MSE Seminar Series: Daniel Blair
Friday, September 9, 2016
Room 2108, Chemical and Nuclear Engineering Building
Department of Physics
Quantifying Stress Propagation in Sheared Soft Solids
In many cases, soft and biological materials are disordered and have highly heterogeneous microstructure. Therefore, one would expect that the spatial distribution of stresses that are transmitted through these complex materials reflects should reflect the structural heterogeneity. Interestingly, direct quantification of the local stress state of soft materials is largely unknown. Through the combination of rheology and 4D imaging we can directly alter and quantify the connection between microstructure and local stresses. We subject soft and biological materials to precise shear deformations while measuring real space information about the distribution and redistribution of the applied stress. In this talk, I will focus on the flow behavior of two distinct but related disordered materials; flowing colloidal dispersions, and collagen networks. In the colloidal system, I will present experimental and computational results on the dynamical response, at the level of individual particles that directly links the motion and local stress to the bulk rheology. I will also present results that utilize boundary stress microscopy to quantify the spatial distribution of surface stresses that arise from sheared colloids and biopolymer networks. I will outline our main conclusions which are that the strain stiffening behavior observed 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.
About the Speaker
Professor Daniel Blair is an associate professor of physics at Georgetown University and is a founding member of the Institute for Soft Matter Synthesis and Metrology I(SM) 2. Prof. Blair’s group explores the microstructural origins of elasticity in synthetic and biological soft materials.