ABSTRACT Programmable metasurfaces (PMs) provide a compelling platform for human sensing under conditions where vision‐based methods fail. However, conventional metasurface sensing relies exclusively on electromagnetic scattering data captured at the isolated and current time instant. Lacking integration with the historical temporal context, these single‐frame approaches suffer when severe indoor multipath fading distorts the transient scattering signatures, leading to estimation failures during deep fading events. To address this limitation, an intelligent PM system is proposed utilizing a multi‐frame spatiotemporal fusion approach, which treats human motion as a continuous evolution process. By exploiting the temporal dependencies across sequential frames through a Spatiotemporal Metasurface Pose Network (ST‐MetaPose), the system autonomously compensates for deeply faded instantaneous observation using kinematic context. For experimental validation, a prototype system featuring a 1‐bit PM consisting of a 30 × 30 array operating at 11.4 GHz is implemented. Experimental results demonstrate robust, continuous three‐dimensional 18‐keypoint pose estimation at 20 Hz, achieving a mean per‐joint position error of 0.078 m. This framework maintains high estimation stability even during destructive multipath fading, opening new avenues for intelligent electromagnetic surveillance and robust human‐machine interaction.

Optical computing holds significant promise across diverse applications due to its low latency, power efficiency, and multidimensional processing capabilities. However, current diffraction neural networks (DNNs) generally lack reconfigurability, limiting the scalability of the optical computing systems. Inspired by movable-type printing technology, here we propose a movable-type coding metasurface to enable multiple functionalities such as electromagnetic (EM) computing, holography, and sensing. By cascading multiple layers of the proposed metasurfaces, we further develop a movable-type reconfigurable DNN (MT-RDNN). It can be seamlessly adapted from handwritten digit to letter classification tasks by replacing the meta-atoms in the last hidden metasurface layer. Moreover, a single-layer movable-type coding metasurface can be reconfigured to perform EM holography and multi-person vital sign sensing through modular meta-atom rearrangement. Featuring simple reconfiguration, high flexibility, and modular scalability, the proposed movable-type coding metasurface enables versatile and reusable EM computing, holography, and sensing applications.

Previous studies on topological insulators have predominantly focused on the toroidal Brillouin zone (BZ) framework. In this work, we propose a novel octupole topological insulator in three-dimensional (3D) real projective space (RP3) and experimentally realize it via topological circuits, where corner-localized impedance peaks serve as signatures of the topological corer states. Our findings broadens the topological landscape and provide new insights into band theory within non-toroidal Brillouin manifolds.

Aberration-corrected focus scanning is crucial for high-precision optics, but the conventional optical systems rely on bulky and complicated dynamic correctors. Recently, Shiyi Xiao's group proposed a method using two rotating cascaded transmissive metasurfaces for adaptive aberration correction in focus scanning. The optimized phase profiles enable precise control of the focal position for scanning custom-curved surfaces. This concept was experimentally validated by two all-silicon meta-devices in the terahertz regime, paving the way for high-precision and compact optical devices in various applications.

This paper proposes a reconfigurable intelligent surface (RIS)-enhanced WiFi sensing system for respiration-based person identification (PID). By optimizing EM wave focusing, RIS improves respiration signal extraction, enabling accurate classification with a ResNet model. Experimental results achieve 92.5% PID accuracy, demonstrating the potential of RIS for wireless biometric recognition in security and smart environments.

Polarization and phase manipulations have gained widespread applications across various fields. The emergence of metasurface provides a new platform for the manipulation of electromagnetic waves. However, most metasurfaces are limited to modulating only one single property. Here, a coding metasurface that achieves 1-bit phase manipulations of both co-polarized and cross-polarized reflected waves for linear and circular polarization wave excitations. Notably, the proposed metasurface enables co-polarized 1-bit phase responses for incident electric fields with arbitrary orientations and spin directions. The simulated results demonstrate an operating efficiency over -1.7 dB in the frequency range from 7 to 11.1 GHz, with a relative bandwidth of 45.3%. Furthermore, the introduction of space-polarization coding strategies facilitates the beam and polarization manipulations. To verify the feasibility of the coding metasurface, a sample and conduct experiments are fabricated, revealing good agreement between the simulations and measurements. These findings hold significant promise for the advancement of radar, imaging, and wireless communication systems, with potential applications in various domains. Under excitations of linear and circular polarization waves, the proposed coding metasurface achieves 1-bit phase manipulation of both co-polarized and cross-polarized reflection waves. Additionally, the co-polarized phase manipulation is polarization insensitive, allowing for incident waves with electric fields of arbitrary orientation and spin direction. Simulation results demonstrate an efficiency above -1.7 dB from 7 to 11.1 GHz. image

Reflective Moire metasurface provides an economical approach for dynamic beamforming in RIS applications, introducing novel methods for far-field scattering synthesis through compact, ultrathin metallic patterns with diverse symmetries. This breakthrough is expected to have widespread impact across the fields of electromagnetics, antenna development, and wireless communication.

Space-time-coding (STC) digital metasurfaces provide a powerful platform for simultaneous spatiotemporal modulations of electromagnetic waves. Therefore, the fast and accurate generation of STC matrices based on desired harmonic scattering patterns can help STC metasurfaces enhance their practicality in various applications. Here, we propose a physics-driven vector-quantized (PD-VQ) intelligent autoencoder model that consists of an encoder, a vector-quantizer layer, and a physics-driven decoder. The physical operation mechanism between the STC matrix and the harmonic scattering pattern is introduced into the decoding module of the PD-VQ intelligent autoencoder, so that the autoencoder can be trained in an unsupervised manner without the need for large amount of manually labeled data. Taking a target harmonic scattering pattern as input, the trained PD-VQ autoencoder can quickly output the optimized discrete STC matrix, which takes only about 78 ms. We present a series of simulation examples to verify the reliability and accuracy of the proposed approach and also demonstrate its good generalization capability. Based on the proposed PD-VQ intelligent autoencoder, the STC digital metasurfaces enable agile multi-frequency harmonic beamforming.

To address the gain loss issue of non-regularly arranged circularly polarized array antennas, this paper proposes a feeding method that compensates for the installation angle of the array elements by adjusting the feeding phase based on the electric field intensity synthesis of circularly polarized array antennas. The correctness of the theoretical analysis is verified through the simulation of a three-element array calculated using commercial software. This feeding method can be generalized to other non-regularly arranged circularly polarized arrays with arbitrary forms.

Gas-phase synthesized binary nanoparticles (NPs) possess ultraclean surfaces, which benefit versatile uses in sensors and catalysts. However, precise control of their configuration and properties is still a big challenge because the growth mechanism and phase evolution dynamics in these NPs are very hard to unveil. Here, we report a strategy to investigate the phase evolution dynamics in binary NPs by using e-beam assisted ultrafast local heating and cooling inside a transmission electron microscope. With this strategy, the phase segregation and corresponding shape evolution of PbBi NPs are in situ revealed. It is found that the as-prepared PbBi alloy NPs will transform into heterostructures under e-beam stimulated structural relaxation, leading to the formation of featured Janus configurations with faceted Bi polyhedron parts and intermetallic hemisphere parts. During phase segregation, Pb1Bi1 and Pb7Bi3 phases are captured and identified, and a model of phase and shape evolution of PbBi nanoalloys is developed and contrasted with that of their bulk counterparts. These findings benefit the understanding of the phase dynamics of binary NPs and can provide in-depth information for engineering their structures for practical applications.

The polarizations of electromagnetic (EM) waves are very important for transceivers. We propose a broadband polarization-insensitive polarization rotator (PIPR), which can realize 90° polarization rotation for incident waves with an arbitrary azimuth angle. A unit of the PIPR is composed of two types of substrate integrated waveguide (SIW) units in a checkerboard pattern, which provides more than -0.2 dB transmission from 9.5 to 10.9 GHz. The electric field inside the cavity is analyzed to explain the working mechanism of the proposed rotator. A prototype is fabricated and measured to verify the proposed design, and satisfactory agreement between simulated and measured results is achieved, indicating that the converter has potential applications in imaging and communication systems.

Room-temperature exciton-polariton Bose-Einstein condensation (BEC), a phase transition to single quantum state with strong nonlinearity, provides a new strategy for coherent light sources and ultralow threshold optic switches. In this work, colloidal CdSe/CdS 2D nanoplatelets are embedded into a microcavity, and exciton-polariton BEC is realized with an ultralow threshold of 0.5 µJ cm-2 at room temperature. The superlinear power-dependent emission, macroscopic occupation of the ground state, strong blueshift and broadening of the emission peak, and long-range coherence strongly confirm the realization of the polariton laser. This work suggests considerable prospects for colloidal nanoplatelets in low-cost, high-performance polariton devices, and coherent light sources.

Reconfigurable intelligent surfaces (RISs) offer an entirely new route to alter the propagation properties of electromagnetic waves and thus control their reflection, refraction, and scattering features in arbitrary manners. Such physical attributes are perceived to bring about fundamental influence on the modern wireless communication system due to the possibilities to establish artificial and controllable propagation environments for radio signals, which no longer rely on the complex encoding, decoding, and other signal processing techniques. Recent studies reveal that the wave manipulation is not the only skill of the RISs. With the rapid developments of space–time digital metasurface and information metasurface, there has been increasing attention focused on the information manipulation via these artificial surfaces. In this article, we provide an overview of the theoretical models of the space–time digital metasurface and information metasurface, the mechanisms of wavefront shaping, and the signal modulations in space and time domains during the wave–matter interactions. We will also address some practical issues during implementations of the reconfigurable intelligent metasurfaces and the associated hardware architectures at microwave frequencies to realize simplified radio frequency transmitters. Several modulation schemes and the corresponding demonstration systems are introduced to illustrate the powerful abilities of the reconfigurable intelligent metasurfaces. Potential research directions of this technique are briefly discussed for their potential applications in future wireless networks.

A dual-band, high polarization conversion ratio (PCR) tunable flexible polarization conversion metasurface based on the reversible insulator-to-metal transition (IMT) of vanadium dioxide (VO2) is proposed. It consists of a pattern layer combining VO2 and copper, two flexible dielectric layers and a metallic ground. The simulation results show that the proposed metasurface can achieve linear polarization conversion in 8.17-12.87 GHz and 14.63-18.92 GHz in the insulting phase. And the PCRs of the two band are 97.06% and 98.13%, the corresponding relative bandwidths are 44.68% and 25.58%, respectively. In the metallic phase, the PCRs within 6.81-13.95GHz and 16.23-18.16 GHz are 91.12% and 96.92%, respectively. The dynamic regulation characteristics of PCR and operating bandwidth are realized by changing the conductivity of VO2. The surface current at the resonant frequency is simulated, and the mechanisms of dual-band and high PCR are analyzed. In addition, the polarization converter exhibits good robustness when the x- and y-polarized incident angle is up to 30°. The proposed metasurface has great potential applications in antenna radiation, biosensing and stealth technology.

As one of the most important narrow bandgap ternary semiconductors, GaAs1−xSbx nanowires (NWs) have attracted extensive attention recently, due to the superior hole mobility and the tunable bandgap, which covers the whole near-infrared (NIR) region, for technological applications in next-generation high-performance electronics and NIR photodetection. However, it is still a challenge to the synthesis of high-quality GaAs1−xSbx NWs across the entire range of composition, resulting in the lack of correlation investigation among stoichiometry, microstructure, electronics, and NIR photodetection. Here, we demonstrate the success growth of high-quality GaAs1−xSbx NWs with full composition range by adopting a simple and low-cost surfactant-assisted solid source chemical vapor deposition method. All of the as-prepared NWs are uniform, smooth, and straight, without any phase segregation in all stoichiometric compositions. The lattice constants of each NW composition have been well correlated with the chemical stoichiometry and confirmed by high-resolution transmission electron microscopy, X-ray diffraction, and Raman spectrum. Moreover, with the increase of Sb concentration, the hole mobility of the as-fabricated field-effect-transistors and the responsivity and detectivity of the as-fabricated NIR photodetectors increase accordingly. All the results suggest a careful stoichiometric design is required for achieving optimal NW device performances.

Electromagnetic metasurfaces are structured surfaces consisting of a thin array of subwavelength elements with engineered scattering properties, thus providing a promising means of holographic display by controlling the field distributions. However, the existing metasurface holography has limited capabilities in achieving 3-D fields with simultaneous features of high spatial resolution and energy efficiency due to the design methods. In this work, we present a transmissive metasurface to achieve polarization-dependent field distributions in 3-D space with both high resolution and efficiency. In the design, a new method that utilizes dyadic Green's function (DGF) as the rigorous propagator is used. Using the method, the sources and fields are linked directly and can be located on arbitrary 3-D points with the intermediate spaces being equal or unequal. The design is successfully validated by full-wave simulations and experimental measurements. The broadband simulation results indicate that the design has a bandwidth of 0.8 GHz. This work demonstrates a feasible and simple route of field synthesis for real-world applications that require high resolution, high efficiency, and 3-D scenarios.

In the past decades, defect engineering has become an effective strategy to significantly improve the hydrogen evolution reaction (HER) efficiency of electrocatalysts. In this work, a facile chemical vapor deposition (CVD) method is firstly adopted to demonstrate defect engineering in high-efficiency HER electrocatalysts of vanadium diselenide nanostructures. For practical applications, the conductive substrate of carbon cloth (CC) is selected as the growth substrate. By using a four-time CVD method, uniform three-dimensional microflowers with defect-rich small nanosheets on the surface are prepared directly on the CC substrate, displaying a stable HER performance with a low Tafel slope value of 125 mV dec −1 and low overpotential voltage of 295 mV at a current density of 10 mA cm −2 in alkaline electrolyte. Based on the results of x-ray photoelectron spectra and density functional theory calculations, the impressive HER performance originates from the Se vacancy-related active sites of small nanosheets, while the microflower/nanosheet homoepitaxy structure facilitates the carrier flow between the active sites and conductive substrate. All the results present a new route to achieve defect engineering using the facile CVD technique, and pave a novel way to prepare high-activity layered electrocatalysts directly on a conductive substrate.

Digital coding metasurfaces have attracted considerable interest, owing to their ability to manipulate electromagnetic waves and implement various functionalities with programmable controls. These metasurfaces offer high-resolution and high-speed responses; thus, they are implemented in high-speed imaging, nondestructive sensing, and wireless communication. However, traditional active metasurfaces are typically based on semiconductor components, which are difficult to realize at terahertz frequencies. Additionally, non-magnetic transmissive metasurfaces cannot realize a large phase-tuning range without increasing the number of metasurface layers. Herein, a 1-bit transmissive digital coding metasurface based on liquid crystals is proposed to achieve programmable terahertz beam manipulations with electric control. The Fano resonance that is excited in the asymmetrical metasurface element enables a larger phase variation while maintaining the transmittance. The proposed digital metasurface can effectively achieve many functionalities, such as dual beam steering, multiple beams, and orbital angular momentum beams, via altered coding patterns; an example of dual beam steering is experimentally verified. This study is expected to provide a promising method to manipulate transmissive terahertz beams using a digitally programmable metasurface, and it has potential applications in imaging, sensing, and wireless communications.

For one-dimensional (1D) topological insulators, the edge states always reside in the bulk bandgaps as isolated modes. The emergence and vanishing of these topological edge states are always associated with the closing/reopening of the bulk bandgap and changes in topological invariants. In this work, we discover a special kind of edge state in a 1D electrical circuit, which can appear not only inside the bandgap but also outside the bulk bands with the changing of bulk circuit parameters, resembling Tamm states or Shockley states. We prove analytically that the emergence/vanishing of this edge state and its position relative to the bulk bands depends on the intersections of certain critical frequencies. Specifically, the edge mode in the proposed circuit can be mathematically described by polynomials with roots equal to some critical frequencies in the bulk circuit. From this point of view, the transition of the edge state is uniquely determined by the order of the critical frequencies in the bulk circuit. Such topological behaviors shown by the edge state in the proposed electrical circuit may indicate, in a broader sense, the presence of certain type of topology.

Beam-induced heating effect on nanoscale samples is a crucial question as it strongly influences the interpretation of observed unusual behaviors. This question is currently under debate without a convincing conclusion. Here, using silver nitride (Ag 3 N) nanoparticles as temperature labels, we perform an investigation on this heating effect inside a transmission electron microscope (TEM) under normal imaging conditions. Combined with experimental measurements and semi-quantitative calculations, a temperature increase of more than 100 K is estimated and confirmed in the graphite carbon nitride (g-C 3 N 4 ) films. Strong temperature gradients are found to exist in the single-end fixed g-C 3 N 4 films. The influencing factors of heat accumulation are also investigated and discussed. Findings in this paper may shed some light on the understanding of the abnormal behaviors of nano-objects observed inside TEM.