Opto-electrohydrodynamic control of rapid microvortex flow

Rapid and tunable opto-electrohydrodynamic (OEHD) microvortex flow generation and manipulation have been recently developed. The combination of AC electric fields and optical illumination allows for the easy and rapid creation of microvortex flows inside a microchannel for applications such as micropumping and micromixing. An opto-electrohydrodynamically generated microflow called a twin opposing microvortex (TOMV) flow has been simply manipulated and tuned by varying AC voltage and frequency as well as laser power and moving laser beam inside a TOMV device. Micron-resolution particle image velocimetry (μPIV) is used to measure velocity fields of three-dimensional (3D) microvortex flow generated under non-uniform electric fields and a highly focused laser beam. The magnitude of the in-plane velocity linearly depends on AC voltage while it shows a bell-shaped curve when the magnitude of the in-plane velocity is expressed as a function of AC frequency. When the AC frequency is increased to a few MHz, different microvortex flows are generated. The results presented are useful to understand underlying fluid mechanics in the TOMV flow and will be a foundation to develop effective and controllable microvortex flow in the rapidly growing field of micro/nano scale transport.