chiral plasmonic nanoparticles and their self-assembled structures as colloidal suspensions. [6][7][8][9] Recently, beyond noble metal plasmonics, solid-state layered nanomaterials that are rotationally aligned with a defined twist angle are becoming increasingly investigated (Figure 1). Among these are twisted 2D van der Waals (vdW) materials, [10][11][12] twisted single-crystal slabs, [13,14] twisted aligned nanowire thin films, [15][16][17][18] and twisted metasurfaces with periodic subunits [19][20][21] (Figure 2). These chiral stacked materials possessing geometric handedness and optical chirality can be seen as truncated and minimalistic versions of supramolecular liquid crystals in the chiral nematic phase or of 3D chiral photonic crystals. [22][23][24] Compared to their bulk or multiple-layer counterparts, the fabrication becomes greatly simplified for bilayer or few-layer chiral metamaterials, enabling precise control over the interlayer twist angle to manipulate lightmatter interactions. Ultrathin chiral metamaterials and metasurfaces with tunable optical and chiroptical responses are thus an active field for study.Twisting achiral layered nanostructures in parallel planes enables engineering of the extrinsic chirality and related optical performance. Specifically, the twist angle from counterclockwise rotation of an upper layer with respect to the beneath one is defined to be positive, θ > 0°, leading to a left-handed stacking geometry. [10,18] Accordingly, negative twist angle from clockwise rotation gives rise to the right-handed counterpart. Accurate control over the interlayer rotation angle offers flexible manipulation of properties, especially optical activity, of twisted layered systems of a wide variety of monolayer constituents and dimensions. A well-studied system is twisted bilayer graphene (TBG), catalyzing the research on twisted stacked nanostructures over the past few years, especially as many intriguing properties of magic-angle graphene are uncovered. [28][29][30] The twist angle dependencies of phonon dispersion, [31] optical absorption and reflection, [32,33] circular dichroism (CD) and birefringence, [10,34] second harmonic generation (SHG), [35] and photoresponse [36,37] of TBG have been extensively explored in the past few years. Similar realizations have been reported for twisted nanostructures of other 2D materials such as transition metal dichalcogenides, [38,39] graphitic carbon nitride, [40] and hexagonal boron nitride (hBN), [41] as well as non-2D systems like polymeric thin films or patterned plasmonic nanohole arrays. [42,43] Therefore, there exists fertile ground for chiral metasurface design Artificial chiral nanostructures have been subjected to extensive research for their unique chiroptical activities. Planarized chiral films of ultrathin thicknesses are in particular demand for easy on-chip integration and improved energy efficiency as polarization-sensitive metadevices. Recently, controlled twisted stacking of two or more layers of nanomaterials, such as 2D van der ...

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Ultrathin optical components with giant circular dichroism hold great promise for polarization‐sensitive nanophotonics. However, existing chiral metamaterials often rely on complex‐shaped nanoinclusions, and there remains a paucity of designs active in the shortwave infrared (SWIR) useful for telecommunication and night vision. Here a detailed numerical analysis of the chiroptical response of a simple twisted stacked variant of gap‐plasmon metasurface is presented based on periodic nanohole arrays. Impressively, the 100‐nm free‐standing plasmonic metasurface can attain a thickness‐normalized ellipticity of up to 74.2° µm−1 with tunable bands in the SWIR. Strong and robust optical activity is achieved through energy confinement by gap surface plasmons and effective inter‐nanohole coupling, resulting in an intense superchiral near field. The ultrathin plasmonic metasurface serves as an excellent platform for refractive index sensing with a sensitivity Sn of up to 648.1 nm RIU−1 and field‐enhanced enantiodiscrimination. The simple metasurface with strong SWIR chirality can enjoy a multitude of potential applications including polarization‐sensitive photodetection, optical telecommunication, machine vision, medical imaging, and spectroscopy. These findings also offer insights into some fundamental design principles for twisted stacked aperture‐based metasurfaces and should facilitate the development of new chiral metamaterials with exceptional performance.

Carbon-based composite conductive ink (3CI) has some challenges to its properties. Here, combined with the application of 3CI on silicon keypads, a series of studies on the electrical, mechanical and thermal performance of 3CI has been conducted by adding specific concentrations of silver powder, silica powder and SiO2@Ag core-shell particles. The properties of the modified 3CI were characterized by using the four-point probe tester, scanning electron microscope, Rockwell hardness tester, cross-cut tester and laser thermal conductivity analyzer. The experimental results revealed that by adding silver powder with a particle size of 20 microns equivalent to 12% by weight of the 3CI, ink resistance decreased by 76%, from 8.44 kΩ/□ to 2.03 kΩ/□. Meanwhile, adding silica can increase the ink’s tensile strength and thermal diffusivity while improving the adhesion of the 3CI on the silicone rubber. It was worth noting that when the particle size of the SiO2@Ag core-shell particle was smaller than that of the added silver powder, the resistance of the 3CI was further reduced. Finally, a modified 3CI with the adhesion of 4B, a conductivity of about1 kΩ/□, a hardness of 232 HV0.5, and a thermal diffusivity of 0.217 cm2s−1 was achieved experimentally, which provided an experimental basis for the modified 3CI suitable for silicone keypads.