Regular to chaotic transition of stick-slip motion in sliding friction of an adhesive gel-sheet.

Spatio-temporal pattern of the stick-slip motion of a gel-sheet pulled on a glass substrate is observed. The sliding takes place via the propagation of the wave of detachment (Schallamach wave). At large pull velocity, the detached region is a stripe which moves regularly with constant speed and the frictional force shows a periodic time dependence.