDRC) materials, that strongly reflect sunlight and emit thermal radiation to outer space, demonstrate great potential in energy-saving for sustainable development. Particularly, polymer-based PDRC materials, with advantages of easy-processing, low cost, and outstanding cooling performance, have attracted intense attention. However, just like other polymer devices (for example polymer solar cells) working under sunlight, the issue of durability related to mechanical and UV properties needs to be addressed for large-scale practical applications. Here, a spider-silk-inspired design of nanocomposite polymers with potassium titanate (K₂ Ti₆ O₁₃ ) nanofiber dopants is proposed for enhancing the durability without compromising their cooling performance. The formed tough interface of nanofiber/polymer effectively disperses stress, enhancing the mechanical properties of the polymer matrix; while the K₂ Ti₆ O₁₃ can absorb high-energy UV photons and transform them into less harmful heat, thereby improving the UV stabilities. Taking poly(ethylene oxide) radiative cooler as an example for demonstration, its Young's modulus and UV resistance increase by 7 and 12 times, respectively. Consequently, the solar reflectance of nanocomposite poly(ethylene oxide) is maintained as constant in a continuous aging test for 720 h under outdoor sunlight. The work provides a general strategy to simultaneously enhance both the mechanical stability and the UV durability of polymer-based PDRC materials toward large-scale applications.

Rapid Ferroelectric-Photoexcited Bacteria-Killing of Bi4Ti3O12/Ti3C2T x Nanofiber Membranes

In this study, an antibacterial nanofiber membrane [polyvinylidene fluoride/Bi4Ti3O12/Ti3C2T x (PVDF/BTO/Ti3C2T x )] is fabricated using an electrostatic spinning process, in which the self-assembled BTO/Ti3C2T x heterojunction is incorporated into the PVDF matrix. Benefiting from the internal electric field induced by the spontaneously ferroelectric polarization of BTO, the photoexcited electrons and holes are driven to move in the opposite direction inside BTO, and the electrons are transferred to Ti3C2T x across the Schottky interface. Thus, directed charge separation and transfer are realized through the cooperation of the two components. The recombination of electron-hole pairs is maximumly inhibited, which notably improves the yield of reactive oxygen species by enhancing photocatalytic activity. Furthermore, the nanofiber membrane with an optimal doping ratio exhibits outstanding visible light absorption and photothermal conversion performance. Ultimately, photothermal effect and ferroelectric polarization enhanced photocatalysis endow the nanofiber membrane with the ability to kill 99.61% ± 0.28% Staphylococcus aureus and 99.71% ± 0.16% Escherichia coli under 20 min of light irradiation. This study brings new insights into the design of intelligent antibacterial textiles through a ferroelectric polarization strategy.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s42765-022-00234-8.

Smart Humidly Adaptive Yarns and Textiles from Twisted and Coiled Viscose Fiber Artificial Muscles

The self-adaptive nature of smart textiles to the ambient environment has made them an indispensable part of emerging wearable technologies. However, current advances generally suffer from complex material preparation, uncomfortable fitting feeling, possible toxicity, and high cost in fabrication, which hinder the real-world application of smart materials in textiles. Herein, humidity-response torsional and tensile yarn actuators from twisted and coiled structures are developed using commercially available, cost-effective, and biodegradable viscose fibers based on yarn-spinning and weaving technologies. The twisted yarn shows a reversible torsional stroke of 1400° cm^-1 in 5 s when stimulated by water fog with a spraying speed of 0.05 g s^-1; the coiled yarn exhibits a peak tensile stroke of 900% upon enhancing the relative humidity. Further, textile manufacturing allows for the scalable fabrication to create fabric artificial muscles with high-dimensional actuation deformations and human-touch comfort, which can boost the potential applications of the humidly adaptive yarns in smart textile and advanced textile materials.

Superhydrophobic Porous Coating of Polymer Composite for Scalable and Durable Daytime Radiative Cooling

Passive daytime radiative cooling (PDRC) technology provides an eco-friendly cooling strategy by reflecting sunlight reaching the surface and radiating heat underneath to the outer space through the atmospheric transparency window. However, PDRC materials face challenges in cooling performance degradation caused by outdoor contamination and requirements of easy fabrication approaches for scale-up and high cooling efficiency. Herein, a polymer composite coating of polystyrene, polydimethylsiloxane and poly(ethyl cyanoacrylate) (PS/PDMS/PECA) with superhydrophobicity and radiative cooling performance was fabricated and demonstrated to have sustained radiative cooling capability, utilizing the superhydrophobic self-cleaning property to maintain the optical properties of the coating surface. The prepared coating is hierarchically porous which exhibits an average solar reflectance of 96% with an average emissivity of 95% and superhydrophobicity with a contact angle of 160°. The coating realized a subambient radiative cooling of 12.9 °C in sealed air and 7.5 °C in open air. The self-cleaning property of the PS/PDMS/PECA coating helped sustain the cooling capacity for long-term outdoor applications. Moreover, the coating exhibited chemical resistance, UV resistance, and mechanical durability, which has promising applications in wider fields.

Ultralight and Superelastic Gd2O3/Bi2O3 Nanofibrous Aerogels with Nacre-Mimetic Brick-Mortar Structure for Superior X-ray Shielding

The widespread use of X-rays has prompted a surge in demand for effective and wearable shielding materials. However, the Pb-containing materials currently used to shield X-rays are commonly bulky, hard, and biotoxic, severely limiting their applications in wearable scenarios. Inspired by the nacre, we report on ultralight, superelastic, and nontoxic X-ray shielding nanofibrous aerogels with microarch-engineered brick/mortar structure by combining polyurethane/Bi₂O₃ nanofibers (brick) and Gd₂O₃ nanosheets (mortar). The synergistic attenuation effect toward X-rays from the reflection of microarches and absorption of Bi/Gd elements significantly enhances the shielding efficiency of aerogels, and microarches/robust nanofibrous networks endow the materials with superelasticity. The resultant materials exhibit integrated properties of superior X-ray shielding efficiency (91-100%), ultralow density (52 mg cm^-3), large stretchability of 800% reversible elongation, and high water vapor permeability (8.8 kg m^-2 day^-1). The fabrication of such novel aerogels paves the way for developing next-generation effective and wearable X-ray shielding materials.

Microgels based on 0D-3D carbon materials: Synthetic techniques, properties, applications, and challenges

Microgels are three-dimensional (3D) colloidal hydrogel particles with outstanding features such as biocompatibility, good mechanical properties, tunable sizes from submicrometer to tens of nanometers, and large surface areas. Because of these unique qualities, microgels have been widely used in various applications. Carbon-based materials (CMs) with various dimensions (0-3D) have recently been investigated as promising candidates for the design and fabrication of microgels because of their large surface area, excellent conductivity, unique chemical stability, and low cost. Here, we provide a critical review of the specific characteristics of CMs that are being incorporated into microgels, as well as the state-of-the art applications of CM-microgels in pollutant adsorption and photodegradation, H₂ evoluation, CO₂ capture, soil conditioners, water retention, drug delivery, cell encapsulation, and tissue engineering. Advanced preparation techniques for CM-microgel systems are also summarized and discussed. Finally, challenges related to the low colloidal stability of CM-microgels and development strategies are examined. This review shows that CM-microgels have the potential to be widely used in various practical applications.

An Integrated 3D Hydrophilicity/Hydrophobicity Design for Artificial Sweating Skin (i-TRANS) Mimicking Human Body Perspiration

Artificial skins reproducing properties of human skin are emerging and significant for study in various areas, such as robotics, medicine, and textiles. Perspiration, as one of the most imperative thermoregulation functions of human skin, is gaining increasing attention, but how to realize ideal artificial skin for perspiration simulation remains challenging. Here, an integrated 3D hydrophilicity/hydrophobicity design is proposed for artificial sweating skin (i-TRANS). Based on normal fibrous wicking materials, the selective surface modification with gradient of poly(dimethylsiloxane) (PDMS) creates hydrophilicity/hydrophobicity contrast in both lateral and vertical directions. With the additional help of bottom hydrophilic Nylon 6 nanofibers, the constructed i-TRANS is able to transport "sweat" directionally without trapping undesired excess water and attain uniform "secretion" of sweat droplets on the top surface, decently mimicking human skin perspiration situation. This fairly comparable simulation not only presents new insights for replicating skin properties, but also provides proper in vitro testing platforms for perspiration-relevant research, greatly avoiding unwanted interference from the "skin" layer. In addition, the facile, fast, and cost-effective fabrication approach and versatile usage of i-TRANS can further facilitate its application.