Competitive Electrowetting of Polymer Surfaces by Water and Decane

Abstract

The present study deals with electrocapillarity effects in the three-phase system water-decane-polymer. This system consists of a decane droplet which adheres under water on a polymer surface. We applied an electric potential between an electrode beneath the polymer film and a platinum electrode immersed in the water. The polymer film acts as insulator: no steady electrical current flows between the electrodes. When the voltage is increased, the contact angle of decane and water changes, in some cases by up to 100°. The shape of the electrowetting curve (contact-angle cosine versus voltage plot) strongly depends on the type of the polymer. A saturation at higher voltages, connected with a hysteresis, is interpreted in terms of charge carrier injection into the polymer surface. Other deviations of the experimental results from the Lippmann-Young parabola concern a broadening with the polyolefins, a strong shift, and apparent reduction to one branch with two fluoropolymers, and for PET and a heavily oxidized PE sample the deviations concern a nearly zero dependence of the voltage.

Capillary and electrostatic limitations to the contact angle in electrowetting-on-dielectric

“…5b) the situation is different: numerical predictions are larger then analytical values, which agrees with data presented in Papathanasiou and Boudouvis (2005). This is contrary to the majority of experimental results published in literature, where very close agreement is usually observed, although in a few cases there was a noticeable difference (Blake et al 2000;Janocha et al 2000;Seyrat and Hayes 2001). In the first case the cosh versus V 0 curve is still quadratic, but with a coefficient twice smaller than that theoretically predicted.…”

“…A similar effect on the contact angle saturation may be created by electric charges trapped in the dielectric film-a theory developed in (Verheijen and Prins 1999b) successfully related the magnitude of trapped charges with the angle saturation. Results presented in (Janocha et al 2000) support the possibility of charge injection into the polymer film, which can also be responsible for the contact angle hysteresis effect. Evidence of the presence of the electric charges has been found using photocopier toner powder (Decamps and De Coninck 2000).…”

“…The results in Papathanasiou and Boudouvis (2005) seem to indicate that the contact angle saturation can be attributed to the dielectric breakdown [although in Janocha et al (2000) this possibility was ruled out]. The motivation for the above theory was provided in Seyrat and Hayes (2001), who linked the saturation effect to a material deficiency.…”

Bubble actuation by electrowetting-on-dielectric (EWOD) and its applications: A review

“…This phenomenon is called contact angle saturation in EWOD. [50][51][52][53][54][55] While several hypotheses have been advanced to explain it, it has yet to be clearly understood. For more details on this phenomenon, refer to other review articles.…”

Insight into the micro scale dynamics of a micro fluidic wetting-based conveying system by particle based simulation

“…1) (Berge 1993;Nakamura et al 1973Nakamura et al , 1977Janocha et al 2000;Kim 1999, 2000;Kim 2001;Lee et al 2002). A motion of the droplet's contact line results (Dimitrakopoulos and Higdon 1997;Vallet et al 1999;Decamps and Coninck 2000;Schneemilch et al 2000), and if the wetting modulation on the contact line is inhomogenous, a fluid motion can be observed (Moriarty et al 1991;Ivošević and Ž utić 1998).…”