Fig. 4: Colloidal molecules with metallic bonds.
From: Active colloidal molecules assembled via selective and directional bonds
a Cartoon showing the side and top view of an AB colloidal molecule with the metallic bond, by patchy particle P3 and the 4-µm central sphere. b Finite-element analysis showing the p-DEP attraction between the metallic lobe and the sphere stabilizes the bond. Red arrows represent the direction of electric field lines. Color bar: electric field strength. c Optical microscope images of colloidal molecules with metallic bonds (AB1 to AB7). d The formation kinetics of a metallic bond, showing that P3 approaches and touches the big sphere with its dielectric lobe, slips along the rim of central sphere and finally turn to bind the sphere with the metallic lobe. e In forming high-order colloidal molecules, P3 overcomes long-range repulsion from bound ligand particles and makes space, before it lands with the dielectric lobe and binds to the metallic lobe. f Plot showing the velocity of patchy particles during the formation of AB2 (red square) and AB6 (blue circle) colloidal molecules, revealing the influence of EHD and dipolar repulsion. g Colloidal molecules with metallic bonds show weak propulsion ability; h Replacing patchy particles with gold spheres enables propulsion of the assembled colloidal molecules. Scale bar: 4 μm.
