Colloidal molecules with well-controlled bond angles

We present a straightforward technique for the synthesis of asymmetric colloidal molecules with uniform and well-controlled bond angles. The new method makes use of coalescence of liquid protrusions on polystyrene spheres. The bond angle between the seed particles and central sphere can be chosen as desired by adjusting the size of the liquid protrusion. The surprising uniformity of the colloidal molecules comprised of small numbers of seed particles is proven by comparison with 3D models. Considering different origins for this uniformity we conclude that the asymmetric and unique shape is induced by aggregation inside the liquid droplets upon polymerization. This technique offers a new and simple way to make a wide variety of asymmetric colloidal molecules in a reproducible and controlled fashion.