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We demonstrate a rapid generation of twin opposing microvortices (TOMVs) induced by non-uniform alternating current (AC) electric fields together with a laser beam on a patterned pair of indium tin oxide (ITO) electrodes. A fast and strong jet flow region between twin microvortices is also generated. Its pattern and direction, such as whether it is symmetric or asymmetric, are controlled mainly by the location of a single laser spot relative to the ITO electrodes. With two laser beams, two separate flows are superposed to give a new one. In situ generation and control of the TOMV flow are tested in suspensions of fluorescent polystyrene particles, as well as in milk emulsions. This technique has great potential for dynamically manipulating micro-fluid flows, functioning as a micro-pump or mixer.

We demonstrate an opto-electrokinetic technique for noninvasive particle manipulation on the surface of a parallel-plate indium tin oxide (ITO) electrode that is biased with an alternating current (AC) signal and illuminated with near-infrared (1064 nm) optical landscapes. This technique can generate strong microfluidic vortices at higher AC frequencies (> 100 kHz) and dynamically and rapidly aggregate and pattern particle groups at low frequencies (< 100 kHz).