Light controlled friction at a liquid crystal polymer coating with switchable patterning

We describe a new methodology that enables dynamically control of motion through modulating friction at coating surfaces by exposing with UV light. The principle is based on reversibly switching the surface topographies of the coating by light. The coating surface transfers from flat in the dark to corrugated in the presence of UV by forming regular ridge-like line gratings. Both the static and the kinetic friction coefficients are investigated in a dynamic manner by switching between the off (flat surface) and the activated (with ridges) state. By dynamically changing the friction, we are able to bring the sample from a static state into motion via UV exposure. When in motion, the friction coefficient can be altered further by modulating the light conditions. E.g. a smooth sliding can transfer into an interlocking state, or vice versa. Moreover, we can dynamically reduce the contact area in the interface and thus lowering friction forces.