Controlled Fabrication of 3D Chiral Microwrinkles via Asymmetrical and Biaxial Bucklings

Nano‐ and microsized chiral materials are receiving significant attention because of their unique characteristics, which include chiroptical activities and enantioselective interactions with living materials. However, the realization of chiral morphologies in such small‐scale materials has been an issue because of the complicated fabrication methods and limited material selection. In this study, a facile and reproducible method is developed for fabricating 3D chiral microwrinkles with twisted shapes by asymmetric and biaxial buckling. Soft polydimethylsiloxane (PDMS) substrates are asymmetrically stretched with angled biaxial strains and exposed to UV/ozone to prepare hard silica layers on top of the PDMS substrates to induce microwrinkles. The chiral shapes are controlled by changing the angle (θ) between the two strain axes and the UV/ozone exposure times (t₁, t₂) in each stage of buckling. The 3D chiral microwrinkles are shaped like “fusilli pasta” and occupy an area of 1.5 cm × 1.5 cm. The patterned area can be easily scaled, and no innate chiral biomaterial is necessary. This method could be widely extended to the fabrication of diverse types of chiral materials for advanced optical and bio‐applications.     

Plane Waves Propagating in Chiral Plasma and Chiral Ferrite Media

Plane wave propagation in chiral plasma and chiral ferrite media is studied in kDB coordinate system. General wave equations and characteristic equations of plane waves propagating along an arbitrary direction in chiral plasma and in chiral ferrites are derived in simple formulations respectively. Four wavenumbers and their corresponding dispersion characteristics are resulted for propagation both along and normal to the biasing magnetic field. When plane wave with negative helicity propagates along the biasing magnetic field in chiral ferrites, backward waves emerge. However backward waves occur with both positive and negative helicities when propagating along the biasing magnetic field in chiral plasma.     

Chiral 3D-printed Bioelectrodes

3D printing technology has gained great interest since it enables decentralized and customized manufacturing of 3D-printed electronic devices. From an electrochemical point of view, 3D-printed electrodes present promising achievements for (bio)sensing approaches. Herein, the feasibility of exploiting 3D-printed electrode substrates toward chiral analyses—a relevant topic owing to the homochiral nature of the biochemistry of life—has been interrogated for the first time. As a proof-of-concept, as-printed 3D-printed nanocomposite carbon electrodes (3D-nCEs) have been biofunctionalized with a model chiral selector like the class-enzyme L-amino acid oxidase for the ultrasensitive electrochemical discrimination of amino acid enantiomers. Interestingly, an unprecedented electrochemical approach has been devised, which relies on impedimetrically monitoring changes at the bioelectrode interface derived from the reactivity between the H₂O₂ by-product generated during enzymatic reactions and the 3D-nCE surface, yielding to the screening of amino acid enantiomers even at femtomolar concentrations. Different characterization techniques have been employed to elucidate the impedimetric mechanism involved for the electroanalysis. Accordingly, this work not only demonstrates the feasibility of exploiting 3D-printed electronic devices for enantiosensing achievements, but also brings out a general and straightforward electrochemical approach for the sensitive and selective analysis of enzymatic systems.     

Nanoimprint Meta-Device for Chiral Imaging

The polarization of light is a valuable information channel that has been studied extensively in optical devices. There has been limited progress in developing low-refractive index contrast and large-scale chiral meta-devices that are easy to integrate and mass-produce. In this image, a chiral imaging meta-device with a large area and broadband chirality control is experimentally demonstrated. The centimeter-scale Moiré meta-device is achieved using nanoimprint technology. The Poynting vector and singularity features in the near field and chiral optical response in the far field are discussed. The proposed Moiré meta-devices can achieve circular dichroism (CD) of more than 10%. Further chiral imaging harnessing CD mechanisms are demonstrated, which may lead to significant potential in various fields, including encryption and security, materials science, biochemistry, and medicine.     

Chiral Photodetector Based on GaAsN

The detection of light helicity is key for various applications, from drug production to optical communications. However, the light helicity direct measurement is inherently impossible with conventional photodetectors based on III–V or IV–VI non-chiral semiconductors. The prior polarization analysis by often moving optical elements is necessary before light is sent to the detector. A method is here presented to effectively give the conventional dilute nitride GaAs-based semiconductor epilayer a chiral photoconductivity. The detection scheme relies on the giant spin-dependent recombination of conduction electrons and the accompanying spin polarization of the engineered defects to control the conduction band. As the conduction electron spin polarization is, in turn, intimately linked to the excitation light polarization, the light polarization state and intensity can be determined by a simple conductivity measurement. This approach, removing the need for any optical elements in front of a non-chiral detector, could offer easier integration and miniaturization. This new chiral photodetector could potentially operate in a spectral range from the visible to the infra-red using (InGaAl)AsN alloys or ion-implanted nitrogen-free III–V compounds.     

A Thermoresponsive Membrane for Chiral Resolution

A novel thermoresponsive membrane for chiral resolution with high performance has been developed. The membrane exhibits chiral selectivity based on molecular recognition of beta‐cyclodextrin (β‐CD) and thermosensitivity based on the phase transition of poly(N‐isopropylacrylamide) (PNIPAM). Linear PNIPAM chains were grafted onto porous nylon‐6 membrane substrates by using a plasma‐graft pore‐filling polymerization method; the chains thus acted as microenvironmental adjustors for β‐CD molecules. β‐CD moieties were introduced into the linear PNIPAM chains by a chemical grafting polymerization method and acted as chiral selectors. The phase transition of grafted PNIPAM chains affects the microenvironment of β‐CD molecules and, thus, the association between β‐CD and guest molecules. The chiral selectivity of the prepared thermoresponsive membranes in chiral resolution operated at temperature below the lower critical solution temperature (LCST) of PNIPAM is higher than that of membranes with no thermosensitivity. Furthermore, the decomplexation ratio of enantiomer‐loaded thermoresponsive membranes in decomplexation at temperatures above the LCST is much higher than that of membranes with no thermosensitivity. Thus, by simply changing the operation temperature, high, selective chiral resolution and efficient membrane regeneration are achieved. The proposed membrane provides a new and efficient way to solve the difficult decomplexation problem of chiral solid membranes, which is highly attractive for chiral resolution.     

电磁波垂直入射到平面多层旋波煤质的反射

本文首先给出旋波煤质基本公式，然后从传输线理论出发，用阻抗法解决了线极化平面被垂直和入射到多层平面旋波媒质的反射向题，处理方法简单方便，且易理解。文中最后给出了一些数值模拟计算结果，并将其与另外的方法进行了比较．结果吻合得很好。     

Chiral Metallopolymers for Redox-Mediated Enantioselective Interactions

Synthetic chiral platforms can be a powerful platform for enantioselective interactions, especially when coupled with redox-mediated electrochemical processes. While metallopolymers are versatile platforms for molecularly selective binding, their application for chiral applications is limited. In particular, the recognition and separation of biologically relevant chiral molecules can be key for biomanufacturing and diagnostics. Here, the design of chiral redox-polymers enables electrochemically-controlled enantioselective interactions, and supramolecular chirality is leveraged for enhancing recognition towards target enantiomers. Chiral redox-metallopolymers are synthesized based on Ugi's amine-inspired chiral monomers, and their enantioselective recognition toward ionic enantiomers such as tryptophan and naproxen is demonstrated, with higher enanhcement provided by the chiral redox-polymer over the single-site, chiral building bloack itelf. 2D nuclear magnetic resonance spectroscopy and solid-state circular dichroism support the emergence of supramolecular chirality resulting from the intramolecular interaction between the ferrocene and the alkyl group in the backbone. The half potential shift of the redox-polymers behaves linearly from 0% to 100%ee l -tryptophan to enable enantiomer quantification. Investigation on solvent polarity and pH effect reveal that the enantioselective mechanism is attributed to the subtle balance between hydrogen bonding and π–π interaction. This study highlights the potential of chiral redox-metallopolymers as platforms for electrochemically-modulated enantioselective interactions towards a range of amino acids and pharmaceutical carboxylates.     

Enantioselective Crystallization on Chiral Polymeric Microspheres

In this article, a new approach to chiral resolution based on enantioselective crystallization on chiral polymeric microspheres is presented. To demonstrate the approach, a new synthetic method is developed for the preparation of porous and hollow chiral polymeric microspheres. Chiral microspheres based on poly(N‐vinyl α‐L ‐phenylalanine) (PV‐L ‐Phe) are synthesized from uniform polystyrene (PS) microsphere templates by a single‐step swelling process. The chiral microspheres display a narrow size distribution, and their properties, especially the porosity, can be controlled by varying the synthesis conditions. The chiral discrimination ability of these chiral microspheres is studied for D L ‐valine crystallization, as a model system for chiral racemic crystallization. X‐ray diffraction (XRD) and differential scanning calorimetry (DSC) provide evidence for the crystallization of enantiopure crystals on the chiral polymeric microspheres. Optical rotation measurements during crystallization show an enatiomeric excess of ca. 25 % for L ‐valine in the chiral microspheres. Although this excess is not yet very high, the basic principle of chiral discrimination by enantioselective crystallization on chiral microspheres is demonstrated.     

Circuit Representation of Isotropic Chiral Media

A four-port cascaded circuit model, which we call a chiral cascaded circuit, is presented to represent an isotropic and lossless chiral media. Such a model is based on the concept of transmission line and characteristic transformers. Detailed analysis is given to the chiral cascaded circuit and constitutive parameters for the effective chiral media are derived. Both the theoretical calculations for the effectively isotropic chiral media and circuit simulation results for the real chiral cascaded circuit are given, which have excellent agreements. Such a circuit model provides an efficient way to realize chiral media using transmission-line circuits and may find potential applications in microwave technologies.     

手征媒质反射特性仿真计算

手征媒质是双各向同性媒质的一种,其手征参数具有可调性。首先,在标准粒子群 算法(PSO)和模拟退火（SA）算法的基础上进行了改进,并利用混合算法优化设计手征参数 及媒质 厚度,以在给定的频率范围内获得较高的吸收率。然后,仿真计算了某一个参数取不同值而 其它参数固定情况下电磁波垂直入射到手征媒质时的反射系数。结果证明,只有在最优化参 数条件下才可以在频带内获得较理想的吸收率和反射系数。     

Recent Progress in Chiral Absorptive Metamaterials

Chiral metamaterial absorbers (CMMAs), a particular class of chiral metamaterials that refuse the transmission of incident radiation and exhibit different optical responses upon interactions with left and right circularly polarized (RCP) light, have gained research traction in recent years. CMMAs demonstrate numerous exotic and specialized applications owing to their achievable compatibility with various physical, chemical, and biomolecular systems. Aside from their well-evolved fabrication modalities for a broad range of frequencies, CMMAs exhibit strong chiroptical effects, making them central to various detection, imaging, and energy harvesting applications. Consequently, within the past decade, studies encompassing the design, optimization, and fabrication, as well as demonstrating the diverse applications of CMMAs have emerged. In this review, the theory, design, and fabrication of CMMAs are discussed, highlighting their top-down fabrication techniques as well as recent algorithmic and machine-learning (ML)-based approaches to the design and optimization. Some of their broad-spectrum applications are also discussed, spanning their roles in enantioselective photodetection, chiral imaging, generation of hot electrons, selective temperature sensing, and active chiral plasmonics.     

Analysis of Circular Chiral Dielectric Waveguides

The general eigenequations and the field expressions for circular waveguides containing chiral material in both the core and the cladding are given in a simple formulation. The results indicate that there are two types of field distribution which is related to the operating wavelength and chiral admittance. When the chiral admittance is larger than a critical value, the fields of one kind of circularly polarized wave in the core become exponentially-like damping in the transverse direction. Based on the eigenequations, the characteristics of a circular waveguide with chiral medium filled in the core are investigated. The relation between the cutoff frequency and the chiral admittance, the dispersion curves for some modes with different angular mode number and the transverse distribution of fields are presented. Some features different from the ordinary circular waveguide are resulted.     

Photopatterning Freestanding Chiral Nematic Mesoporous Organosilica Films

Chiral nematic mesoporous organosilica (CNMO) films are functionalized with a mixture of hydrophobic silanes and spiropyran compounds to create freestanding photochromic films that can be used for reversible photo­patterning. The mesoporosity and interconnected pore structure of the films imparted by the cellulose nanocrystal template enables a large cross‐section of the material to be functionalized. Thus, the materials show intense absorption spectra from the tethered spiropyran and rapid color changes when the porous films are irradiated with UV or white light. The spiropyran‐bound CNMO films behave as reversible sensors where metal binding to the spiropyran results in visible color changes detectable by the naked eye. These metals can be removed in the presence of ethanol and white light, regenerating the metal‐free film. The proof‐of‐concept demonstrated in this paper may help to develop new photochromic displays, security features, and patterns.     

Chiral Mechanical Metamaterials for Tunable Optical Transmittance

Flexible metamaterials have been increasingly harnessed to create functionality through their tunable and unconventional response. Herein, chiral unit cells based on Archimedean spirals are employed to transform a linear displacement into twisting. First, the effect of geometry on such extension-twisting coupling is investigated. This unravels a wide range of highly nonlinear behaviors that can be programmed. Additionally, it is demonstrated that by combining the spirals with polarizing films one can create mechanical pixels capable of modulating the transmission of light through deformation. Guided by experiments and numerical analyses, pixels are arranged in 2D arrays to realize black and white and color displays, which reveal distinct images at different states of deformation. As such, the study puts forward a methodology for the design of an emerging class of flexible devices that can convert nonlinear elastic deformation to tunable optical transmittance.     

Field-Effect Chiral Anomaly Devices with Dirac Semimetal

Charge-based field-effect transistors (FETs) greatly suffer from unavoidable carrier scattering and heat dissipation. Analogous to valley degree of freedom in semiconductors, chiral anomaly current in Weyl/Dirac semimetals is theoretically predicted to be nearly nondissipative over long distances, but still lacks experimental ways to efficiently control its transport. Here, field-effect chirality devices are demonstrated with Dirac semimetal PtSe₂, in which its Fermi level is close to the Dirac point in the conduction band owing to intrinsic defects. The chiral anomaly is further corroborated by the planar Hall effect and nonlocal valley transport measurement, which can also be effectively modulated by external fields, showing robust nonlocal valley transport with micrometer diffusion length. Similar to charge-based FETs, the chiral conductivity in PtSe₂ devices can be modulated by electrostatic gating with an ON/OFF ratio of more than 10³. Basic logic functions in the devices are also demonstrated with electric and magnetic fields as input signals.     

Induced Chiral Chromonics Confined in Micrometric Droplets

Chirality emergence in biological systems is common but the chiral expression from the molecular to macroscopic level in water-based systems is poorly understood. Among water-based systems, chromonic liquid crystals have recently received a lot of attention due to the spontaneous chirality they show when confined in curved geometries. Confinement of chiral-induced chromonics is not trivial since they are three component systems whose time stability is a delicate thermodynamic balance. In this work, a well-defined periodic Frank–Pryce texture, typical of chiral thermotropic liquid crystals, is observed in microspheres of a chiral induced chromonic embedded in a poly(dimethylsiloxane) matrix. This texture slowly degrades in time and a possible mechanism behind the degradation process is suggested via X-ray diffraction and atomic force microscopy measurements on thin chromonic films. To stabilize this texture and to control the structure periodicity, cations are added to the three components system in an attempt to tune the non-covalent interactions between molecules and supramolecular stacks. The study of the effects of this addition allows for better insight into the molecular interactions that occur in the chiral induced mesophase. This is a crucial point in view of possible biocompatible technological applications.