Droplet velocities of several centimetres per second are observed in electrowetting microchannels, which is nearly two orders of magnitude higher than the velocities demonstrated by some other electrofluidic actuation principles.
They observed a maximum average velocity of 10 cm/s for transport of a droplet with an actuation of about 60 V, which was 2000 times faster than that reported for light driven motion and 40 times faster than with electrochemical actuation.
Because of the difficulties inherent in these micro-scale experiments, numerical simulations are useful in predicting the behaviour of droplets under electrowetting actuation. Zeng and Korsmeyer (2004) developed a model for the electrohydrodynamic forces.
This equation is also called the Lippmann equation, in which [[theta].sub.0] is the contact angle before the actuation. In order to achieve higher contact angle variations we must increase the voltage or the capacitance of the system.
In this paper we investigate the effect of electrode size, channel height, and voltage variations on droplet actuation.
For the numerical analysis, the effects of gaps between electrodes are assumed to be negligible; hence the actuation will be continuous.