Magnetically reconfigurable colloidal patterns arranged from arrays of self-assembled microscopic dimers

This article presents a bottom-up strategy to assemble microscale paramagnetic particles into colloidal dimers above a structured magnetic substrate. Application of an external magnetic field modifies the stray field of the substrate, and generates several complex structures such as herringbone patterns, trees, branched or buckled chains, resulting from the competition between magnetic dipolar interactions and pinning of the substrate. Finally, the realized colloidal patterns are used to control and switch the mobility of non-magnetic colloids floating above the assembled paramagnetic dimers.