ELECTROMECHANICS OF MICROFLUIDIC DEVICES: ELECTROWETTING AND LIQUID DIELECTROPHORESIS

Electrical forces exerted on liquids are ideally suited for exploitation in microfluidic devices due to the favorable scaling of these forces as device dimensions are reduced and also because flow control can be readily achieved by adjusting voltage and frequency. Of particular interest nowadays are schemes using droplets as the basic unit of transport, manipulation, and processing. Two related electromechanical effects - electrowetting on dielectric-coated electrodes (EWOD) and liquid dielectrophoresis (DEP) - show particular promise in droplet-based microfluidics. These phenomena, intimately connected through electrical frequency and conductivity, can be exploited to manipulate and control small liquid volumes in applications ranging from film coating and line printing to dispensing sub-nanoliter liquid aliquots containing biological materials to formation of double-emulsion droplets for laser targets. EWOD and DEP actuation offer a surprisingly wide range of phenomenology relevant to practical microfluidic systems.