Magnetically actuated micropatterns for switchable wettability.

Arrays of actuated magnetic micropillars that can be tilted, twisted, and rotated in the presence of a magnetic field gradient were obtained. The type and extent of the movements are dependent on the distribution (isotropic, anisotropic) of the magnetizable particles inside the pillars and the strength and the direction of the magnetic field gradient. Independent motion of groups of pillars in the same or opposite directions or homogeneous motion of the whole pattern has been realized. Changing the pattern geometry causes changes in the roll-off angle (ROA) of water droplets on the surface. We show magnetically induced changes in the ROA and direction-dependent ROAs as a consequence of the anisotropy of tilted patterns. We also demonstrate transfer of microparticles between magnetically actuated neighboring pillars.