Figure 1.

Optical images showing the tumbling motion of particle chains. A chain of four particles circled in red moves with the flow in a gap region (a) near the edge of an electrode (b), above the electrode off to the upper side (c), at the center the electrode (d), off the lower side (e), and near the other edge of the electrode (f). (g–h) The tumbling motion of particle chains with different sizes and colors. (i) Schematic illustration of the tumbling motion of a particle chain. The trailing end of the chain gets lifted up to form an angle with the floor and stand straight at the center of electrodes and, after that, the chain gradually tumbles back as it moves into the next gap region.