Slippage of Newtonian liquids: Influence on the dynamics of dewetting thin films

TL;DR

This study investigates how slip length influences the dewetting dynamics of Newtonian polystyrene films on different substrates, providing a new analysis method and quantifying slip lengths relevant for microfluidic applications.

Contribution

The paper introduces a novel analysis method to measure slip length and compares dewetting dynamics on substrates with different slip properties, advancing understanding of liquid slippage.

Findings

Dewetting velocity is higher on DTS than on OTS due to larger slip length.

Slip lengths range from 400 nm to 600 nm depending on substrate and temperature.

Different substrates significantly affect the dewetting behavior of polystyrene films.

Abstract

Slippage of Newtonian liquids in the presence of a solid substrate is a newly found phenomenon the origin of which is still under debate. In this paper, we present a new analysis method to extract the slip length. Enhancing the slip of liquids is an important issue for microfluidic devices that demand for high throughput at low pumping power. We study the velocity of short-chained liquid polystyrene (PS) films dewetting from non-wettable solid substrates. We show how the dynamics of dewetting is influenced by slippage and we compare the results of two types of substrates that give rise to different slip lengths. As substrates, Si wafers were used that have been coated by octadecyl-trichlorosilane (OTS) or dodecyl-trichlorosilane (DTS), respectively. Our results demonstrate that the dewetting velocity for PS films on DTS is significantly larger than on OTS and that this difference originates from the different slip lengths of the liquid on top of the two surfaces. For PS films of thicknesses between 130 nm and 230 nm we find slip lengths between 400 nm and 600 nm, depending on substrate and temperature.