Complex-Amplitude Programmable Versatile Metasurface Platform Driven by Guided Wave.

Metasurfaces have shown unparalleled controllability of electromagnetic (EM) waves. However, most of the metasurfaces need external spatial feeding sources, which renders practical implementation quite challenging. Here, a low-profile programmable metasurface with 0.05λ0 thickness driven by guided waves is proposed to achieve dynamic control of both amplitude and phase simultaneously. The metasurface is fed by a guided wave traveling in a substrate-integrated waveguide, avoiding external spatial sources and complex power divider networks. By manipulating the state of the p-i-n diodes embedded in each meta-atom, the proposed metasurface enables 1-bit amplitude switching between radiating and nonradiating states, as well as a 1-bit phase switching between 0° and 180°. As a proof of concept, two advanced functionalities, namely, low sidelobe-level beam scanning and Airy beam generation, are experimentally demonstrated with a single platform operating in the far- and near-field respectively. Such complex-amplitude, programmable, and low-profile metasurfaces can overcome integration limitations of traditional metasurfaces, and open up new avenues for more accurate and advanced EM wave control within an unprecedented degree of freedom.

Low-cost laser cutting fabricated all-metallic metamaterial near-field focusing lens.

In this work, a low-cost all-metal metamaterial near-field lens based on laser cutting technology is proposed. A novel spiral-slot structure is proposed to achieve miniaturized unit cells with an adjustable 360-degree phase shift at a length smaller than 0.2 times the operating wavelength. Since the unit is entirely constructed of stainless steel, it is resistant to high temperatures and high pressures compared to existing results. Moreover, a four-layer structure is used to increase the transmission coefficient. The final L-band near-field lens is constructed of 20 × 20 units. Simulation and measured results show that the half-power beamwidth of the focus is less than 211 mm from 1.52 GHz to 1.68 GHz at the focal spot observation plane of 500 mm from the lens. Since numerically controlled machine tools and three-dimensional printing are prohibitively expensive for machining large metal components, a low-cost all-metallic lens was manufactured using laser cutting technology. The measured results are in agreement with the simulation results.

[Application of Various Methods to Extract Microplastic from Typical Soils in China].

Microplastics have been found in many environmental systems, such as oceans, terrestrial soils, sediments, and bodies of freshwater. Microplastic pollution in soils has received extensive international attention; however, there is currently no unified standard extraction method. To identify appropriate extraction and component identification methods for microplastics in typical soils in China, samples were identified and their polymer component properties examined using ATR-FTIR(Thermo Nicolet IS 20). The effects of three treatments of water+oil(T1), a saturated NaCl solution+oil(T2), and a saturated NaCl solution(T3) on the detection of four types of microplastics[polyethylene terephthalate(PET), polypropylene(PP), polystyrene(PS), and polyethylene(PE)]in four typical soils(loess, black soil, red soil, and purple soil) were examined. The results showed that:① The extraction rates of the T3 treatment decreased with microplastic density. For PP, PE, and PS, the extraction rates exceeded 86.67%, and the extraction rates of PET were 0%-13.30%. ② The extraction rates of the four kinds of microplastics were 86.67%-100.00% in loess, black soil, and purple soil using the T1 and T2 solutions; however, the residual oil on the surface of microplastics influenced the identification using FTIR. Furthermore, the cleaning effect of PE and PS was poor after wiping with anhydrous ethanol. ③ In red soil, the extraction rates of PET were 56.60% and 50.00% in T1 and T2, respectively; in the T3 treatment, the extraction rates of PET, PE, and PP were 3.33%, 10.00%, and 56.67%, respectively. These results show that the extraction rates of four types microplastics are highest for loess, black soil, and purple soil using T1 and T2, although these two methods need to be combined with anhydrous ethanol cleaning. T3 dispose making the leak of microplastics PET with the density higher than 1 g·cm-3. Methods to extract microplastics from red soils require further research. Overall, this study can inform the investigation and treatment of microplastic pollution in typical regional soils in China.