Formation of colloidal molecules induced by alternating-current electric fields

We report a versatile method for building colloidal molecules from particles that are isotropic in geometry and interfacial properties. When an external alternating-current electric field is applied, the particles experience anisotropic interactions that lead to the formation of colloidal oligomers via different assembly pathways that strikingly resemble chemical reactions of real molecules. We propose a mechanism for the formation of colloidal molecules that agrees well with the experiments. Our method can be used to build colloidal analogues of molecules using spherical particles with isotropic properties, which offers considerable advantages over existing methods. Moreover, our approach does not rely on material-specific properties and thus could have potential applications to a broad range of particles with different chemical properties.