Metamorphosis of trilobite-like drops on a surface: Electrically driven fingering

The experimental evidence reveals that sessile drops on a dielectric horizontal substrate subjected to sub-critical in-plane electric field acquire steady-state configurations where balance between the pulling-outwards Maxwell stresses and restoring surface tension has been attained. On other hand, experiments show in supercritical become dominant not only stretch drop as whole but also trigger growth of multiple fingers crawling toward electrodes both sides drop. This makes with stretched along lines similar some trilobites known from their imprints petrified sediments studied paleontology. It is shown experimentally theoretically are triggered during encounters spreading outlines minor imperfections. Such defects (existing originally or pre-notched purpose) result which can grow being directed by electric-field lines. present work details observations trilobite-like fingering several types commercially available paints (colloidal dispersions) provides theoretical framework for this novel type fingering.