Topological defects in liquid crystal (LC) phases have been considered critical from the areas in topology and self‐assembly, as well as in applications such as optical vortex generation, particle manipulation system, and template for material micropatterning. An approach for generating and modulating various patterns of LC defects is presented in a single cell by varying the electrode configurations. Periodic LC defect arrays including −1 topological defect in the nematic phase can be achieved by simply adjusting crossed electrodes. Specifically, the fourfold symmetric −1 defect pattern is used as a vortex beam generator and a particle trapping agent with control either of the frequency of the applied electric field or the temperature. The approach suggested here would be beneficial to extend the use of LC patterns in lithographic tools and optoelectronic devices.
MicroRNAs (miRNAs) are emerging new biomarkers for many human diseases. To fully employ miRNAs as biomarkers for clinical diagnosis, it is most desirable to accurately determine the expression patterns of miRNAs. The optimum miRNA profiling method would feature 1) highest sensitivity with a wide dynamic range for accurate expression patterns, 2) supreme specificity to discriminate single nucleotide polymorphisms (SNPs), and 3) simple sensing processes to minimize measurement variation. Here, an ultra-specific detection method of miRNAs with zeptomole sensitivity is reported by applying bi-temperature hybridizations on single-crystalline plasmonic nanowire interstice (PNI) sensors. This method shows near-perfect accuracy of SNPs and a very low detection limit of 100 am (50 zeptomole) without any amplification or labeling steps. Furthermore, multiplex sensing capability and wide dynamic ranges (100 am-100 pm) of this method allows reliable observation of the expression patterns of miRNAs extracted from human tissues. The PNI sensor offers combination of ultra-specificity and zeptomole sensitivity while requiring two steps of hybridization between short oligonucleotides, which could present the best set of features for optimum miRNA sensing method.
Topological solitons have knotted continuous field configurations embedded in a uniform background, and occur in cosmology, biology, and electromagnetism. However, real‐time observation of their morphogenesis and dynamics is still challenging because their size and timescale are enormously large or tiny. Liquid crystal (LC) structures are promising candidates for a model‐system to study the morphogenesis of topological solitons, enabling direct visualization due to the proper size and timescale. Here, a new way is found to rationalize the real‐time observation of the generation and transformation of topological solitons using cholesteric LCs confined in patterned substrates. The experimental demonstration shows the topologically protected structures arise via the transformation of topological defects. Numerical modeling based on minimization of free energy closely reconstructs the experimental findings. The fundamental insights obtained from the direct observations pose new theoretical challenges in understanding the morphogenesis of different types of topological solitons within a broad range of scales.
binocular disparity is the most sensitive physiological depth cue for 3D objects with a size and distance of ≈10 m or less (Figure 1a). [5] Eyeglasses-based stereoscopy has been representative for raising binocular depth cues, but the vergenceaccommodation conflict limits their comfort and applicability significantly. [6] Recently, the holographic stereoscopic [7][8][9][10] and multiview displays [11][12][13][14] have been suggested as a promising alternative to the eyeglasses-based stereoscopic. The observation of the two different floating 2D holographic images by both eyes produces binocular disparity without the vergenceaccommodation conflict. However, conventional holographic stereograms using micrometer-scale pixels suffer from undesired multiple diffraction orders, that duplicate the same holographic images, and the narrowing of the viewing angle by only a few degrees. [7,15,16] To widen the viewing angle, complex optics, such as multiple spatial light modulators [8] and microlens arrays, [9] and their precise control are required.Optical metasurfaces consisting of meta-atoms arranged on the sub-wavelength scale can display holographic images over a wide viewing angle without multiple diffraction orders. [17][18][19][20] Owing to the large-scale integration of high-performance metaatoms, optical metasurfaces enable to manipulate the wavefront of light exquisitely without requiring complex optics and to implement a variety of 3D holograms with advanced features and functions such as polarization-/helicity-/angle-dependent multiplexing, [21][22][23][24][25][26][27] complete control of the holographic amplitude and phase, [28][29][30] bright, multicolor holography, [31][32][33] and active and programmable holograms. [34,35] However, research on metasurface-based 3D hologram displays has focused only on the creation of monocular depth cues so far. [19,28,30,32,35] In this research, we present a novel method based on optical metasurfaces to generate holographic stereograms addressing binocular depth cues. The optical metasurface consists of several hologram pieces which produce directionally propagating holographic wavefronts and display 2D holographic images suitable for stereopsis without mutual cross-talk ( Figure 1b). We developed a modified Gerchberg-Saxton (GS) algorithm involving a spatial Fourier filter to calculate the phase and amplitude distribution of the metasurface for holographic stereogram generation. The demonstrated metasurface displays a high-quality transmissive holographic stereogram of a 3D structure with a volume of 25 × 25 × 25 µm 3 over a wide viewing angle of more than ±30°. We expect that in the future, large-scale optical metasurfaces with enough meta-atoms to simultaneously produce all the monocular Holographic stereography providing binocular depth cues is one of the most promising technologies for 3D displays. However, conventional holographic stereograms based on micrometer-scale pixels suffer from multiple diffraction orders and narrow viewing angles. Optical metasurfaces with s...
A bilayer dichroic-doped liquid crystal (BDLC) film is fabricated via the uniaxial alignment method and a photopolymerization process. It is found to be useful in dichroic color filters, dual-mode circular polarizers, and chirality detectors. Two kinds of dichroic films with different absorbing wavelengths are cross-stacked to show various colors and contrasts depending on the polarization direction of the incident linearly polarized light, which is comparable with the conventional single-layer dichroic dye-doped (SDLC) film that only shows the contrast difference. This platform can be used in many other applications beyond the applications presented in this study, such as multicolor holograms, optical signal encryption, and electrically tunable devices.
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