Stable cluster phase of Janus particles in two dimensions

A Janus colloidal particle with an attractive hemisphere has three valences, i.e. it can establish three bonds on the hemisphere in two dimensions. With experiments and simulations, we study how the stable cluster phase of the colloids depends on this attraction. With weak attraction, small micellar clusters form, and with strong attraction, these aggregate into linear chains; i.e., a micellar cluster behaves as a unit structure with two valences. Such hierarchical clustering plays a crucial role in the collective behavior of low-valence particles, in particular, for short-range interactions.