We look at a zigzag line pattern which frequently appears in during a directionally-drying colloidal dispersions. The pattern has been observed many time in previously works, but never been explained only suggested as “shear band”, based on its which similar to that happen in metals. To investigate the origin of these bands, we use polystyrene and silica dispersions, dried in Hele-Shaw cells, we confirm that these bands are associated with the local shear strains. Moreover, we modify the soft-repulsion force between colloidal particles by adding salt solutions until a critical point bands are vanished.
Another interesting project that we have been working on is the complex phase space of polydisperse colloidal crystals. We are using polydisperse silica colloidal particles and compressed them to reach 15% to 30% of volume fraction. We are using a small-angle X-ray diffraction method to study the coexistence of complex crystal structures and create their phase diagram.