How nanoparticles affect flow through porous stuff in surprising ways

Viscous fingering occurs in porous media where fluids of differing viscosity converge in finger-shaped patterns as a result of growing disturbances at the interface. Such instabilities are encountered in a wide variety of fields. Understanding different aspects of this phenomenon, and the variables that can control things like instabilities and velocity distribution dynamics, can potentially offer options to control and utilize these effects more effectively.

(via WSJ)