Dresden 2014 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 41: Poster - Pattern/ Nonlinear Dyn./ Fluids/ Granular/ Critical Phen.

DY 41.29: Poster

Donnerstag, 3. April 2014, 17:00–19:00, P3

Contact angle hysteresis of an evaporizing droplet: control with inkjet printing — Simeon Völkel, Thomas Müller, Ingo Rehberg, and •Kai Huang — Experimentalphysik V, Universität Bayreuth, 95440 Bayreuth, Germany

Wetting is ubiquitous in nature and of tremendous importance in industries such as mining, enhanced oil recovering, pharmaceutics, painting, and inkjet printing. Understanding the dynamics of wetting, such as contact angle hysteresis and pinning of the three phase contact line, can help to enhance the efficiency of various applications. Toward this goal, the challenge arises from the fact that most real life wetting phenomena are not in thermodynamic equilibrium. For example, the evaporation of a drop on a flat surface may lead to various drying patterns.

Here, we focus on the evaporation of a water drop on a surface of various materials and measure associated change of contact angle and drop size. In addition to evaporation, we employ an inkjet printing device to control the volume of the drop with an accuracy of nanoliter, in order to investigate the hysteresis of the contact angle and related pinning of the contact lines. It is found that the contact angle decays linearly with time during evaporation, provided that the contact line is pinned. In case of a smooth Polytetrafluoroethylene (PTFE) surface, the depinning drop shrinks with a fixed contact angle of around 90 degrees. Possible mechanisms accounting for such a phenomenon will be discussed.