Responsive Liquid Crystal Network Microstructures with Customized Shapes and Predetermined Morphing for Adaptive Soft Micro-Optics.

Stimuli-responsive materials have garnered substantial interest in recent years, particularly liquid crystal networks (LCNs) with sophisticatedly designed structures and morphing capabilities. Extensive efforts have been devoted to LCN structural designs spanning from two-dimensional (2D) to three-dimensional (3D) configurations and their intricate morphing behaviors through designed alignment. However, achieving microscale structures and large-area preparation necessitates the development of novel techniques capable of facilely fabricating LCN microstructures with precise control over both overall shape and alignment, enabling a 3D-to-3D shape change. Herein, a simple and cost-effective in-cell soft lithography (ICSL) technique is proposed to create LCN microstructures with customized shapes and predesigned morphing. The ICSL technique involves two sequential steps: fabricating the desired microstructure as the template by using the photopolymerization-induced phase separation (PIPS) method and reproducing the LCN microstructures through templating. Meanwhile, surface anchoring is employed to design and achieve molecular alignment, accommodating different deformation modes. With the proposed ICSL technique, cylindrical and spherical microlens arrays (CMLAs and SMLAs) have been successfully fabricated with stimulus-driven polarization-dependent focusing effects. This technique offers distinct advantages including high customizability, large-area production, and cost-effectiveness, which pave a new avenue for extensive applications in different fields, exemplified by adaptive soft micro-optics and photonics.

Light-driven phase transition of diffractive optical elements based on liquid crystal elastomers.

Diffractive optical element is advantageous for miniaturization, arraying and integration of optical systems. They have been widely used in beam shaping, diffractive imaging, generating beam arrays, spectral optimization and other aspects. Currently, the vast majority of diffractive optics are not tunable. This limits the applicability and functionality of these devices. Here we report a tunable diffractive optical element controlled by light in the visible band. The diffractive optical element consists of a square gold microarray deposited on a deformable substrate. The substrate is made of a liquid crystal elastomer. When pumped by a 532 nm laser, the substrate is deformed to change the crystal lattice. This changes the far-field diffraction pattern of the device. The proposed concept establishes a light-controlled soft platform with great potential for tunable/reconfigurable photonic devices, such as filters, couplers, holograms and structural color displays.

Cholesteric liquid crystal-enabled electrically programmable metasurfaces for simultaneous near- and far-field displays.

Metasurfaces can enable polarization multiplexing of light so as to carry more information. Specific polarized light necessitates bulk polarizers and waveplates, which significantly increases the form size of metasurface devices. We propose an electrically programmable metasurface enabled by dual-frequency cholesteric liquid crystals (DF-CLCs) for simultaneous near- and far-field displays. Moreover, the integrated device can be electrically programmed to demonstrate 6 different optical images by engineering the DF-CLCs with frequency-modulated voltage pulses. Such programmable metasurfaces are potentially useful for many applications including information storage, displays, anti-counterfeiting, and so on.

Plasmonic Chiral Metasurface-Induced Upconverted Circularly Polarized Luminescence from Achiral Upconversion Nanoparticles.

Chirality induction, transfer, and manipulation have aroused great interest in achiral nanomaterials. Here, we demonstrate strong upconverted circularly polarized luminescence from achiral core-shell upconversion nanoparticles (UCNPs) via a plasmonic chiral metasurface-induced optical chirality transfer. The Yb3+-sensitized core-shell UCNPs with good dispersity exhibit intense upconversion luminescence of Tm3+ and Nd3+ through the energy transfer process. By spin-coating the core-shell UCNPs on this chiral metasurface, strong enhancement and circular polarization modulation of upconversion luminescence can be achieved due to resonant coupling between surface plasmons and upconversion nanoparticles. In the UCNPs-on-metasurface composite, a significant upconversion luminescence enhancement can be achieved with a maximum enhancement factor of 32.63 at 878 nm and an overall enhancement factor of 11.61. The luminescence dissymmetry factor of the induced upconverted circularly polarized luminescence can reach 0.95 at the emission wavelength of 895 nm. The UCNPs-on-metasurface composite yields efficient modulation for the emission intensity and polarization of UCNPs, paving new pathways to many potential applications in imaging, sensing, and anticounterfeiting fields.

Ultrathin Suspended Chiral Metasurfaces for Enantiodiscrimination.

Chiral metasurfaces can exhibit a strong circular dichroism, but it is limited by the complicated fabrication procedure and alignment errors. Here, a new type of self-aligned suspended chiral bilayer metasurface with only one-step electron beam lithography exposure is demonstrated. A significant optical chirality of 221° µm-1 can be realized using suspended metasurfaces with a thickness of 100 nm. Furthermore, this study experimentally demonstrates that such a structure is capable of label-free discrimination of the chiral molecules at zeptomole level, exhibiting a much higher sensitivity (orders of magnitude) compared to the conventional circular dichroism spectroscopy. The fundamental principles for chiral sensing using molecules-metasurfaces interactions are explored. Benefiting from the giant chiroptical response, the proposed metadevice may offer promising applications for ultrathin circular polarizers, chiral molecular detectors, and asymmetry information processing.

[Palmitic acid induces inflammation and transdifferentiation by activating cGAS/STING pathway in human renal tubular epithelial cells].

Objective To investigate the molecular mechanism of palmitic acid (PA) inducing inflammation and epithelial to mesenchymal transdifferentiation (EMT) in human renal tubular epithelial cells (RTECs). Methods The cell lipid accumulation model was prepared by RTECs and the cells were divided into blank control group, bovine serum albumin (BSA) group, PA group, and PA combined with stimulator of interferon genes (STING) specific inhibitor H151 group. The lipid accumulation of RTECs were detected by oil red O staining. Real-time quantitative PCR was used to detect the mRNA levels of interleukin 6 (IL-6), IL-8, transforming growth factor ß1 (TGF-ß1), and type 1 collagen alpha 1 chain (COL1A1) in RTECs. The protein expressions of STING, nuclear factor-κB p65 (NF-κB p65), phosphorylated NF-κB p65 (p-NF-κB p65), TGF-ß1, and type 1 collagen (Col1) were detected by Western blot and the expression and distribution of Col1 in RETCs were detected by immunofluorescence chemical staining. Results Compared with the control group, PA stimulated the lipid deposition, the expression of STING, and the phosphorylation of NF-κB p65 obviously, up-regulated the mRNA levels of IL-6, IL-8, TGF-ß1, and COL1A1 significantly, increased the protein expressions of TGF-ß1 and Col1 and the distribution of Col1 in RTECs; compared with those in the PA group, after H151 treatment, the expression of STING and the phosphorylation of NF-κB p65 decreased notably, the mRNA levels of IL-6, IL-8, TGF-ß1, and COL1A1 were down-regulated dramatically, and the protein expressions of TGF-ß1 and Col1 declined with reduced distribution of Col1. Conclusion PA induces lipid deposition, activated the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)/STING pathway, and caused inflammation and EMT in RTECs.

Photoelastic plasmonic metasurfaces with ultra-large near infrared spectral tuning.

Metasurfaces, consisting of artificially fabricated sub-wavelength meta-atoms with pre-designable electromagnetic properties, provide novel opportunities to a variety of applications such as light detectors/sensors, local field imaging and optical displays. Currently, the tuning of most metasurfaces requires redesigning and reproducing the entire structure, rendering them ineligible for post-fabrication shape-morphing or spectral reconfigurability. Here, we report a photoelastic metasurface with an all-optical and reversible resonance tuning in the near infrared range. The photoelastic metasurface consists of hexagonal gold nanoarrays deposited on a deformable substrate made of a liquid crystalline network. Upon photo-actuation, the substrate deforms, causing the lattice to change and, as a result, the plasmon resonance to shift. The centre wavelength of the plasmon resonance exhibits an ultra-large spectral tuning of over 245 nm, from 1490 to 1245 nm, while the anisotropic deformability also endows light-switchable sensitivity in probing polarization. The proposed concept establishes a light-controlled soft platform that is of great potential for tunable/reconfigurable photonic devices, such as nano-filters, -couplers, -holograms, and displays with structural colors.

Electrically Switchable, Polarization-Sensitive Encryption Based on Aluminum Nanoaperture Arrays Integrated with Polymer-Dispersed Liquid Crystals.

Metasurface-based structural coloration is a promising enabling technology for advanced optical encryption with a high-security level. Herein, we propose a paradigm of electrically switchable, polarization-sensitive optical encryption based on designed metasurfaces integrated with polymer-dispersed liquid crystals. The metasurfaces consist of anisotropic and isotropic aluminum nanoaperture arrays. Optical images can be encrypted by elaborately arranging anisotropic and isotropic nanoapertures based on their polarization-dependent plasmonic resonance characteristics. We demonstrate high-quality encrypted images and QR codes with electrically switchable, polarization-sensitive properties based on PDLC-integrated aluminum nanoaperture arrays. The proposed technique can be applied to many fields including high-security optical encryption, security tags, anticounterfeiting, multichannel imaging, and dynamic displays.

Vectorial holography-mediated growth of plasmonic metasurfaces.

Nowadays, the electromagnetic properties of artificial photonic materials can be well-tuned via designs over their composition and geometries. However, engineering the properties of artificial materials at the nanoscale is challenging and costly. Here we demonstrate a facile and low-cost method for fabricating large-area silver nanoparticle metasurfaces (AgNPMSs) by using the vectorial holography-mediated growth technique. The AgNPMS, which can be regarded as a hologram device, possesses excellent chiroptical properties. The vectorial holographic technique may open avenues for fabricating novel chiroptical metamaterials with large degrees of freedom, which can be further used for beam steering, photocatalysis, biosensing, etc.

A reprogrammable multifunctional chalcogenide guided-wave lens.

The transformation optics (TO) technique, which establishes an equivalence between a curved space and a spatial distribution of inhomogeneous constitutive parameters, has enabled an extraordinary paradigm for manipulating wave propagation. However, extreme constitutive parameters, as well as a static nature, inherently limit the simultaneous achievement of broadband performance, ultrafast reconfigurability and versatile reprogrammable functions. Here, we integrate the TO technique with an active phase-change chalcogenide to achieve a reconfigurable multi-mode guided-wave lens. The lens is made of a Rinehart-shaped curved waveguide with an effective refractive index gradient profile through partially crystallizing Ge2Sb2Te5. Upon changing the bias time of the external voltage imparted to the Ge2Sb2Te5 segments, the refractive index gradient profile can be tuned with a transformative platform for various functions for visible light. The electrically reprogrammable multi-mode guided-wave lens is capable of dynamically acquiring various functionalities with an ultrafast response time. Our findings may offer a significant step forward by providing a universal method to obtain ultrafast and highly versatile guided-wave manipulation, such as in Einstein rings, cloaking, Maxwell fish-eye lenses and Luneburg lenses.

Observation and Manipulation of Visible Edge Plasmons in Bi2Te3 Nanoplates.

Noble metals, like Ag and Au, are the most intensively studied plasmonic materials in the visible range. Plasmons in semiconductors, however, are usually believed to be in the infrared wavelength region due to the intrinsic low carrier concentrations. Herein, we observe the edge plasmon modes of Bi2Te3, a narrow-band gap semiconductor, in the visible spectral range using photoemission electron microscopy (PEEM). The Bi2Te3 nanoplates excited by 400 nm femtosecond laser pulses exhibit strong photoemission intensities along the edges, which follow a cos4 dependence on the polarization state of incident beam. Because of the phase retardation effect, plasmonic response along different edges can be selectively exited. The thickness-dependent photoemission intensities exclude the spin-orbit induced surface states as the origin of these plasmonic modes. Instead, we propose that the interband transition-induced nonequilibrium carriers might play a key role. Our results not only experimentally demonstrate the possibility of visible plasmons in semiconducting materials but also open up a new avenue for exploring the optical properties of topological insulator materials using PEEM.