Voltage-expandable liquid crystal surface

Abstract

Based on dielectrophoretic effect, we report a novel approach which can extensively spread a liquid crystal (LC) interface. With interdigitated striped electrodes, the droplets can be stretched along the striped electrode direction; while with zigzag interdigitated electrodes, the droplets can be further stretched sidewise. In our demonstration, the occupied area of a 1.9-mm-aperture LC droplet doped with 1.2 wt% black dye could be expanded over ∼3.5× at 78 V_rms. The spreading and recovering times were measured to be ∼0.39 s and ∼0.75 s, respectively. The slower response time confirms the extreme expanding of the LC surface. The contrast ratio is over ∼120 : 1 in transmissive mode. Color light switch was also demonstrated by spreading colored-dye doped LC droplets. The mechanical stability of the device was also evaluated. Liquid devices based on this cell structure have the advantages of good stability, simple operation and low power consumption. This work opens a new gateway for voltage controllable, polarization-insensitive, and broadband liquid photonic devices which may find numerous applications in switchable windows, variable optical attenuators, and displays.