Seminars & Colloquia

Applying and Quantifying Forces in Soft Matter

Dan Blair, Georgetown University

Soft and biological materials often exhibit disordered and heterogeneous microstructure. In most cases, the transmission and distribution of stresses through these complex materials reflects their inherent heterogeneity. We are developing a set of techniques that provide the ability to apply to quantify the connection between microstructure and local stresses. We subject soft and biological materials to precise deformations while measuring real space information about the distribution and redistribution of stress. Using our custom confocal rheometer platform we can determine the role of shear stress in a variety of materials. First, we are imaging the redistribution of internal stresses for a sheared compressed emulsion. We extract the distribution of contact forces and correlate those forces to the level of compression and to the magnitude of the strain amplitude. Next we are utilizing a modified version of traction force microscopy to calculate the distribution of forces in sheared in vitro collagen networks. We find that the unique signatures of yielding in these materials follow a universal form.