Liquid crystal (LC) contact lenses are emerging as an exciting technology for vision correction. A homeotropically (vertical) aligned LC lens is reported that offers improved optical quality and simplified construction techniques over previously reported LC contact lens designs. The lens has no polarization dependence in the off state and produces a continuous change in optical power of up to 2.00 ± 0.25 D with a voltage applied. The variation in optical power results from the voltage-induced change in refractive index of the nematic LC layer, from 1.52 to a maximum of 1.72. One device substrate is treated with an alignment layer that is a mixture of planar and homeotropic polyimides, rubbed to induce a preferred director orientation in the switched state. Defects that could occur during switching are thus avoided and the lens exhibits excellent optical quality with a continuous variation in focal power.

Abstract:The superlatives of graphene cover a whole range of properties: electrical, chemical, mechanical, thermal and others. These special properties earn graphene a place in current or future applications. Here we demonstrate one such application -adaptive contact lenses based on liquid crystals, where simultaneously the high electrical conductivity, transparency, flexibility and elasticity of graphene are being utilised. In our devices graphene is used as a transparent conductive coating on curved PMMA substrates. The adaptive lenses provide a +0.7 D change in optical power with an applied voltage of 7.1 V rms -perfect to correct presbyopia, the age-related condition that limits the near focus ability of the eye. Frye, R. Pashaie, S. Thongpang, Z. Ma, and J. C. Williams, "Graphene-based carbon-layered electrode array technology for neural imaging and optogenetic applications," Nature Commun. 5, 5258 (2014).

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Here we present a detailed ab initio study of two experimentally synthesized bismuth niobate BiNbO4 (BNO) polymorphs within the framework of density functional theory (DFT).

The three refractive indices of a liquid crystal that exhibits lamellar analogues of the threedimensional isotropic, nematic, and smectic A phases are reported as functions of temperature for the Lam-I and Lam-N phases. The data suggest a number of striking behaviour types. The orientational distribution of the mesogenic moieties becomes more highly peaked in two dimensions on cooling from the Lam-I to the Lam-N phase; the twodimensional order associated with mesogenic director n in the Lam-N phase is weak; and conformational changes in the side chain result in an increase in the refractive index perpendicular to the lamellae with decreasing temperature in the Lam-N phase.

Articles you may be interested inFast determination method of cell thickness and time-dependent twist angle in twisted-nematic liquid-crystal cells Rev. Sci. Instrum. 77, 043901 (2006); Induced nematic phase in a polymer/liquid crystal mixture A micro-or nanopatterned planar-aligned cell ordinarily requires a pair of mirror-image patterned substrates that must be aligned in register to Ӷ1 m. As an alternative we examine the director orientation profile of a nematic liquid crystal in a cell composed of one substrate whose easy axis is patterned on micrometer length scales and a second substrate treated for planar degenerate alignment using polymethyl methacrylate. For cell thickness Ͻ, the experimentally measured director profile in the bulk corresponds approximately to that imposed at the micropatterned substrate. The results are compared with theoretical calculations. This method provides an excellent alternative to the use of a pair of substrates aligned in close register.

A comprehensive density functional theory guided experimental study of copper bismuth oxide CuBi2O4 to gain a better understanding of its functional properties relevant to photocatalytic activity.

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