Optimization of electrowetting electrodes: Analysis of the leakage current characteristics of various dielectric layers

Electrowetting is a phenomenon that has attracted much attention in recent years for application in lab-on-a-chip devices. The electrical control of contact angle can be used to transport liquid droplets by capillary forces. We present experimental work that aims to clarify the role played by the dielectric breakdown of surface coatings. The relation between electrowetting and dielectric breakdown was tested by means of measuring the contact angle of a droplet of water placed between two electrodes on an insulated surface. The current and resistance between these electrodes was measured as a function of applied voltage for the following dielectric coatings: silicon dioxide, silicon nitride and parylene.