Two-liquid wetting and phase electrowetting as a probe for surface chemistry of hydrophobic materials.

Two-liquid contact angle measurement and electrowetting under low frequency are two measurement methods extremely sensitive to surface polarity and charge density. The theory underlying these two methods are described and have been applied to hydrophobic coatings. By combining these two methods, we successfully demonstrated the variations of the surface properties of polymer-based hydrophobic coatings when exposed to different chemical environments (pH modification or molecular grafting) with real-time phase electrowetting measurements.