Description:

Weakly nonlinear excitations are a fundamental characterization technique used in optics, acoustics, heat transfer, and other fields. This talk reviews our contributions to weakly-nonlinear rheology, also called intrinsically-nonlinear or medium-amplitude oscillatory shear (MAOS). We have developed a paradigm of weakly-nonlinear viscoelastic characterization for that has allowed experimental and theoretical advances with implications for microstructure inference and insight with soft matter and complex fluids. This starts with theoretical definitions and first-ever experimental measurements, leading to method development making the method more accessible to the broader community. Application to different soft matter microstructures demonstrates that the weakly-nonlinear regime is a type of "sweet spot," nonlinear enough to provide additional information, but still amenable to theoretical predictions. This is demonstrated with our work on transient polymer networks, polymer melts, soft glassy colloidal suspensions, and capillary suspensions (which exhibit anomalous non-integer power law scaling of the nonlinear stress response with respect to input strain amplitude).

Professor Randy Ewoldt, University of Illinois at Urbana-Champaign

Host: Michelle Driscoll

Keywords: Physics, Astronomy, Complex Systems