(A): 2 micron silica spheres, H=200 micron, 1Hz SIN-wave, Amp=2.5V, DC V=4V. (AC component only made clouds and bands oscillate along the radial direction.) (B): 2.9 micron silica, H=200 micron. V=2.6V (after V=2.2V for 1.5 hours and V=2.6V for 1.5 hours).













background: AC voltage, bubble deformed the local electric field so that chains are along the surface direction instead of along up-down direction (electrodes are at up and down in the picture.)