Colloidal particles with a Janus structure are widely sought for applications related to colloidal assembly, stabilization of emulsions, development of active colloids, fabrication of multifunctional devices, as well as diagnosis and treatment of diseases. In this work, we report a versatile route to the fabrication of well-controlled Janus particles by simply breaking the symmetry of spherical particles with swelling. When a polystyrene (PS) sphere covered by a rigid shell made of silica or polydopamine is exposed to a good solvent for PS, a gradually-increased pressure will be created inside the shell. If the pressure becomes high enough to poke a hole in the shell, the spherical symmetry will break while pushing out the swollen PS through the opening to generate a Janus particle comprised of two distinct components. One of the components is made of PS and its size is controlled by the extent of swelling. The other component is comprised of the rigid shell and remaining PS, with its overall diameter determined by the original PS sphere and the rigid shell. This solution-based route holds promises for the scalable production of complex Janus particles with a variety of compositions and in large quantities.

Swelling-induced symmetry breaking: A versatile approach to the fabrication of colloidal particles with a Janus structure

ACS Fall 2021

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