More about the electromechanics of electrowetting

Classical lumped parameter electromechanics successfully models most observable phenomenology of droplet-based electrowetting and liquid dielectrophoresis. The key to this unifying approach is to express capacitance in terms of the proper mechanical variable. While this capability is easily revealed in modeling microfluidic schemes, where the electrical force drives center-of-mass motions of the liquid, lumped parameter electromechanics also can be adapted for devices such as the liquid lens, where a liquid mass is made to change its shape and is characterized by observable changes in the apparent, liquid/solid contact angle. Because capacitance is usually insensitive to contact angle, irregularities of the liquid configuration, and fringing fields, electromechanical modeling is easy to use. For the case of liquids of finite electrical conductivity, a capacitive- and resistive-based model can be used to predict frequency-dependent effects.