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Flow along superhydrophobic and liquid-infused surfaces: Theory versus reality

Time: Thu 2023-05-04 10.30 - 11.30

Location: Faxén, Teknikringen 8

Participating: Prof. Steffen Hardt (TU Darmstad)

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Abstract: Superhydrophobic and liquid-infused surfaces are micro-/nanostructured surfaces inspired by nature. Applications are found in the areas of water-repellency or drag reduction. In application scenarios, especially superhydrophobic surfaces have rarely met the expectations from theory or laboratory experiments. Liquid-infused surfaces were developed as a potentially more robust alternative that is less prone to the failure mechanisms superhydrophobic surfaces suffer from. In this presentation, I will first review some of the most important failure mechanisms of superhydrophobic and liquid-infused surfaces. After that, I will especially focus on the drag-reduction properties of those surfaces. While liquid-infused surfaces only promise moderate drag reduction, in idealized scenarios superhydrophobic surfaces show a very substantial drag reduction, expressed by effective slip-length values of the order of 100 μm. It has been known for many years that the stability of the Cassie wetting state poses severe limits on corresponding practical implementations of superhydrophobic surfaces. What has moved into the focus only recently is the fact that already minute amounts of surface-active contaminants can reduce the effective slip length very substantially, thus rendering the gas-liquid interface of the Cassie state almost immobile. I will explain the mechanism of surface immobilization by surfactants and compare different surface structures, especially transverse and longitudinal grooves.

Page responsible:Ardeshir Hanifi
Belongs to: FLOW
Last changed: May 02, 2023