Regensburg 2013 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 26: Focus: Wetting on smooth and rough surfaces: From spreading to superhydrophobicity II

CPP 26.3: Talk

Wednesday, March 13, 2013, 15:45–16:00, H34

Trapping and release of drops by electrically tunable wetting defects — Dieter 't Mannetje¹, Rudy Lagraauw¹, Simon Otten¹, Arun Banpurkar^{1, 2}, Arjen Pit¹, Dirk van den Ende¹, and •Frieder Mugele¹ — ¹University of Twente, Physics of Complex Fluids, MESA+ institute for Nanotechnology, Enschede, The Netherlands — ²University of Pune, Department of Physics, Pune, India

Drops driven across heterogeneous by gravity, viscous drag, and air flow can get stuck at pinning sites that are sufficiently strong compared to the external driving force. Using defects of continuously variable strength generated by electrowetting we study the critical conditions required to pin and depin drops of sliding down an inclined plane. We show that the strength of the electrical defects scales with the square of the applied voltage and with the radius of the drop. A generalized model incorporating the variable strength of the defect, viscous dissipation, and inertia of the sliding drop provides a general pinning criterion in excellent agreement with the experiments. We demonstrate the potential of electrically tunable defects as tools to manipulate and guide drops on inclined planes and in microfluidic devices.