Graduate Research Assistant (Phd Candidate)
Corvallis, Oregon Area
Worked with Dr. Travis Walker to develop a description of macromolecular dynamics in extensional flow fields for the characterization of dilute polymer solutions. The addition of high molecular weight polymer to solvent, even in dilute amounts, can significantly change a fluid’s response to an extensional flow. This behavior is important when formulating models and assessing the ability to print, spray, jet, and spin complex fluids. Generally, macromolecular solutions exhibit large resistance to stretching deformations known as extensional viscosity. For viscous fluids (>20 mPa·s), a capillary breakup extensional rheometer (CaBER) can be used to characterize the extensional relaxation time and transient extensional viscosity of a solution by quantifying the self-thinning of a stretched liquid bridge formed between two parallel plates. Dilute, aqueous solutions, on the other hand, prove challenging to quantify since the time scale of pinch-off is too short for commercial devices, such as the CaBER, to measure. I explored a number of novel techniques, as well as evaluated several previous ideas in an attempt to provide a description of low-viscosity elasticity.Publications:• K.A. Marshall, T.W. Walker. Investigating the dynamics of droplet-breakup in a microfluidic cross-slot device for characterizing the extensional properties of weakly viscoelastic fluids. Rheologica Acta. (2019). • K.A. Marshall, A.M. Liedtke, A.H. Todt, T.W. Walker. Extensional Rheometry with a Handheld Mobile Device. Exp. Fluids. 58, 6 (2017). Presentations: • K.A. Marshall, T.W. Walker. Investigating droplet-breakup dynamics for characterizing low-viscosity elasticity. The XVIIth International Congress on Rheology, Kyoto, Japan. 2016.08.08-13• K.A. Marshall, T.W. Walker. Investigating Droplet-Breakup Dynamics for Characterizing Low-Viscosity Elasticity of Dilute Polymer Solutions. 2016 American Institute of Chemical Engineers Annual Meeting, San Francisco, California. 2016.11.13–18
