Seminar Announcement, 03/10/2015
Levich Institute Seminar Announcement, 03/10/2015
Tuesday, 03/10/2015
2:00 PM
Steinman Hall, Room #312
(Chemical Engineering Conference Room)

Professor Daniel Blair
Georgetown University
Department of Physics

"Applying and Quantifying Shear Deformations in Soft Matter"


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. The flow behavior of a compressed emulsion above its yield point can be characterized by a velocity profile as well as the rearrangement of individual droplets on top of this average motion. We observe that for compressed systems the microscopic dynamics are highly arrested at the highest applied shear rates. I will argue that this is due to a wholesale reconfiguration of the particles into a layered structure. Next, I will present results that utilize boundary stress microscopy to quantify the spatial distribution of surface stresses that arise from sheared in-vitro collagen networks. I will outline our main conclusions which is that the strain stiffening behavior seen in collagen networks can be parameterized by a single characteristic strain and associated stress. This characteristic rheological signature seems to describe both the strain stiffening regime and network yielding.


SM Univ. Chicago (advisors: Jaeger/Nagel)
PhD Clark Univ. (advisor: Arshad Kudrolli)
Post-Doc Harvard Univ. (advisor: Dave Weitz)
2007-- Now Georgetown University (Dept. of Physics/ Institute for Soft Matter)


Structure and mechanical properties of biological and soft materials, including silk, intra- and extra- cellular matrices, emulsions and colloidal dispersions

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