The outbreak of COVID-19 caused by SARS-CoV-2 has resulted in more than 50 million confirmed cases and over 1 million deaths worldwide as of November 2020. Currently, there are no effective ...antivirals approved by the Food and Drug Administration to contain this pandemic except the antiviral agent remdesivir. In addition, the trimeric spike protein on the viral surface is highly glycosylated and almost 200,000 variants with mutations at more than 1,000 positions in its 1,273 amino acid sequence were reported, posing a major challenge in the development of antibodies and vaccines. It is therefore urgently needed to have alternative and timely treatments for the disease. In this study, we used a cell-based infection assay to screen more than 3,000 agents used in humans and animals, including 2,855 small molecules and 190 traditional herbal medicines, and identified 15 active small molecules in concentrations ranging from 0.1 nM to 50 μM. Two enzymatic assays, along with molecular modeling, were then developed to confirm those targeting the virus 3CL protease and the RNA-dependent RNA polymerase. Several water extracts of herbal medicines were active in the cell-based assay and could be further developed as plant-derived anti-SARS-CoV-2 agents. Some of the active compounds identified in the screen were further tested in vivo, and it was found that mefloquine, nelfinavir, and extracts of
(RF3),
, and
were effective in a challenge study using hamsters as disease model.
Vector vortex beams (VVBs) possess ubiquitous applications from particle trapping to quantum information. Recently, the bulky optical devices for generating VVBs have been miniaturized by using ...metasurfaces. Nevertheless, it is quite challenging for the metasurface‐generated VVBs to possess arbitrary polarization and phase distributions. More critical is that the VVBs' annular intensity profiles demonstrated hitherto are dependent on topological charges and are hence not perfect, posing difficulties in spatially shared co‐propagation of multiple vortex beams. Here, a single‐layer metasurface to address all those aforementioned challenges in one go is proposed, which consists of two identical crystal‐silicon nanoblocks with varying positions and rotation angles (i.e., four geometric parameters throughout). Those four geometric parameters are found to be adequate for independent and arbitrary control of the amplitude, phase, and polarization of light. Perfect VVBs with arbitrary polarization and phase distributions are successfully generated, and the constant intensity profiles independent of their topological charges and polarization orders are demonstrated. The proposed strategy casts a distinct perception that a minimalist design of just one single‐layer metasurface can empower such robust and versatile control of VVBs. That provides promising opportunities for generating more complex vortex field for advanced applications in structural light, optical micromanipulation, and data communication.
A single‐layer dielectric metasurface, consisting of two crystal‐silicon nanoblocks within one unit, is proposed to control the amplitude, phase, and polarization of light independently and arbitrarily. A genetic algorithm is used to obtain the geometric parameters of the metasurface element. The proposed strategy enables perfect vector vortex beam generation with constant annular intensity profiles, arbitrary phase, and polarization distributions.
The programmable one-pot oligosaccharide synthesis method was designed to enable the rapid synthesis of a large number of oligosaccharides, using the software Optimer to search Building BLocks (BBLs) ...with defined relative reactivity values (RRVs) to be used sequentially in the one-pot reaction. However, there were only about 50 BBLs with measured RRVs in the original library and the method could only synthesize small oligosaccharides due to the RRV ordering requirement. Here, we increase the library to include 154 validated BBLs and more than 50,000 virtual BBLs with predicted RRVs by machine learning. We also develop the software Auto-CHO to accommodate more data handling and support hierarchical one-pot synthesis using fragments as BBLs generated by the one-pot synthesis. This advanced programmable one-pot method provides potential synthetic solutions for complex glycans with four successful examples demonstrated in this work.
Thermal camouflage has been successful in the conductive regime, where thermal metamaterials embedded in a conductive system can manipulate heat conduction inside the bulk. Most reported approaches ...are background-dependent and not applicable to radiative heat emitted from the surface of the system. A coating with engineered emissivity is one option for radiative camouflage, but only when the background has uniform temperature. Here, we propose a strategy for radiative camouflage of external objects on a given background using a structured thermal surface. The device is non-invasive and restores arbitrary background temperature distributions on its top. For many practical candidates of the background material with similar emissivity as the device, the object can thereby be radiatively concealed without a priori knowledge of the host conductivity and temperature. We expect this strategy to meet the demands of anti-detection and thermal radiation manipulation in complex unknown environments and to inspire developments in phononic and photonic thermotronics.
Metasurfaces are used to enable acoustic orbital angular momentum (a‐OAM)‐based multiplexing in real‐time, postprocess‐free, and sensor‐scanning‐free fashions to improve the bandwidth of acoustic ...communication, with intrinsic compatibility and expandability to cooperate with other multiplexing schemes. The metasurface‐based communication relying on encoding information onto twisted beams is numerically and experimentally demonstrated by realizing real‐time picture transfer, which differs from existing static data transfer by encoding data onto OAM states. With the advantages of real‐time transmission, passive and instantaneous data decoding, vanishingly low loss, compact size, and high transmitting accuracy, the study of a‐OAM‐based information transfer with metasurfaces offers new route to boost the capacity of acoustic communication and great potential to profoundly advance relevant fields.
Acoustic communication is pivotal in applications such as ocean exploration, while its bandwidth is hitting the ceiling. Twisted acoustics for real‐time information transfer is theoretically proposed and experimentally demonstrated in a passive, postprocess‐free, and sensor scanning‐free fashion with metasurfaces and a single transducer. The study helps to boost the capacity of acoustic communication and advance relevant fields.
Metasurfaces have enabled a plethora of emerging functions within an ultrathin dimension, paving way towards flat and highly integrated photonic devices. Despite the rapid progress in this area, ...simultaneous realization of reconfigurability, high efficiency, and full control over the phase and amplitude of scattered light is posing a great challenge. Here, we try to tackle this challenge by introducing the concept of a reprogrammable hologram based on 1-bit coding metasurfaces. The state of each unit cell of the coding metasurface can be switched between '1' and '0' by electrically controlling the loaded diodes. Our proof-of-concept experiments show that multiple desired holographic images can be realized in real time with only a single coding metasurface. The proposed reprogrammable hologram may be a key in enabling future intelligent devices with reconfigurable and programmable functionalities that may lead to advances in a variety of applications such as microscopy, display, security, data storage, and information processing.Realizing metasurfaces with reconfigurability, high efficiency, and control over phase and amplitude is a challenge. Here, Li et al. introduce a reprogrammable hologram based on a 1-bit coding metasurface, where the state of each unit cell of the coding metasurface can be switched electrically.
Artificially structured thermal metamaterials provide an unprecedented possibility of molding heat flow that is drastically distinct from the conventional heat diffusion in naturally conductive ...materials. The Laplacian nature of heat conduction makes the transformation thermotics, as a design principle for thermal metadevices, compatible with transformation optics. Various functional thermal devices, such as thermal cloaks, concentrators, and rotators, have been successfully demonstrated. How far can it possible go beyond just realizing a heat‐distribution function in a thermal metadevice? Herein, the concept of encrypted thermal printing is proposed and experimentally validated, which could conceal encrypted information under natural light and present static or dynamic messages in an infrared image. Regionalization transformation is developed for structuring thermal metamaterial‐strokes as infrared signatures, enabling letters of the alphabet to be written, paintings to be drawn, movies to be made, and information to be displayed. This strategy successfully demonstrates an extreme level of manipulation of heat flow for encryption, illusions, and messaging.
Heat conduction has long been considered in an omnidirectional diffusive way. Such a stereotype is successfully broken in this work and extreme heat flow manipulation is achieved, based on which encrypted thermal printing and regionalization transformation for structuring thermal metamaterial‐strokes as infrared signatures are proposed, enabling the writing of letters, the drawing of paintings, and the display of information.
Bulk photovoltaic effect (BPVE), featuring polarization-dependent uniform photoresponse at zero external bias, holds potential for exceeding the Shockley-Queisser limit in the efficiency of existing ...opto-electronic devices. However, the implementation of BPVE has been limited to the naturally existing materials with broken inversion symmetry, such as ferroelectrics, which suffer low efficiencies. Here, we propose metasurface-mediated graphene photodetectors with cascaded polarization-sensitive photoresponse under uniform illumination, mimicking an artificial BPVE. With the assistance of non-centrosymmetric metallic nanoantennas, the hot photocarriers in graphene gain a momentum upon their excitation and form a shift current which is nonlocal and directional. Thereafter, we demonstrate zero-bias uncooled mid-infrared photodetectors with three orders higher responsivity than conventional BPVE and a noise equivalent power of 0.12 nW Hz
. Besides, we observe a vectorial photoresponse which allows us to detect the polarization angle of incident light with a single device. Our strategy opens up alternative possibilities for scalable, low-cost, multifunctional infrared photodetectors.
Janus monolayers, a class of two‐faced 2D materials, have received significant attention in electronics, due to their unusual conduction properties stemming from their inherent out‐of‐plane ...asymmetry. Their photonic counterparts recently allowed for the control of hydrogenation/dehydrogenation processes, yielding drastically different responses for opposite light excitation spins. A passive Janus metasurface composed of cascaded subwavelength anisotropic impedance sheets is demonstrated. By introducing a rotational twist in their geometry, asymmetric transmission with the desired phase function is realized. Their broken out‐of‐plane symmetry realizes different functions for opposite propagation directions, enabling direction‐dependent versatile functionalities. A series of passive Janus metasurfaces that enable functionalities including one‐way anomalous refraction, one‐way focusing, asymmetric focusing, and direction‐controlled holograms are experimentally demonstrated.
Direction‐encoded wave manipulations are experimentally achieved through the use of Janus metasurfaces composed of cascaded metasheets. By introducing a rotational twist in metasurface geometry, asymmetric electromagnetic wavefront manipulation can be realized. This is demonstrated both theoretically and experimentally by a series of passive metadevices, which enable functionalities including one‐way anomalous refraction, one‐way focusing, asymmetric focusing, and direction‐controlled holograms.
PDF
