Nematic liquid crystals of achiral molecules or racemic mixtures of chiral ones form flat films when suspended in submillimeter size grids and submerged under water. Recently, it has been shown (Popov et al., 2017) that films of nematic liquid crystals doped with chiral molecules adopt biconvex lens shapes underwater. The curved shape together with degenerate planar anchoring leads to a radial variation of the optical axis along the plane of the film, providing a Pancharatnam–Berry-type phase lens that modifies geometric optical imaging. Here, we describe nematic liquid crystal microlenses formed by the addition of chiral nanoparticles. It is found that the helical twisting power of the nanoparticles, the key factor to form the lens, is about 400 μm–1, greater than that of the strongest molecular chiral dopants. We demonstrate imaging capabilities and measure the shape as well as the focal length of the chiral nanoparticle-doped liquid crystal lens. We show that measuring the shape of the lens allows one to calculate the helical pitch of the chiral nematic liquid crystal and thus determine the helical twisting power of the chiral ligand-capped nanoparticles. Such measurements require the use of only nanograms of chiral nanoparticles, which is 3 orders of magnitude less than that required by conventional techniques. Since NPs are sensitive to external stimuli such as light and electric and magnetic fields, the use of chiral NPs may allow the achievement of tunable optical properties for such microlens arrays.

The isotropic to ferroelectric nematic liquid transition had been theoretically studied over one hun-dred years ago, but its experimental studies are rare. Here we present experimental results and theo-retical considerations...

use spatially varying refractive index profiles to vary the effective refractive index n(r) and therefore, the optical path, n(r) × d. In PB phase lenses, in the plane of the lens the azimuthal angle (β) of the director varies with radius in the plane normal to the light path [11] causing the radial component of the refractive index to vary as well.Convex [12,13] or concave [14] lenses, such as eyeglasses, have simple spherical surfaces, while Fresnel [15][16][17] lenses have complex shapes that contain portions of a sphere. Even with a perfectly designed and manufactured spherical lens profile, some distortion, called spherical aberration, is created for light that passes through the lens away from its center. To improve optical properties, aspheric lenses, [18][19][20] which gradually change the curvature from the center of the lens out to the edge, can be used. Aspheric lenses may be designed to eliminate spherical aberration, create a wider field of view, and deliver improved spot size [21] and better peripheral vision with a more compact, lighter design. [19,20,22,23] Although every surface that deviates from spherical symmetry is an aspheric surface, optical designers typically consider aspheres to be nonspheric, rotationally symmetric surfaces. Mathematically, they are frequently described using conic sections for the radial dependence of the surface, [24] where the radial dependence of the surface profile z(r) along the lens' axis is given in Equation (1) as

A highly sensitive label‐free liquid crystal (LC)‐based technique is presented for detecting Immunoglobulin G (IgG) antigens used to uncover viral infections. The effectiveness, sensitivity, and selectivity of this detection method is demonstrated with goat IgG antigen at concentrations as low as 100 pg ml−1, which is comparable to the sensitivity of the current enzyme‐linked immunosorbent assay (ELISA). The sensor is fabricated by decorating a transmission electron microscopy grid immobilized glass surfaces with antibodies; the target antigen is detected by a liquid crystal suspended onto the grid. This is different from previous methods where the antigen is detected either at the LC‐aqueous interface or in an LC sandwich cell with an antibody/antigen‐decorated substrate. This new approach has advantages such as easy sample preparation, higher sensitivity, and better storage capabilities. Binding the target antigen to the antibody results in a reorientation of the LC director that is detected optically. In addition to demonstrating the sensitivity, the physical principle of the detection is also discussed. This technique may apply to detect virtually any antigen of interest.

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