Explore the vast range of titles available.

The sun (∼6,000 K) and outer space (∼3 K) are two significant renewable thermodynamic resources for human beings on Earth. The solar thermal conversion by photothermal (PT) and harvesting the coldness of outer space by radiative cooling (RC) have already attracted tremendous interest. However, most of the PT and RC approaches are static and monofunctional, which can only provide heating or cooling respectively under sunlight or darkness. Herein, a spectrally self-adaptive absorber/emitter (SSA/E) with strong solar absorption and switchable emissivity within the atmospheric window (i.e., 8 to 13 μm) was developed for the dynamic combination of PT and RC, corresponding to continuously efficient energy harvesting from the sun and rejecting energy to the universe. The as-fabricated SSA/E not only can be heated to ∼170 °C above ambient temperature under sunshine but also be cooled to 20 °C below ambient temperature, and thermal modeling captures the high energy harvesting efficiency of the SSA/E, enabling new technological capabilities.

Passive radiative cooling is an energy-free cooling method by exchanging thermal radiation with the cold universe through the transparent atmospheric window. Spectrum tailoring of the radiative cooler is the key to daytime radiative cooling in previously reported works. In addition, radiative coolers with large-scale fabrication and self-cleaning characteristics should be further developed to improve their industrial applicability. Herein, we propose a bilayer radiative cooling coating with the superhydrophobic property and a scalable process, by covering TiO /acrylic resin paint with a silica/poly(vinylidene fluoride-co-hexafluoropropylene) (SiO /P(VdF-HFP)) composite masking layer. The strong Mie scattering in TiO /acrylic resin paint contributes to high solar reflection, while the SiO /P(VdF-HFP) masking layer is responsible for superhydrophobicity and synergetic solar reflection in the ultraviolet band, resulting in an effective solar reflectivity of 94.0 % with an average emissivity of 97.1 % and superhydrophobicity with a water contact angle of 158.9°. Moreover, the as-fabricated coating can be cooled to nearly 5.8 °C below the temperature of commercial white paint and 2.7 °C below the local ambient temperature under average solar irradiance of over 700 W m . In addition, yearly energy saving of 29.0 %–55.9 % can be achieved after the coating is applied to buildings in Phoenix, Hong Kong, Singapore, Guangzhou, and Riyadh.

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

In most near‐infrared atmospheric windows, absorption of solar radiation is dominated by the water vapor self‐continuum, and yet there is a paucity of measurements in these windows. We report new laboratory measurements of the self‐continuum absorption at temperatures between 293 and 472 K and pressures from 0.015 to 5 atm in four near‐infrared windows between 1 and 4 μm (10000–2500 cm−1); the measurements are made over a wider range of wavenumbers, temperatures, and pressures than any previous measurements. They show that the self‐continuum in these windows is typically one order of magnitude stronger than given in representations of the continuum widely used in climate and weather prediction models. These results are also not consistent with current theories attributing the self‐continuum within windows to the far wings of strong spectral lines in the nearby water vapor absorption bands; we suggest that they are more consistent with water dimers being the major contributor to the continuum. The calculated global average clear‐sky atmospheric absorption of solar radiation is increased by ∼0.75 W/m2 (which is about 1% of the total clear‐sky absorption) by using these new measurements as compared to calculations with the MT_CKD‐2.5 self‐continuum model. Key Points Water vapor self‐continuum is derived from lab measurements in near‐IR windows The measured continuum is dramatically stronger than MT_CKD or far‐wing models This result changes calculated clear‐sky absorption of solar radiation by 1%–2%

The traditional telecommunications band performs poorly in harsh weather conditions due to atmospheric absorption. In recent years, researchers have begun to study optical communication through atmospheric windows, and optical switches are an essential component of optical communication. A broadband atmospheric window optical switch was proposed based on Vanadium dioxide and magnetic polaritons (MP). It is formed by the stacking of two metal-dielectric-metal structures. The simulation results show that the modulation depth can reach 98.38%, and the extinction ratio is 17.93 dB. By calculating the magnetic field, we confirmed that the reason for the “off” mode is the coupling between the different MP modes, while the “on” mode is the excitation of MP. The optical switch we proposed may be applied to radiation cooling and optical satellite communication.

We propose a highly efficient broadband tunable metamaterial infrared absorption device. The design is modeled using the three-dimensional finite element method for the absorption device. The results show that the absorption device captures over 90% of the light in the wavelength range from 6.10 μm to 17.42 μm. We utilize VO2’s phase change property to adjust the absorption device, allowing the average absorption level to vary between 20.61% and 94.88%. In this study, we analyze the electromagnetic field distribution of the absorption device at its peak absorption point and find that the high absorption is achieved through both surface plasmon resonance and Fabry–Perot cavity resonance. The structural parameters of the absorption device are fine-tuned through parameter scanning. By comparing our work with previous studies, we demonstrate the superior performance of our design. Additionally, we investigate the polarization angle and incident angle of the absorption device and show that it is highly insensitive to these factors. Importantly, the simple structure of our absorption device broadens its potential uses in photodetection, electromagnetic stealth, and sensing.

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

Adjusting the band gap of armchair graphene nanoribbons (AGNRs) in the IR detection area is so noticeable due to the importance of atmospheric IR windows in optoelectronic industries. So, using the first-principle calculations, the band gap energy of AGNRs from three different families are considered in the presence of nitrogen (N) and boron (B) atoms, computationally. The result of the substitutional doping optimization indicates that the doped AGNRs with N atoms at the edge of the ribbon, and with B atoms at the middle of the ribbon are energetically the most stable state. Our electronic calculations show that the n-type and p-type semiconductors have been produced, which can be promising candidates for optoelectronic devices such as photodetectors with performance in the IR detection area. Furthermore, our results show that doped AGNRs have application in 1–3 µm, 3–5 µm and 8–14 µm atmospheric windows.

Microfluidic devices have enormous potential and a wide range of applications. However, most applications end up as chip-in-a-lab systems because of power source constraints. This work focuses on reducing the reliance on the power network and expanding on the concept of a lab-on-a-chip for microfluidic devices. A cellulose-based radiator to reflect infrared (IR) radiation with wavelengths within the atmospheric window (8–13 µm) into outer space was fabricated. This process lowered the temperature inside the insulated environment. The difference in temperature was used to power a thermoelectric generator (TEG) and generate an electric current. This electric current was run through a DC-DC transformer to increase the voltage before being used to perform electrical cell lysis with a microfluidic device. This experimental setup successfully achieved 90% and 50% cell lysis efficiencies in ideal conditions and in field tests, respectively. This work demonstrated the possibility of utilizing the unique characteristics of a microfluidic device to perform an energy-intensive assay with minimal energy generated from a TEG and no initial power input for the system. The TEG system also required less maintenance than solar, wind, or hydroelectricity. The IR radiation process naturally allows for more dynamic working conditions for the entire system.

Interminable surveillance and reconnaissance through various sophisticated multispectral detectors present threats to military equipment and manpower. However, a combination of detectors operating in different wavelength bands (from hundreds of nanometers to centimeters) and based on different principles raises challenges to the conventional single-band camouflage devices. In this paper, multispectral camouflage is demonstrated for the visible, mid-infrared (MIR, 3–5 and 8–14 μm), lasers (1.55 and 10.6 μm) and microwave (8–12 GHz) bands with simultaneous efficient radiative cooling in the non-atmospheric window (5–8 μm). The device for multispectral camouflage consists of a ZnS/Ge multilayer for wavelength selective emission and a Cu-ITO-Cu metasurface for microwave absorption. In comparison with conventional broadband low emittance material (Cr), the IR camouflage performance of this device manifests 8.4/5.9 °C reduction of inner/surface temperature, and 53.4/13.0% IR signal decrease in mid/long wavelength IR bands, at 2500 W ∙ m −2 input power density. Furthermore, we reveal that the natural convection in the atmosphere can be enhanced by radiation in the non-atmospheric window, which increases the total cooling power from 136 W ∙ m −2 to 252 W ∙ m −2 at 150 °C surface temperature. This work may introduce the opportunities for multispectral manipulation, infrared signal processing, thermal management, and energy-efficient applications. Manipulating electromagnetic waves to camouflage objects is an important tool. Here, the authors present a camouflage that covers a wide range of frequencies based on multilayer and metasurface technologies.