Liquid microvortex generated around a laser focal point in an intense high-frequency electric field

A microvortex was discovered in liquid films when subjected to the combined action of a focused laser beam and a high-frequency electric field. The laser beam was perpendicular to both the surface of the liquid film and the direction of the electric field. The size of this opto-electrostatic microvortex (OEMV) in various liquids (water, ethanol, acetone, nitrobenzene) varied with the experimental conditions, but stayed in the 10-μm range. The velocity of the liquid flow in the vortex could be controlled by the intensity and frequency of the electric field (5.0×10⁴ to 0.8×10⁶ V/m, 2×10⁴ to 1×10⁶ Hz), by the laser power (0.01 to 2 W) and by the laser power density in the focal point. No microvortex was observed in benzene and chloroform. As an application of this phenomenon, single DNA molecules could be transported along the OEMV