A Zero-Energy, Zero-Emission Air Conditioning Fabric

Cellulose binary coatings with spherical envelope structure via structure rearrangement in ball milling for integrated radiative cooling-electricity generation

Passive daytime radiative cooling is a zero-energy consumption cooling technology, which can dissipate heat to outer space via infrared radiation. Recently, coupling radiative cooling technology and thermoelectric devices to generate electricity has attracted much attention. However, existing radiative cooling integrated thermoelectric devices still suffer from low-temperature gradient and output voltage. Here, based on the Mie scattering and internal reflection enhancing principle, an impact-inducing geometry reconstruction approach was proposed to fabricate hierarchical nanostructured cellulosic coatings with good daytime cooling performance to achieve stable electricity generation function, which can be realized by using a scalable and facile wet ball milling technology. Guided by the theoretical simulations of the finite difference time domain method (FDTD), the cellulose and TiO2 nanoparticles can assemble into spherical envelope structured coatings drying by the shear, impact, and friction interaction in the ball milling process, dramatically enhancing the Mie scattering and internal reflection of coatings. The cellulosic coatings exhibit sunlight reflectivity of 0.962 and infrared emissivity of 0.94, resulting in a daytime radiative cooling efficiency of 5.9 °C under direct sunlight. Energy Plus stimulation demonstrated 35 % cooling energy and 468.9 kWh of cooling energy can be saved annually in China. Meanwhile, this cellulosic coating-based thermoelectric device can deliver a high voltage output of 150 mV under 1 Sun due to the strong bonding and high-temperature gradient formation (30 °C), which is higher than previous reports. This study will facilitate the development of sustainable power generation device for the goal of green future.

Radiative cooling assisted self-sustaining and highly efficient moisture energy harvesting

Harvesting electricity from ubiquitous water vapor represents a promising route to alleviate the energy crisis. However, existing studies rarely comprehensively consider the impact of natural environmental fluctuations on electrical output. Here, we demonstrate a bilayer polymer enabling self-sustaining and highly efficient moisture-electric generation from the hydrological cycle by establishing a stable internal directed water/ion flow through thermal exchange with the ambient environment. Specifically, the radiative cooling effect of the hydrophobic top layer prevents the excessive daytime evaporation from solar absorption while accelerating nighttime moisture sorption. The introduction of LiCl into the bottom hygroscopic ionic hydrogel enhances moisture sorption capacity and facilitates ion transport, thus ensuring efficient energy conversion. A single device unit (1 cm2) can continuously generate a voltage of ~0.88 V and a current of ~306 μA, delivering a maximum power density of ~51 μW cm-2 at 25 °C and 70% relative humidity (RH). The device has been demonstrated to operate steadily outdoors for continuous 6 days.

Hydrovoltaic Electricity Generator with Hygroscopic Materials: A Review and New Perspective

The global energy crisis caused by the overconsumption of nonrenewable fuels has prompted researchers to develop alternative strategies for producing electrical energy. In this review, a fascinating strategy that simply utilizes water, an abundant natural substance throughout the globe and even in air as moisture, as a power source is introduced. The concept of the hydrovoltaic electricity generator (HEG) proposed herein involves generating an electrical potential gradient by exposing the two ends of the HEG device to dissimilar physicochemical environments, which leads to the production of an electrical current through the active material. HEGs, with a large variety of viable active materials, have much potential for expansion toward diverse applications including permanent and/or emergency power sources. In this review, representative HEGs that generate electricity by the mechanisms of diffusion, streaming, and capacitance as case studies for building a fundamental understanding of the electricity generation process are discussed. In particular, by comparing the use and absence of hygroscopic materials, HEG mechanism studies to establish active material design principles are meticulously elucidated. The review with future perspectives on electrode design using conducting nanomaterials, considerations for high performance device construction, and potential impacts of the HEG technology in improving the livelihoods are reviewed.

Construction of Janus structures on thin silk fabrics via misting for wet-thermal comfort and antimicrobial activity

Owing to their small fiber diameter (10-15 μm), silk fabrics are always thin (32-90 g m-2). Therefore, construction of the Janus surfaces of silk fabrics that possess excellent multifunctionality remains a formidable challenge. Herein, first, silk fabrics were grafted using glycidyltrimethylammonium chloride to form a superhydrophilic surface (G-side). Then, a unilateral hydrophobic surface (O-side) was readily fabricated by mist coating octadecyltrichlorosilane-functionalized SiO2 nanoparticles (NPs) to produce hierarchical surface textures. To prevent NP penetration from the G-side to the O-side, a "fireproof isolation" method was employed. Consequently, Janus silk fabrics (JanSFs) bearing asymmetric wettability were prepared, and their wetting gradient could be conveniently regulated. With the mist time ranging from 4 to 7 min, the unidirectional transport index and efficiency of the unidirectional water transport increased and decreased by 13.2 and 10.4 times, respectively. Sweat could be effectively drained away from human skin to ensure that the skin was dry and comfortable. Compared with the surface temperature of the raw fabric, the raw fabric of JanSFs increased by 2.7 °C. Furthermore, the breathability of JanSF was negligibly affected, and the outer O-side of the JanSF showed substantial antibacterial activity. This study is important for designing JanSFs that exhibit unidirectional water transport.

Nanoengineering Natural Leather for Dynamic Thermal Management and Electromagnetic Interference Shielding

Unpredictable and extreme weather conditions, along with increasing electromagnetic pollution, have resulted in a significant threat to human health and productivity, causing irreversible damage to society's well-being and economy. However, existing personal temperature management and electromagnetic protection materials lack adaptability to dynamic environmental changes. To address this, a unique asymmetric bilayer leather/a-MWCNTs/CA fabric is developed by vacuum-infiltrating interconnected a-MWCNTs networks into natural leather's microfiber backbone and spraying porous acetic acid (CA) on the reverse side. Such fabric achieves simultaneous passive radiation cooling, heating, and anti-electromagnetic interference functions without external energy input. The fabric's cooling layer has high solar reflectance (92.0%) and high infrared emissivity (90.2%), providing an average subambient radiation cooling effect of 10 °C, while the heating layer has high solar absorption (98.0%), enabling excellent passive radiative heating and effective compensation for warming via Joule heating. Additionally, the fabric's 3D conductive a-MWCNTs network provides electromagnetic interference shielding effectiveness of 35.0 dB mainly through electromagnetic wave absorption. This multimode electromagnetic shielding fabric can switch between cooling and heating modes to adapt to dynamic cooling and heating scenarios, providing a new avenue for sustainable temperature management and electromagnetic protection applications.