Figure 1. Assembly of colloidal clay surface ribbon.

A silicone oil drop of radius 0.7 mm with Fh clay particles initially dispersed throughout the drop. The drop is immersed in castor oil. The arrows and crosses indicate the direction of the E-field. The four upper panels (a–d) are viewed perpendicular to the E-field direction, while the four lower panels (e–h) are viewed along the E-field direction. (a,e) Show the situation before the electric field is turned on, and (b–d) and (f–h) after a DC electric field is applied. Hydrodynamic circulation flows are observed in the drop, and in a few minutes clay particles are concentrated in a ribbon-shaped film on the drop surface.