Advanced Colloids Experiment - Aging Dynamics and Stress-Relaxation in Colloidal Gels Studied in Microgravity

Colloidal stability is critical to soft matter systems, especially to consumer products. These structures change in time, by processes know as coarsening - meaning the spacing between particles compact. This compaction continually changes this structure. When the structures created in the products can longer resist the gravitational stresses (e.g. buoyancy) on the structures, they collapse. The collapse, such as those that occur in geological formations during earthquakes, is often abrupt and without warning (delayed collapse). This is the essence of product instability. For some systems, the gel collapse can be anticipated by precursors, that can potentially be detected and forecasted.

This research will have significant impacts in two areas:
• It is not clear how the microscopic structure and its dynamics are related to the gel mechanical properties. The structure evolution controls the aging of the gel, and, on earth, this eventually leads to collapse. This work may significantly enhance the knowledge necessary to advance this important area of science.
• Second, relaxation of localized stresses in an amorphous solid brought by a rapid solidification process is ubiquitous in nature and can damage and destroy the materials. Besides affecting the rheological properties of the materials, these dynamics rule the aging of the thermal systems at rest. The detection of failure precursors, as the ones discovered in our colloidal gel, can potentially allow us to forecast the material failure before catastrophic rupture.