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 26.2: Talk

Wednesday, March 13, 2013, 15:30–15:45, H34

Directed motion of droplets on asymmetrically structured vibrating substrates: a Molecular Dynamics study — •Nikita Tretyakov and Marcus Müller — University of Göttingen

We study a transport of coarse-grained polymer droplets on asymmetrically structured (sawtooth shaped) and vibrating substrates by means of Molecular Dynamics. The temperature of the system is controlled by the DPD thermostat. Due to a continuous supply of power by substrate vibrations and the asymmetry of its topography, the droplets are driven in a preferred direction. This directed motion is investigated as a function of the size of the droplets, linear dimension of the substrate corrugation and the period of substrate vibrations. To this end, our main concern consists in resolving two questions: (i) what is the driving mechanism and (ii) what is the character of the flow inside the droplet?

A typical mechanism of driving is the one provided by droplet's contact lines, as the responses of the advancing and receding contact lines on the vibrating asymmetric substrate are not identical. We, moreover, find a range of vibration periods that lead to an additional driving by the contact area of the substrate between the contact lines.

For the character of the droplet motion there are, in general, three possibilities: sliding, rotating and a combination of both. All of them dissipate the input power by different means. We find that for most of the parameters the droplets are sliding, but the linear size of the substrate corrugation may give a rise to an additional rotation.