Manipulation of liquid crystal droplets by optoelectronic tweezers

Optoelectronic tweezers (OETs) by using the light-induced dielectrophoresis (DEP) have been applied to control the isotropic objects with sizes from nanometers to micrometers. The ability to control anisotropy and birefringent materials like liquid crystals (LC) by OETs is promising for finding more photonic applications. Unlike conventionally manipulated isotropic objects, the LC directors inside the LC droplet are influenced by the external electric field during OETs operation. We have demonstrated that LC droplets in an aqueous solution can be dynamically manipulated and patterned by OETs even though the LC directors inside the droplet are changed with the external electric field. The propulsion speeds of the LC droplets in terms of droplet size, light pattern linewidth, strength and frequency of the applied electric field are characterized by applying a rectangular light pattern. A velocity of 180 μm/s is achieved for a 30-μm-diameter LC droplet by applying 6.5 V at 20 kHz.