Electric-field-assisted interfacial rubrene self-assembly for continuous tuning of liquid crystal pretilt angles

This study demonstrates a contact-free, low-temperature strategy for continuously tuning the pretilt angle of nematic liquid crystals (LCs) via electric-field-assisted capillary filling combined with rubrene self-assembly. By applying an AC electric field (0–5 V) across unrubbed, polyimide-free indium tin oxide (ITO) cells during LC injection, the pretilt angle of a rubrene-doped nematic LC mixture can be continuously programmed from approximately 3° (near-planar) to 90° (homeotropic). Contact-angle analysis reveals that increasing the filling voltage dramatically alters the interfacial interaction from a polar-dominated surface to a nonpolar, high-dispersive regime, resulting in a gradual transition from planar to homeotropic LC alignment. Electro-optical and dielectric measurements confirm stable, uniform LC alignment and customized threshold responses across cycles. This field-imprinted interfacial assembly method eliminates mechanical damage and high-temperature thermal processing, offering a scalable route for next-generation flexible, wearable, and tunable photonic devices