Synopsis: Patterns of breakup

Numerical calculations show a variety of scenarios for how intact liquid structures on patterned surfaces can break apart and become detached to allow motion.
Synopsis figure
Credit: P. Beltrame et al., Phys. Rev. E (2010)

Motion of liquid on chemically patterned surfaces is of vital interest in designing microfluidic components and devices for biological applications such as cell analyzers. Of particular importance is how droplets and liquid ridges move along regularly structured surfaces: Do they stay intact or break up owing to instabilities? One scenario is that the drops or ridges remain stuck to areas that are “hydrophilic” until some external force causes depinning and the liquid object moves to another location. In a paper in Physical Review E, Philippe Beltrame at the University of Avignon, France, and colleagues in the US, Germany, and the UK report their numerical studies of how ridges and droplets behave under various conditions of driving force and patterning.

Beltrame et al. model these scenarios by calculating how liquids move past parallel water-repelling stripes when a force is applied parallel to the substrate and perpendicular to the stripes. The driven liquid ridges move in the direction of the force (for instance, down an inclined substrate). The authors find that in some cases the ridges become depinned and pass the stripe intact, or in other cases may break up into droplets before depinning, and only then move towards the next stripe. All in all, Beltrame et al. find seven distinct transition regimes for this behavior. This diversity shows that in addition to requiring a clear understanding of the different kinds of heterogeneities that may cause the pinning, the complex coupling between pinning force and surface of the fluid also has to be taken into account. – David Voss


More Features »


More Announcements »

Subject Areas

Fluid Dynamics

Previous Synopsis

Next Synopsis


What lies beneath

Read More »

Related Articles

Focus: <i>Video</i>—Swimming Snails Use Insect-like Flapping
Fluid Dynamics

Focus: Video—Swimming Snails Use Insect-like Flapping

The unusual wing flapping of submerged “sea butterflies” is similar to that of birds and insects and may provide signs of climate stress. Read More »

Focus: Asymmetry Helps Tiny Rods Swim Upstream
Biological Physics

Focus: Asymmetry Helps Tiny Rods Swim Upstream

Changing the length ratio of the two segments of a microswimmer affects its ability to automatically swim against the current. Read More »

Synopsis: Telling Whiskey from Whisky
Fluid Dynamics

Synopsis: Telling Whiskey from Whisky

The evaporation of a drop of American whiskey leaves a characteristic web-like pattern that isn’t observed in Scotch whisky and other distillates. Read More »

More Articles