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Polymeric membrane ion-selective electrodes (ISEs) have been widely used in environmental monitoring. However, in complicated marine environments, marine biofouling usually becomes a sticky problem for these electrodes. Herein, for the first time, a novel maintenance-free antifouling potentiometric marine sensor based on a self-polishing coating (SPC) is proposed. The SPC is synthesized by using the seeded emulsion polymerization method based on the triisopropylsilyl methacrylate monomer as the regulator of the self-renewal rate. This coating can be simply modified onto the electrode surface by drop-casting. The silyl acrylate side groups of the obtained SPC on the sensor surface can be hydrolyzed in the marine alkaline medium. The shear movement of seawater driven by sea waves, wind, gravity, or vibration removes the leftover (fouled) brittle polymer backbone and thus the fouling marine microorganisms. As a proof-of-concept experiment, a polymeric membrane Ca2+-ISE is chosen as a model. Compared to the unmodified electrode, the SPC-coated Ca2+-ISE exhibits remarkable improved antifouling properties in terms of superior anti-adhesive abilities towards marine microorganisms, such as bacterial cells and algae and excellent long-term stability even in the presence of high levels of marine microorganisms. Since no additional manual maintenance is required for maintaining the antifouling abilities of the sensor, the proposed self-polishing sensor may lay an important foundation for construction of unattended long-term potentiometric monitoring systems in real marine environments. [ABSTRACT FROM AUTHOR]

Polymeric membrane ion-selective electrodes (ISEs) have been widely used in environmental monitoring. However, in complicated marine environments, marine biofouling usually becomes a sticky problem for these electrodes. Herein, for the first time, a novel maintenance-free antifouling potentiometric marine sensor based on a self-polishing coating (SPC) is proposed. The SPC is synthesized by using the seeded emulsion polymerization method based on the triisopropylsilyl methacrylate monomer as the regulator of the self-renewal rate. This coating can be simply modified onto the electrode surface by drop-casting. The silyl acrylate side groups of the obtained SPC on the sensor surface can be hydrolyzed in the marine alkaline medium. The shear movement of seawater driven by sea waves, wind, gravity, or vibration removes the leftover (fouled) brittle polymer backbone and thus the fouling marine microorganisms. As a proof-of-concept experiment, a polymeric membrane Ca2+-ISE is chosen as a model. Compared to the unmodified electrode, the SPC-coated Ca2+-ISE exhibits remarkable improved antifouling properties in terms of superior anti-adhesive abilities towards marine microorganisms, such as bacterial cells and algae and excellent long-term stability even in the presence of high levels of marine microorganisms. Since no additional manual maintenance is required for maintaining the antifouling abilities of the sensor, the proposed self-polishing sensor may lay an important foundation for construction of unattended long-term potentiometric monitoring systems in real marine environments. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Stealth performance plays an increasingly important role in the evaluation of aircraft performance, while achieving excellent stealth performance in multiple frequency bands simultaneously remains a crucial challenge. Herein, a visible transparent wideband microwave absorber with infrared camouflage function is theoretically presented and experimentally demonstrated. The sample is composed of two radar absorption layers (RALs) and an infrared shielding layer (IRSL). In addition, the magnetic resonance model and the ohmic loss model are employed to strengthen the absorption of the designed RALs >90% in a broadband frequency range of 7–23 GHz with a relative bandwidth of 106.7%, and an average visible transmittance of ≈60%. Furthermore, IRSL is achieved by a designable digital frequency selective surface (FSS), which promotes a compatible design between infrared camouflaged emissivity and microwave absorption. These peculiar properties not only verify the feasibility of the proposed strategy for achieving suitable artificially designed IR digital camouflage patterns to meet various thermal camouflage environments, but also have promising application prospects in multispectral stealth. The additional visible light transparent feature makes it useful in compatible camouflage‐stealth facilities when requiring observing and operating in optical windows. [ABSTRACT FROM AUTHOR]

Metasurfaces composed of subwavelength structure arrays provide a diverse and powerful platform for generation of complicated electromagnetic (EM) fields and wavefronts manipulation and have triggered an unprecedented research upsurge in electromagnetism with the development of computer‐generated holography (CGH). Different from conventional scalar holograms only containing amplitude and phase properties, a vectorial hologram that benefits from the maneuverability of polarization of EM fields exhibits more immeasurable application potential and is simultaneously regarded as an urgent requirement. In this work, assisted by single completely spin‐decoupled meta‐particles, which perfectly combine the functions of simultaneous and independent amplitude and phase modulation of orthogonal polarization states containing left‐ and right‐handed circularly polarized (LCP&RCP) components, a vectorial hologram induced through eigenstates degeneracy with the ability of encoding arbitrary polarization is proposed in the microwave region. As the proof of concept, eight distinct holograms with specified polarizations and six‐channel polarization‐multiplexed hologram display are fabricated and characterized, further showcaing the versatility of the approach for the customization of arbitraty polarization and integration of reconstructed patterns. With the advantages of multi‐controllability and ultra‐compactness, the constructed monolayer completely spin‐decoupled paradigm for vectorial regulation may find prospective application aspects in spin detection, target perception, multi‐channel data encryption, and many other related fields. [ABSTRACT FROM AUTHOR]

Protecting human health from fine particulate matter (PM) pollution is the ambitious goal of clean air actions, but current control strategies largely ignore the role of source-specific PM toxicity. Here, we proposed health-oriented control strategies by integrating the unequal toxic potencies of the most polluting industrial PMs. Iron and steel industry (ISI)-emitted PM2.5 exhibit about one order of magnitude higher toxic potency than those of cement and power industries. Compared with the current mass-based control strategy (prioritizing implementation of ultralow emission standards in the power sector), the proposed health-oriented control strategy (priority control of the ISI sector) could generate 5.4 times higher reduction in population-weighted toxic potency-adjusted PM2.5 exposure among polluting industries in China. Furthermore, the marginal abatement cost per unit of toxic potency-adjusted mass of ISI-emitted PM2.5 is only a quarter of that of the other two sectors under ultralow emission scenarios. We highlight that a health-oriented air pollution control strategy is urgently required to achieve cost-effective reductions in particulate exposure risks. Health-oriented emissions reduction in China focusing on the iron and steel industry can reduce costs by 1.56 billion dollars while lowering the population-weighted toxic potency-adjusted exposure risk. [ABSTRACT FROM AUTHOR]

The fifth-generation (5G) wireless communication has an urgent need for target tracking. Digital programmable metasurface (DPM) may offer an intelligent and efficient solution owing to its powerful and flexible controls of electromagnetic waves and advantages of lower cost, less complexity and smaller size than the traditional antenna array. Here, we report an intelligent metasurface system to perform target tracking and wireless communications, in which computer vision integrated with a convolutional neural network (CNN) is used to automatically detect the locations of moving targets, and the dual-polarized DPM integrated with a pre-trained artificial neural network (ANN) serves to realize the smart beam tracking and wireless communications. Three groups of experiments are conducted for demonstrating the intelligent system: detection and identification of moving targets, detection of radio-frequency signals, and real-time wireless communications. The proposed method sets the stage for an integrated implementation of target identification, radio environment tracking, and wireless communications. This strategy opens up an avenue for intelligent wireless networks and self-adaptive systems.The authors present an intelligent metasurface system that uses a target detection algorithm combined with a depth camera, to automatically detect the position of moving targets and achieve real-time wireless communications. The system can operate for multiple targets in limited ambient light, outdoor and other realistic environments. [ABSTRACT FROM AUTHOR]

In this article, we propose a method of achieving broadband decoupling between large antenna arrays using magnetic metasurface (MM). To realize broadband isolation performance, the MM consists of four sub‐regions composed periodic arrays of split‐ring resonators (SRRs). The four sub‐regions can achieve negative permeability in sequential frequency ranges, which can together cover the whole X‐band by proper combinations. When the MM is placed between the antenna arrays, the propagation of the coupled electromagnetic waves will be suppressed due to the negative permeability, so the isolation between the antenna arrays will be enhanced. For simplicity, the broadband decoupling performance of MM is verified by using patch antenna elements. Prototypes were fabricated and measured. Both simulated and measured results show that when the distance between the two antenna elements is about half a meter, the isolation can be enhanced by at least 25.0 dB in the whole X‐band, which convincingly verifies our method. This work provides an alternative to enhancing isolation between broadband antenna arrays and may find applications in electromagnetic compatibility of integrated masts, base stations, and so on. [ABSTRACT FROM AUTHOR]

Vortex beam carrying orbital angular momentum (OAM) has been experiencing a research upsurge attributed to its excellent communication capability, which also boosts the development of the OAM technology and promotes the application of the OAM generator. However, most of the existing designs of the OAM generators can only produce a small number of diverse OAM modes, and restrict the channel capacity of single OAM generator. Herein, an appealing strategy of six‐mode OAM generator based on helicity‐assisted full‐space metasurface is proposed to generate up to six diverse OAM modes by altering the polarization state, illumination region, and incidence direction of incident waves. Significantly, the designed OAM generator has high communication security because of its great information entropy, and the generated OAM modes possess the characteristics of high purity and low crosstalk which result from the orthogonal polarization states and unequal deflection angles of produced vortex beams. A proof‐of‐concept prototype is constructed to corroborate the validity of our methodology, and the results of simulations and experiments are in excellent agreement with theoretical predictions. This fire‐new OAM generator will possess a promising application prospect in communication systems, and may also provide an efficacious method to design multifunctional devices. [ABSTRACT FROM AUTHOR]

Surface plasmon polaritons (SPPs) have great applications in imaging, sensing, waveguide, and communication. Especially in the trending of electromagnetic (EM) metastructure field, researchers used the phase gradient design to achieve the efficient surface wave propagating performance ranging from GHz to THz. However, due to the intrinsic coupling interference from the current structure design, the phase and amplitude of different polarization are hard to freely manipulate simultaneously, making the design of multifunctional channels SPPs still a challenging project. Here, an anisotropic structure is proposed to realize independent control of both polarization and amplitude along different component of the wavefront. By analyzing the polarization dependent mechanism, the hexagon and half‐hexagon meta‐atom are introduced to the coupler structure to tailor the desired phase gradient along different directions under different polarized EM waves. Then the dispersion of coupler is further coupled with the propagating patch metasurface by optimization algorithm. As a result, the multifunctional SPP is achieved, and the multimode excitation can be generated under both linear and circular polarized incidence. Both simulation and experiment validate the effectiveness and wideband of spoof SPPs excitation performance, verifying that this method reduces the excitation condition of surface wave and improves the multiplexing effect of propagation channel. [ABSTRACT FROM AUTHOR]

Surface waves (SWs) can be coupled by phase gradient metasurfaces (PGMs) with high efficiency, but this methodology still suffers from inherent defects of narrow bandwidth, changeless coupled mode, difficult separation of hybrid modes SWs, and uncontrollable propagation direction. In this article, a series of innovative designs is proposed by combining different Pancharatnam–Berry (PB) PGMs with appointed phase distribution principles to resolve PGMs SWs couplers’ above problems. Both the simulated and measured results verify that the broadband conventional SWs coupler can couple transverse magnetic (TM) mode SWs under $x$ -polarized incidence and the broadband extraordinary SWs coupler can couple TM mode SWs under $y$ -polarized incidence in 8.5–11.5 GHz. By integrating these two SWs couplers, a bifunctional SWs coupler is obtained to couple TM mode SWs to the left and transverse electric (TE) mode SWs to the right simultaneously under $x$ -polarized incidence. Furthermore, another two SWs couplers are designed to excite TM mode SWs with 30° and 45° slant directions under $x$ -polarized incidence in 8.5–11.5 GHz, which indicates that coupled SWs’ wavefront direction can be controlled flexibly in a wide bandwidth. The above SWs couplers are proved to work with relatively high coupling efficiencies and have great potential in engineering applications. [ABSTRACT FROM AUTHOR]

Metasurfaces have provided unprecedented freedom for manipulating electromagnetic waves. In metasurface design, massive meta-atoms have to be optimized to produce the desired phase profiles, which is time-consuming and sometimes prohibitive. In this paper, we propose a fast accurate inverse method of designing functional metasurfaces based on transfer learning, which can generate metasurface patterns monolithically from input phase profiles for specific functions. A transfer learning network based on GoogLeNet-Inception-V3 can predict the phases of 28×8 meta-atoms with an accuracy of around 90%. This method is validated via functional metasurface design using the trained network. Metasurface patterns are generated monolithically for achieving two typical functionals, 2D focusing and abnormal reflection. Both simulation and experiment verify the high design accuracy. This method provides an inverse design paradigm for fast functional metasurface design, and can be readily used to establish a meta-atom library with full phase span. The design and optimization of a metasurface is a computationally- and time-consuming effort. Here, the authors propose a neural network-based algorithm for functional metasurface design, and demonstrate it for some functional metasurfaces. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide hollow microspheres (rGO HMS) were encapsulated with gold nanoparticles (AuNPs) by spray drying. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy were used to characterize the AuNP/rGO HMS. When placed on a glassy carbon electrode (GCE), it exhibits excellent electrochemical catalytic properties towards the oxidation of nitrite. The electrocatalytic properties were studied using various electrochemical techniques. Compared to AuNP-decorated graphene sheet based electrodes documented in the literature, the one presented here provides a larger surface area. This enhances the catalytic activity towards nitrite. The electrode, typically operated at a working potential of 0.82 V (vs. SCE), has a linear response in the 5.0 μM to 2.6 mM nitrate concentration range, and a detection limit as low as 0.5 μM (at an S/N ratio of 3). [ABSTRACT FROM AUTHOR]