  Stimuli-responsive liquid crystal elastomers (LCEs) with a strong coupling of
orientational molecular order and rubber-like elasticity, show a great
potential as working elements in soft robotics, sensing, transport and
propulsion systems. We demonstrate a dynamic thermal control of the surface
topography of LCE coatings achieved through pre-designed patterns of in-plane
molecular orientation. These patterns determine whether the LCE coating
develops elevations, depressions, or in-plane deformations. The deterministic
dependence of the out-of-plane dynamic surface profile on the in-plane
orientational pattern is explained by activation forces. These forces are
caused by two factors: (i) stretching-contraction of the polymer networks
driven by temperature; (ii) spatially varying orientation of the LCE. The
activation force concept brings the responsive LCEs into the domain of active
matter. The demonstrated relationship can be used to design programmable
coatings with functionalities that mimic biological tissues such as skin.
