Nonlinear response to probe vitrification


Project Egelhaaf (Düsseldorf)

One and two-component colloidal glasses under mechanically imposed stress


We plan to experimentally investigate the nonlinear response of colloidal glasses to homogeneous and inhomogeneous stress fields. In addition to inhomogeneities in the stress field, such as local forces, distinct particle mobilities (realized by a two-component system) will be studied. The macroscopic stresses and deformations, as well as their transmission through the sample, will be related to changes in the microscopic structure and dynamics on an individual particle level. We will investigate the samples using confocal microscopy, light scattering and rheology while stress is applied. For this purpose a stress-controlled shear cell and indentation device will be constructed.

P2 Laurati/Egelhaaf, Universität Düsseldorf

One and two-component colloidal glasses under shear

We propose to investigate the nonlinear rheology of colloidal glasses, especially two-component
glasses with a large size disparity. Special attention will be devoted to the onset of non-linearity
in both, large-amplitude oscillatory shear (LAOS) and step-shear experiments providing information
on higher harmonics and transient behaviour. Furthermore, the effect of an external
length scale will be probed by investigating bulk and confined samples as well as local perturbations
in indentation experiments. In all situations, the macroscopic response to shear will be
related to the microscopic, structure and dynamics at the particle-level, as observed by confocal
microscopy under shear.