Buckling Transition in Wall-Bounded Suspension Flows

In this talk we analyze new structural transformations that occur in periodic square arrays of microspheres. During the array evolution, the initial perturbations observed as density waves and vertical particle scatter slowly dissipate and there occurs a sudden transition from the square to hexagonal order with a large number of mobile defects.

The resulting suspension structure resembles a hexatic phase. We explain this transformation in terms of a buckling instability that produces vertical displacements of particle rows. Our simulations predict that at the early stages of the array evolution random transverse particle displacements stabilize the particle lattice, preventing coherent movement of particle rows. We discuss implications of this novel stabilizing mechanism for systems such as compressed membranes undergoing thermal fluctuations.