Development of a RheoConfocal Microscope

The macroscopic mechanics of soft solids depends strongly on their microscopic structure and dynamics. Making a direct link between the length scales is a key objective. The MRSEC developed a rheoconfocal instrument, a hybrid between a rheometer and a high-speed spinning-disk confocal microscope; it unites the strengths of both techniques. This allows direct observations of microstructure and dynamics in the in-situ measured mechanical parameters. MRSEC researchers are investigating a long-standing issue in the field of mechanics, namely how the elasticity and mechanical failure of highly heterogeneous materials relates to their specific microscopic geometry. The confocal images at the bottom show how a colloidal gel coarsens during shear flow; rheometry data reveals how the material gradually weakens and becomes more fragile. The results obtained shed new light on the classic problems of structural evolution, fatigue and failure in heterogeneous soft solids.

Harvard MRSEC DMR-0820484 D.A. Weitz and C.M. Friend