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•Developed the electrochromic and thermal-control broadband stealth devices.•Revealed the influencing mechanisms of AZO/Ag/AZO electrodes on spectral characteristics.•Integrates multiple optical mechanisms to modulate visible-infrared stealth characteristics.

Flexible manipulation of surface waves (SWs) radiation has been continuously intriguing enormous interests of researchers due to its promising application prospects, and metasurfaces exhibit unparalleled capability to efficiently control SWs radiation. However, existing schemes still suffer from the bottlenecks of single radiation channel and immutable radiation pattern, which are difficult to satisfy the requirements of high-integration intelligent metadevices. Herein, an ingenious strategy of the SWs radiation metadevice is proposed to independently and dynamically manipulate SWs directional radiation in four polarization channels. The waveguide port and the guided wave structure are designed to excite and propagate the desired SWs, and the programmable coding metasurface can independently convert SWs into x-polarized radiation waves, y-polarized radiation waves, left-handed circular polarized radiation waves and right-handed circular polarized radiation waves and dynamically control the corresponding radiation angles by adjusting the ON/OFF states of two positive-intrinsic-negative diodes in each spin-decoupled meta-atom. Numerous simulation and experimental results of the proof-of-concept prototype are in good agreement with the theoretical predictions, which verify the feasibility of our proposed methodology. The innovative design of four-channel SWs radiation metadevice with high radiation efficiency and broad radiation bandwidth offers an excellent platform for flexibly manipulating SWs radiation, and possesses tremendous potential in engineering application.

The infrared (IR) stealth and visible stealth have different spectral response requirements, resulting in the difficulty in the coordination of the design of multispectral compatible stealth material, so it is necessary to develop selective regulation technologies of optical properties. Based on an ITO/Ag/ITO stacked film structure integrating induced transmission, radiation suppression, and other optical synergistic effects, a new type of superstructured thin film material with transparent infrared stealth was proposed. A collaborative design method integrated with high visible transmission and low IR radiation was established, the influence mechanism of microstructure characteristics on visible transmission spectrum and IR reflection spectrum was interpreted, then the design of highly transparent infrared stealth material was optimized, and its compatible stealth performance was tested and characterized. Research showed that visible transmission was contingent upon the coupling and matching between the semiconductor layer and the metal layer, while the IR radiation suppression mainly depended on the metal layer. The optimized ITO/Ag/ITO superstructured film with a thickness of 40/12/40 nm possesses high background perspective reproduction, high-temperature IR radiation suppression, and high flexible conformal ability with curved surface. The research results can provide indispensable technical support for the design and application of multispectral compatible stealth material.

In this communication, we propose a block-and-guide method of enhancing isolation between Vivaldi antennas in the whole X-band using hyperbolic metasurface (HMS). The HMS consists of periodic parallel metallic strips patterned on a thin dielectric substrate. Due to its strong anisotropy, the HMS exhibits a passband for electromagnetic (EM) waves propagating along the strip direction while a stopband for EM waves propagating along the orthogonal direction. When the HMS is placed close to the opening end of the Vivaldi antenna, the broadside radiation of the antenna can be suppressed while the endfire radiation is almost unaffected, leading to enhanced isolation between adjacent antennas. Rather than adding auxiliaries in between antennas, the HMS can be readily integrated into the antenna radiator structure, which is more favorable for practical applications, especially in compact spaces. To verify this method, the prototype was fabricated and measured. Both simulated and measured results show that when the distance is $0.5\lambda _{0}$ ( $\lambda _{0}$ is the free-space wavelength of 10.0 GHz) between two Vivaldi antenna elements, the isolation can be increased by at least 10.0 dB in the whole X-band. This work provides an alternative to enhance isolation between wideband endfire antennas and may find applications in radar, wireless communication, and so on.

Achieving the conversion from surface waves (SWs) to propagating waves has captivated long-standing interest, and various ingenious metasurfaces benefiting from the powerful control capability for electromagnetic waves are able to realize efficient SWs directional radiation. Nevertheless, most existing schemes still suffer from the bottlenecks of single radiation channel, uncontrollable radiation intensity, and immutable radiation pattern, which immensely hinder their practical application in high-integration intelligent devices. Herein, a series of appealing strategies are proposed to achieve the dual-channel SWs directional radiation with customizable radiation intensity and switchable radiation pattern. The dual-channel SWs radiation metadevice based on the phase modulation metasurface is designed to directionally radiate SWs in left-handed circular polarized channel and right-handed circular polarized channel and possesses the broadband frequency scanning characteristic. More strikingly, the intensity-customizable dual-channel SWs radiation metadevice loaded with lumped resistors can control the realized gain of two circular polarized radiation beams, and the pattern-switchable dual-channel SWs radiation metadevice loaded with PIN diodes can dynamically adjust the radiation direction of the radiation beams. Numerous simulations and experiments of the proof-of-concept prototypes with modular design corroborate the theoretical predictions. Our methodology shows unprecedented flexibility in regulating SWs directional radiation and has enormous potential in engineering applications.

Nowadays, using a polymeric membrane ion-selective electrode (ISE) to achieve reliable ion sensing in complex samples remains challenging because of electrode fouling. To address this challenge, we describe a polymeric membrane ISE with excellent anti-fouling and self-cleaning properties based on surface covalent modification of an anatase TiO2coating. Under ultraviolet illumination, the reactive oxygen species produced by photocatalytic TiO2can not only kill microorganisms but also degrade organic foulants into carbon dioxide and water, and a formed superhydrophilic film can effectively prevent the adsorption of foulants, thus inhibiting the occurrence of biofouling and organic fouling of the sensors. More importantly, residual foulants could be fully self-cleaned through the flow of water droplets. By using Ca2+-ISE as a model, an anti-fouling polymeric membrane potentiometric sensor has been developed. Compared to the unmodified electrode, the TiO2-coated Ca2+-ISE exhibits remarkably improved anti-biofouling properties with a low bacterial adhesion rate of 4.74% and a high inhibition rate of 96.62%. In addition, the proposed electrode displays unique properties of anti-organic dye fouling and a superior self-cleaning ability even after soaking in a concentrated bacterial suspension of 109CFU mL–1for 60 days. The present approach can be extended to improve the fouling resistance of other electrochemical or optical membrane sensors and is promising for the construction of contamination-free sensors.

Coal preparation is effective in controlling primary mercury emissions in coal combustion systems; however, the combustion of coal preparation byproducts may cause secondary emissions. The inconsistent coal preparation statistics, unclear mercury distribution characteristics during coal preparation, and limited information regarding the byproduct utilization pathways lead to great uncertainty in the evaluation of the effect of coal preparation in China. This study elucidated the mercury distribution in coal preparation based on the activity levels of 2886 coal preparation plants, coal mercury content database, tested mercury distribution factors of typical plants, and then traced the mercury flows and emissions in the downstream sectors using a cross-industry mercury flow model. We found that coal preparation altered the mercury flows by reducing 68 tonnes of mercury to sectors such as coking and increasing the flows to byproduct utilization sectors. Combusting cleaned coal rather than raw coal reduced the mercury emissions by 47 tonnes; however, this was offset by secondary mercury emissions. Coal gangue spontaneous combustion and the cement kiln coprocessing process were dominant secondary emitters. Our results highlight the necessity of whole-process emission control of atmospheric mercury based on flow maps. Future comprehensive utilization of wastes in China should fully evaluate the potential secondary mercury emissions.

This study developed an up-to-date and point-source-based inventory of mercury (Hg) releases to water in China by applying probabilistic release factors that combined industry removal efficiencies, reuse of reclaimed water, and receiving water types. In 2017, the national mercury release to water was estimated to be 50 (35–66) tons, in which 47%, 8%, 7%, and 25% were from nonferrous metal smelting, vinyl chloride monomer (VCM) production, coal-fired boilers, and domestic sewage, respectively. Approximately 95% of mercury was released to inland rivers, and the rest was discharged to lakes or coastal water. The significant sources were identified based on their mercury releases to water. The control of mercury release to water in China shall focus on zinc smelting plants, municipal sewage treatment plants, and the VCM production process. For zinc smelting plants, China can tighten the limit of mercury concentration in discharged wastewater and combine Hg-catcher device in traditional integrated treatment. For municipal sewage treatment plants and the VCM production process, promoting processes of Hg-free production can reduce mercury inputs at the source. Our study provides insights for other parties to identify the relevant sources of mercury release to water and to conduct control measures, so as to promote the global convention implementation.

China took aggressive air pollution control measures from 2013 to 2017, leading to the mitigation of atmospheric mercury pollution as a cobenefit. This study is the first to systematically evaluate the effect of five major air pollution control measures in reducing mercury emissions, the total gaseous mercury (TGM) concentration and mercury deposition flux (FLX) for unit emissions reduction. From 2013 to 2017, China’s mercury emissions decreased from 571 to 444 tons, resulting in a 0.29 ng m–3decrease in the TGM concentration, on average, and in a 17 μg m–2yr–1decrease in FLX. Ultralow emission renovations of coal-fired power plants are identified as the most effective emission abatement measure. As a result of this successful measure, coal-fired power plants are no longer the main mercury emitters. In 2017, the cement clinker sector became the largest emitter due to the use of less effective mercury removal measures. However, in terms of the mitigated TGM concentration and FLX levels per unit emission abatement, newly built wet flue gas desulfurization (WFGD) systems in coal-fired industrial boilers have become particularly effective in decreasing FLX levels. Therefore, to effectively reduce atmospheric mercury pollution in China, prioritizing mercury emissions control of cement clinkers and coal-fired industrial boilers is recommended.

The power of controlling objects with mind has captivated a popular fascination to human beings. One possible path is to employ brain signal collecting technologies together with emerging programmable metasurfaces (PM), whose functions or operating modes can be switched or customized via on-site programming or pre-defined software. Nevertheless, most of existing PMs are wire-connected to users, manually-controlled and not real-time. Here, we propose the concept of remotely mind-controlled metasurface (RMCM) via brainwaves. Rather than DC voltage from power supply or AC voltages from signal generators, the metasurface is controlled by brainwaves collected in real time and transmitted wirelessly from the user. As an example, we demonstrated a RMCM whose scattering pattern can be altered dynamically according to the user’s brain waves via Bluetooth. The attention intensity information is extracted as the control signal and a mapping between attention intensity and scattering pattern of the metasurface is established. With such a framework, we experimentally demonstrated and verified a prototype of such metasurface system which can be remotely controlled by the user to modify its scattering pattern. This work paves a new way to intelligent metasurfaces and may find applications in health monitoring, 5G/6G communications, smart sensors, etc.

Amplitude–phase control for circular polarized (CP) waves is experiencing a research upsurge in electromagnetics owing to the kaleidoscopic electromagnetic responses and promising application prospects of circular polarizations, and chiral metasurfaces are more facile to achieve a series of intriguing chiral phenomena than natural materials. However, it is difficult for most existing chiral metasurfaces to independently tailor the amplitude and phase of left-handed circular polarized and right-handed circular polarized waves at the same frequency as they suffer the drawbacks of large thickness, multiple layers, and complex structure. Herein, an innovative strategy of single-layer achiral metasurfaces of thickness 0.13λ0is proposed to independently and simultaneously manipulate the amplitude and phase of orthogonal CP waves. As a proof of concept, an amplitude and phase controlled dual-channel meta-hologram is designed to reconstruct diverse images with high fidelity under orthogonal CP illumination, and the simulated and experimental results collectively validate the availability of our methodology. Significantly, the meta-hologram is also applicable to full polarization states according to the decomposition of electromagnetic waves. The inspiring design of single-layer achiral metasurfaces provides a simple and effective approach to explore chiral effects, and they possess enormous application potential in multitudinous microwave devices.

Metasurfaces with simultaneously and independently controllable amplitude and phase have provided a higher degree of freedom in manipulating electromagnetic (EM) waves. Compared with phase- or amplitude-only modulation, the capability of simultaneously controlling the phase and amplitude of EM waves can enable holography with a higher resolution. However, this drastically increases the design complexity of holographic metasurfaces, and the design process is usually quite time-consuming. In this paper, we propose an inverse design of meta-atoms that can simultaneously and independently tailor the phase and amplitude of transmitted waves using customized deep ResNet while eliminating the coupling of parameters. To demonstrate the design method, two holographic metasurfaces were designed using the trained network without the need for parameter sweeping, which will significantly enhance design efficiency. Prototypes were fabricated and measured. Both the simulated and measured results show that high-resolution holography is obtained, which sufficiently verifies the reliability of the design method. Our work paves the way for the intelligent design of metasurfaces and can also be applied to the design of other artificial materials or surfaces.