Low Friction Flows of Liquids at Nanopatterned Interfaces

TL;DR

This paper demonstrates that nanometer-scale surface patterning and wetting properties can significantly reduce fluid friction at interfaces, challenging previous assumptions and enabling improved microfluidic device performance.

Contribution

It reveals that surface roughness and wetting can enhance slip and reduce friction, introducing a novel approach to control flow resistance at the nanoscale.

Findings

Nanopatterned surfaces drastically increase fluid slippage.

Surface roughness can reduce, not increase, friction.

Potential to control nanobubbles for flow regulation.

Abstract

With the recent important development of microfluidic systems, miniaturization of flow devices has become a real challenge. Microchannels, however, are characterized by a large surface to volume ratio, so that surface properties strongly affect flow resistance in submicrometric devices. We present here results showing that the concerted effect of wetting . properties and surface roughness may considerably reduce friction of the fluid past the boundaries. The slippage of the fluid at the channel boundaries is shown to be drastically increased by using surfaces that are patterned at the nanometer scale. This effect occurs in the regime where the surface pattern is partially dewetted, in the spirit of the 'superhydrophobic' effects that have been recently discovered at the macroscopic scales. Our results show for the first time that, in contrast to the common belief, surface friction may be reduced by surface roughness. They also open the possibility of a controlled realization of the 'nanobubbles' that have long been suspected to play a role in interfacial slippage