Dynamics of dielectric liquid rise between parallel electrodes under capillary and dielectrophoretic forces

An electric field can affect a dielectric fluid flow and this effect can be used especially in micro-devices. A differential second order equation for a temporal dependence of the liquid height-of-rise in a microchannel made of two parallel plates is modified to account for a liquid dielectrophoretic (LDEP) force, which is a result of an electric field occurring between the plates. This equation takes into account capillary, LDEP, inertial and gravitational forces for viscous, incompressible fluid. It is shown that the LDEP force between parallel electrodes does not depend on the meniscus shape. Time dependences of the height-of-rise, velocity of the liquid front and forces acting on the liquid are obtained for two cases of the initial liquid height and several voltage values applied to the plates, and presented in a dimensionless form. Numerical calculations and experimental verification are performed for isopropanol as a working liquid. We have found that for this liquid, adverse effects such as strong heating and boiling are small enough to observe the LDEP phenomenon between parallel electrodes. Results of the experiment conducted for a 5 mm long and 300 mu m wide channel with walls made of copper in the time interval 0-10 s, which is sufficient to achieve a stationary state, are presented. They are consistent with the theory within the voltage range up to 330 V. The highest achieved LDEP height-of-rise was about 13 mm. For higher voltage, Joule heating prevents from reaching a stationary state.