Plasma-enhanced electrowetting-on-dielectrics

The wettability of droplets on a dielectric surface can be enhanced by an external electrical signal. Previous research has suggested that such a change in surface wettability is caused by the Maxwell stress concentrated on the three-phase contact line (TPL) of the droplet. Here, we demonstrate that this electromechanical effect cannot fully explain the complex process of droplet contact angle variation. The discharge plasma near the TPL is found to have a significant influence on the contact angle variation. When combined with the Maxwell stress, the plasma discharge can significantly enhance wetting, termed as plasma-enhanced electrowetting-on-dielectrics (PE-EWOD). The conditions for the plasma generation are described, and a phase-like diagram is used to clarify the relationship between PE-EWOD, EWOD, and electrolysis, which is helpful for an adequate control of the wettability through voltage. These findings have important implications for controlling droplet motion in numerous applications, including micro/nano manufacturing, optics, biomedicine, heat dissipation, and electronics.