Scaling fundamentals and applications of digital microfluidic microsystems
With the first experimental demonstration of droplet flow on an electrowetting-on-dielectric (EWD) array platform in 2000, there has been significant interest in droplet actuation for lab-on-a-chip applications. A hydrodynamic scaling model of droplet actuation in a EWD actuator is presented that takes into account the effects of contact angle hysteresis, drag from the filler fluid, drag from the solid walls, and change in the actuation force while a droplet traverses a neighboring electrode. Based on this model, it is shown that scaling models of droplet splitting, actuation, and liquid dispensing all show a similar scaling dependence on [t/εr(d/L)]1/2, where t is insulator thickness and d/L is the aspect ratio of the device. It is also determined that reliable operation of a EWD actuator is possible as long as the device is operated within the limits of the Lippmann-Young equation. Also discussed are fluidic operations possible with digital microfluidics. Significant advances have been made in chip technology that allow for users to access digital microfluidic chips and to program these chips to perform numerous operations and applications on a common array of electrodes. Whereas in the past, microfluidic devices have been application specific, lacking reconfigurability and programmability, today's digital microfluidic chips enable versatile, reconfigurable chip architectures that are capable of accommodating and adapting to multiple applications on the same platform. © Springer Science + Business Media B.V. 2010.
