Crushing Ferrofluidic Emulsions Without a Magnetic Field and Observing Viscous Fingering Patterns

Usually, viscous fingering emerges when a lower viscous fluid is pushed through a higher viscous fluid. We show that viscous fingering also occurs when compressing nanoparticle-stabilized ferrofluidic emulsions in the absence of a magnetic field. We investigate details of the fingering patterns and how these patterns correlate with discrete numbers of groups of emulsions. That is, we examine the fingering patterns for a single emulsion, two adjacent emulsions, three adjacent emulsions, and so on, after they are crushed. As far as we know this is the first observation of viscous fingering due to crushed 'solid-like' emulsions on a dry substrate