Realizing Temperature-Controlled Digital Microfluidic Chips with Versatile Microelectrodes

Droplet heating and pumping were performed on a versatile microelectrode by selectively applying appropriate electric signals. The designed electrode is in a meander-line shape and covered by an insulator. On the one hand, when a potential difference is applied along the electrode, power dissipated by the resistance of the electrode causes droplet heating. On the other hand, when an electric field exists across the insulator above the electrode, the charges stored in the capacitor alter the surface wettability and pump droplet. Manipulated droplets were placed between parallel plates with passivated versatile microelectrodes on the bottom plate and a Teflon-coated blank ITO on the top plate. We successfully applied a DC voltage at the two terminals of the meander-line electrode to heat up the electrode as well as the droplet above. Besides, pumping droplets by EWOD was demonstrated by applying a proper AC voltage between the electrode on the bottom plate and the ITO on the top plate. With the proposed versatile microelectrode design and actuation scheme, heating and EWOD were obtained on an identical electrode. A digital microfluidic chip capable of droplet manipulation by EWOD and droplet heating was presented.