Spontaneous and stable uniform lying helix liquid-crystal alignment

Abstract

The flexoelectro-optic effect in the uniform lying helix (ULH) geometry could provide many advantages over existing liquid-crystal technologies, however reliably forming the ULH has been problematic. Here, we achieve spontaneous, stable, and repeatable ULH alignment for materials with both positive and negative dielectric anisotropy in devices ranging from 1 to 7 μm in thickness without the need for any field application or flow-induced alignment, using a combination of weak homeotropic alignment conditions and unidirectional grooved surface profiles. The technique requires slow cooling from the isotropic phase and through the blue phase. Devices made using the technique display sub-millisecond and linear electro-optical responses.

Giant Flexoelectro-optic Effect with Liquid Crystal Dimer CB7CB

“…A well-aligned ULH CLC texture can be obtained by application of pulsed electric field with empirically optimized duration and magnitude to the sample cell91819. Alternatively, a spontaneous formation of the ULH CLC texture have been demonstrated by treatment of the surface of substrates creating periodic micro-grooves1525, periodic anchoring conditions1426, controlling pretilt angle of LC molecules27, periodic polymer channels28 or polymer walls29.…”

Voltage-controlled formation of short pitch chiral liquid crystal structures based on high-resolution surface topography

“…This approach could be further exploited in the future by using different cell thicknesses, different thicknesses of the resist layer and different patterned electrodes and could be very interesting for application in electro-optic devices such as diffraction gratings, lasers and displays. Short pitch ULH-like structures are especially interesting to develop in-plane emitting CLC lasers and displays based on fast flexoelectro-optic switching [18,34,35,36]. Depending on the lateral dimensions that are envisioned, e-beam lithography could also be replaced by conventional UV lithography.…”

P.99: Alignment Peculiarities of Cholesteric Liquid Crystals on the Surfaces Processed by Plasma Beam

“…The method is also effective for the alignment of CLC in ULH configuration. The developed approach is rather similar to that in [11], where a weak homeotropic anchoring and anisotropic relief of the aligning layers are combined. Macroscopically and microscopically uniform ULH textures stable over long period of time are obtained.…”