Recently, the scope of using colloids as model systems has become significantly wider, ambitiously aiming at approaching nature’s complexity. The main key to enable this progress lies in the capability of breaking the isotropy of the interactions by introducing directionality. The simplest way to do so is to produce asymmetric particles with programmable shape and composition. These so-called colloidal molecules can be fabricated through sequential capillary assembly (sCAPA).

(Left) Schematic of the sCAPA working principle. (Right) Examples of colloidal molecules obtained through sCAPA.

After being re-dispersed in water, colloidal molecules can be driven by external magnetic fields, provided that at least one particle in magnetic, or can exhibit self-propulsion on a conductive substrate under an applied AC electric field.

Colloidal molecule rotated by an external magnetic filed at increasing frequency

Active colloidal rotor.

Active circulating colloidal molecules.