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Spoof plasmonics, which can enable strong terahertz (THz) radiation–matter interactions, hold great promise for the advancement of THz science and technology. However, THz spoof plasmonic devices based on micro-structured metals are in general limited by lithography-based fabrication processes as well as metals' mechanical, chemical, and thermal stability, which hinders their applications in, for instance, flexible and wearable THz imaging and communications, molecular sensing, etc. Possessing high electrical conductivity and outstanding mechanical robustness, graphene-assembled films (GAFs) promise many benefits for electronics as an alternative to metals. Here, by studying the resonance-enhanced transmission properties of subwavelength GAF hole arrays, we demonstrate a GAF metasurface as a transformative platform for flexible THz spoof plasmonics. Based on a laser direct writing (LDW) patterning technique, the proposed micro-engineered GAF is expected to pave the way toward large-area, durable, and inexpensive THz metadevices with superior flexibility. [ABSTRACT FROM AUTHOR]

In this paper, the Cr films with preferred orientation evolution from (110) to (200) were deposited on the surface of austenitic stainless steel. These films were driven by a pulsed bias with different duty cycles from 20% to 80%, followed by a postnitriding process for 1 h using a hot wire plasma-enhanced magnetron sputtering system. XRD result showed Cr film had a body-centered cubic lattice structure, and the orientation transformed from (110) to (200) with the increase in the duty cycle. SEM and EDS measurements revealed that Cr film structured with columnar crystals could contribute to the continuous diffusion of nitrogen into austenite lattice. N atoms tended to diffuse along the (200) orientation of Cr films than the close-packed (110) orientation. As a result, the best wear resistance and adhesion strength were obtained when Cr film deposited at 80% duty cycle was nitrided, and the wear volume decreased by 95.7% compared with that before nitriding. [ABSTRACT FROM AUTHOR]

Ultrathin and two-dimensional (2D) metals can support strong plasmons, with concomitant tight field confinement and large field enhancement. Accordingly, 2D-metal nanostructures exhibiting plasmonic resonances are highly sensitive to the environment and intrinsically suitable for optical sensing. Here, based on a proof-of-concept numerical study, nano-engineered ultrathin 2D-metal films that support infrared plasmons are demonstrated to enable highly responsive refractive index (RI) sensing. For 3 nm-Au nanoribbons exhibiting plasmonic resonances at wavelengths around 1600 nm, a RI sensitivity of SRI > 650 nm per refractive index unit (RIU) is observed for a 100 nm-thick analyte layer. A parametric study of the 2D-Au system indicates the strong dependence of the RI sensitivity on the 2D-metal thickness. Furthermore, for an analyte layer as thin as 1 nm, a RI sensitivity up to 110 (90 nm/RIU) is observed in atomically thin 2D-In (2D-Ga) nanoribbons exhibiting highly localized plasmonic resonances at mid-infrared wavelengths. Our results not only reveal the extraordinary sensing characteristics of 2D-metal systems but also provide insight into the development of 2D-metal-based plasmonic devices for enhanced IR detection. [ABSTRACT FROM AUTHOR]

Histopathology has remained the gold standard for surgical margin assessment for decades. However, routine pathological examination based on formalin-fixed and paraffin-embedded (FFPE) tissues is laborious and time-consuming, failing to guide surgeons intraoperatively. Here, we propose a rapid, label-free, and non-destructive histological imaging method, termed microscopy with ultraviolet single-plane illumination (MUSI). With intrinsic fluorescence from deep ultraviolet excitation, MUSI enables both ex vivo and in vivo imaging of fresh and unprocessed tissues at the subcellular level with an imaging speed of 0.5 mm2/s, generating high-quality optically sectioned surface images from irregular surgical tissues with a long depth-of-field. We demonstrate that MUSI could differentiate between different subtypes of human lung adenocarcinomas (e.g., lepidic, acinar, papillary, and micropapillary), revealing diagnostically important features that are comparable to the gold standard FFPE histology. As an assistive imaging platform, MUSI can provide immediate feedback to surgeons and pathologists for intraoperative decision-making, holding great promise to revolutionize the current clinical practice in surgical pathology. [ABSTRACT FROM AUTHOR]

The resonant nature and geometric scalability make metamaterials an ideal platform for an enhanced light–matter interaction over a broad frequency range. The mid-infrared (IR) spectral range is of great importance for vibrational spectroscopy of molecules, while IR metamaterials created from lithography-based planar nanostructures have been used to demonstrate enhanced molecular detection. Compared with visible and near-infrared, the relative long wavelengths of IR light make it possible to achieve three-dimensional (3D) IR metamaterials via the state-of-the-art 3D fabrication techniques. Here, we design and fabricate a 3D printed plasmonic metamaterial absorber (MMA), and by performing Fourier-transform IR spectroscopy, we demonstrate that a series of molecular fingerprint vibrations of glycine can be significantly enhanced by the high absorption mode supported by the 3D meta-atoms of the MMA. The observed enhanced IR detection can also be partially attributed to the improved accessibility offered by the 3D architecture of the MMA. In particular, due to capillary forces during the drying process, the microscale 3D printed features lead to selective analyte deposition in high-field regions, which provides another degree of freedom in the design of the 3D printed structures for surface-enhanced IR detection. Our study shows the flexibility of metastructures based on advanced 3D printing technology in tailoring the interaction between IR light and materials on a subwavelength scale. [ABSTRACT FROM AUTHOR]