Wrinkled labyrinths in critical demixing ferrofluid

WILKE, NATALIA; BUGASE, JONAS; TREFFENSTÄDT, LISA-MARIE; FISCHER, THOMAS M.

SOFT MATTER

ROYAL SOC CHEMISTRY

Año: 2017 vol. 13 p. 7307 - 7307

1744-683X

thin film of a critical ferrofluid mixture undergoes a sequence of transitions in a magnetic field. First the application of a field induces a critical demixing of the fluid into cylindrical droplets of the minority phase immersed in an extended majority phase. At a second critical field the cylindrical shape is destabilized and transforms into a labyrinth pattern. A third wrinkling transition occurs at even higher field if the liquid has a liquid/air interface. The wrinkling is absent if the droplet has a cover-slide on top. We explain the wrinkling by the wetting behavior of the liquid/air interface that shifts the surface region away from a critical demixing point.