Showing papers by "Friedrich Gunther Mugele published in 2012"
TL;DR: In this paper, the formation and stability of stearic acid (SA) based films on aqueous sub-phases via Langmuir trough and imaging ellipsometry experiments were studied.
45 citations
TL;DR: The contact angle of water drops on substrates for which the wettability is dominated by van der Waals forces remains unchanged when the substrates are coated with a monolayer of graphene as mentioned in this paper.
Abstract: The contact angle of water drops on substrates for which the wettability is dominated by van der Waals forces remains unchanged when the substrates are coated with a monolayer of graphene. Such 'wetting transparency' could lead to superior conducting and hydrophobic graphene-coated surfaces with tunable electronic properties.
23 citations
TL;DR: This paper shows how electrowetting on dielectric can be used to monitor a dynamic liquid-liquid interfacial tension (IFT) with a time resolution of O(1 s) using amplitude modulation of the AC voltage.
Abstract: The adsorption of surface active species to liquid–liquid and to solid–liquid interfaces can have dramatic effects in microfluidics. In this paper we show how electrowetting on dielectric can be used to monitor a dynamic liquid–liquid interfacial tension (IFT) with a time resolution of O(1 s) using amplitude modulation of the AC voltage. This straightforward method, which requires less than a microlitre of sample, is demonstrated for aqueous drops containing Triton X-100 surfactant on a Teflon AF-coated substrate and with heptane as the immiscible oil ambient. Under these conditions, next to extracting the oil–water IFT (γow), also the effective water–substrate IFT difference (Δγws) can be obtained from the oil–water IFT and the Young's angle. Both γow and γws decrease over time due to adsorption. The measured dynamic oil–water IFT compares well to results of pendant drop experiments.
12 citations
17 Jan 2012
TL;DR: In this paper, a simple analytical model for axisymmetric cavities and small deflections of the liquid menisci within the cavities reveals the existence of a novel electric-field-driven instability of the surface.
Abstract: We study possible mechanisms of the transition from the Cassie state to the Wenzel state on superhydrophobic surfaces under the influence of electric fields as a function of the aspect ratio and the wettability of the surface. A simple analytical model for axisymmetric cavities and small deflections of the liquid menisci within the cavities reveals the existence of a novel electric-field–driven instability of the liquid surface. Fully self-consistent calculations of both electric-field distribution and surface profiles show that this instability evolves from a global one towards a local Taylor cone-like instability for increasing aspect ratio of the cavities. A two-dimensional map is derived indicating the prevalence of the interfacial instability as compared to the depinning scenario of the three-phase contact line, which is well known from ordinary superhydrophobic surfaces
2 citations