Microwave Induced Water Flows in Microsystems
Antonio Ramos
Department of Electronics and Electromagnetism
Univeristy of Seville
Abstract:
Alternating current electric fields are of increasing interest for the actuation of liquids in microsystems. In this work, we investigate how microwave fields can induce water flow in microsystems. We place a drop of water on two parallel coplanar microelectrodes that are energized by a microwave generator. Water is heated because of its significant dielectric loss at microwave frequencies. The generated gradients of temperature produce spatial variations in mass density and dielectric permittivity leading, respectively, to buoyancy and dielectric forces in the liquid. The observed fluid flow patterns demonstrate that both effects are taking place at different length scales: the dielectric forces dominate at lengths of the order of 100 microns or smaller, while buoyancy dominates around 1 mm. The microwave liquid actuation can be used for pure water as well as for water saline solutions, such as bio-fluids. Therefore, it is of interest for the Lab-on-a-Chip technology.