Bistable guest-host liquid crystal device enabling transparent and opaque dual states by tilt-twist director switching

초록

A bistable guest-host liquid crystal (GHLC) device capable of transparent and opaque dual optical states is demonstrated through controlled tilt-twist director transitions. The cell incorporates a low-birefringence nematic host (Delta n ti 0.03), a dichroic dye, and a chiral dopant tuned to a pitch ratio of d/p = 1.1, enabling two distinct field-off configurations: a high-tilt transparent state and a nearly 180 degrees twisted absorbing state. Patterned electrodes generate horizontal and vertical electric fields that selectively induce azimuthal twisting or reorientation toward a tilted homeotropic-like alignment. Elastic free-energy calculations confirm the presence of two stable minima corresponding to the observed optical states. Optical measurements reveal a high transmission in the tilted state and strong attenuation in the twisted state, with the contrast ratio further adjustable through dye concentration. Both states exhibit robust memory behavior under zero applied voltage and can be repeatedly switched with low driving voltage. The proposed bistable GHLC structure offers an absorption-based optical switching platform suitable for energy-efficient smart windows and light-control applications.

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