Self-assembly and surface rheology of 2D suspension of ellipsoids

The effect of particle shape in two-dimensional suspensions has been investigated using model polystyrene ellipsoids. Optical video microscopy and interfacial rheology, using a range of surface rheometers, were used to study the rheology-structure correlation in these suspensions. For water-air or water-oil interfaces, ellipsoids of the same surface chemistry and size gives rise to either predominantly linear chains or very dense aggregates. This effect is shown to depend on the wetting properties i.e., due to the shift in the three-phase contact line to a position of higher curvature for water-air case. The fundamental building block in these dense networks are triangular clusters, with three ellipsoids connected at their tips. The resulting surface moduli are found to have a power law dependence on surface coverage. It is shown that surface charge, surface coverage and wetting properties can be used effectively to create interfaces with very high surface moduli.