Micro-Rheology

Piezo-rheology: Soft matter systems are often rather fragile or only available in small amount. Therefore, methods to probe their mechanical properties must be both sensitive and non-destructive to the architecture of the sample. Two strategies are applied in our group to achieve this: A home-made piezo-rheometer can measure mechanical shear moduli by applying only nanometric deformations to the sample. This greatly reduces shear-induced structural changes to a minimum and is also feasible with small sample quantities. Our design allows performing the rheometric measurements simultaneously to confocal imaging of the sample.
The figure shows a sketch of the piezo-rheometer on the confocal microscope (left) and measurements of a polymer melt at various temperatures.

• Roth, M., M. D’Acunzi, D. Vollmer, and G. K. Auernhammer:
  Viscoelastic rheology of colloid-liquid crystal composites.
  J. Chem. Phys. 132, 124702 (2010).

Indentation and confocal microscopy: We investigate the structural rearrangement in aggregates colloidal systems by combining indentation with confocal microscopy. To do so we measure the 3D coordinates of all particles within the aggregate as well as their individual displacements during the indentation. This information is used to identify reorganization processes and calculate the average strain field.

• Preprint: Roth, M., C. Schilde, P. Lellig, A. Kwade, and G. K. Auernhammer:
  Colloidal aggregates tested via nanoindentation and simultaneous 3D imaging.
  in arXiv:1102.4233v2 [cond-mat.soft] (2011).

Contact: Günter Auernhammer /