A simple method to produce trivalent colloidal particles.

Trivalent patchy colloidal particles are synthesized using a two-step mu-contact printing method. First, one pole of a particle is modified, then the other. With the center portion of the particle left intact, the final chemical makeup consists of three distinct patches of different chemical composition whose relative areas can be controlled. This method depends on preparing stamps with sufficient adhesion to lift off particles yet mild enough adhesion for their subsequent detachment. Furthermore, this method adjusts stamp stiffness, allowing the respective areas of the two printed poles to be controlled separately. To check the efficacy of the method, the shapes of the chemically modified poles were examined using scanning electron microscopy (SEM) after Au nanoparticle adsorption. Fluorescence imaging further confirmed the trivalent patchy particle geometry.