Crack formation in Laponite gel under AC fields

Crack formation patterns in Laponite gel are known to be strongly affected by electric fields produced by a DC (direct current) source. It can be shown that AC (alternating current) fields produce equally remarkable patterns in a radially symmetric set-up. The character of the pattern depends crucially on the field strength. A significant feature observed is the bending of radial cracks, with the curvature increasing as field strength is increased. Voltages of 20 to 70 V have been applied and several features of the resulting patterns quantified. Striations on the fracture surfaces and crack speeds are also studied.