Arts & Sciences Events
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Arts & Sciences
[PAST EVENT] Physics Colloquium
April 11, 2014
4pm
Abstract:
Disordered networks of stiff or semi-flexible filaments display unusual mechanical properties, including dramatic stiffening when sheared. Why do these materials differ from ordinary polymeric materials, like rubber or other plastics, which show linear elasticity over a wide range of strains? This talk will provide an overview of the mechanics of polymer networks and introduce the technique of Boundary Stress Microscopy, which adapts the approach of traction force microscopy, normally applied to study forces in living cells, to quantify the non-uniform surface stresses in sheared soft material. Unlike homogeneous continuous solids, some disordered granular materials show heterogeneous propagation of externally applied stresses along localized linear chains. Might similar stress heterogeneity be an important aspect of the mechanics of biopolymer networks? Our measurements on gels of the biopolymer collagen, a major component of the extracellular matrix that provides mechanical support in tissues, show stress variations over length scales much larger than the mesh size of the collagen network. These results show the power of Boundary Stress Microscopy to reveal the nature of stress propagation in disordered soft materials, which is critical for understanding many important mechanical properties, including the ultimate strength of a material and the nature of appropriate microscopic constitutive equations.
Disordered networks of stiff or semi-flexible filaments display unusual mechanical properties, including dramatic stiffening when sheared. Why do these materials differ from ordinary polymeric materials, like rubber or other plastics, which show linear elasticity over a wide range of strains? This talk will provide an overview of the mechanics of polymer networks and introduce the technique of Boundary Stress Microscopy, which adapts the approach of traction force microscopy, normally applied to study forces in living cells, to quantify the non-uniform surface stresses in sheared soft material. Unlike homogeneous continuous solids, some disordered granular materials show heterogeneous propagation of externally applied stresses along localized linear chains. Might similar stress heterogeneity be an important aspect of the mechanics of biopolymer networks? Our measurements on gels of the biopolymer collagen, a major component of the extracellular matrix that provides mechanical support in tissues, show stress variations over length scales much larger than the mesh size of the collagen network. These results show the power of Boundary Stress Microscopy to reveal the nature of stress propagation in disordered soft materials, which is critical for understanding many important mechanical properties, including the ultimate strength of a material and the nature of appropriate microscopic constitutive equations.