Rheo-NMR and complex fluids: "rapid" velocimetry

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On top of them both, we use these aspects and throw in motion-sensitive tricks of the trade to measure velocities and diffusion in complex fluids undergoing deformational flows.

Historically, the “Rheo-NMR” (Greek /rheos/: flow) lab has explored one particularly fascinating shearing flow scenario, a set of fluid structures known as “worm-like micelles”.  Such structures resemble 1-D curvilinear polymers (on a much larger scale), however, as aggregates of molecules, they are much more free to dissociate and reassemble, leading to interesting mechanical relaxation properties.  Their stress-vs-strain-rate constitutive curve contains an unstable, negatively sloped region, leading to a range of shear rates in which the fluid partitions into high- and low-shear-rate bands, with a potentially fluctuating interface.

Magnetic resonance techniques are inherently slow, which has generally precluded the observation of quickly varying systems.  However, we use image acquisition methods with durations under 50,ms to try and pin down velocity maps within ~100,ms.  In correlation with that, we add spatially resolved NMR to try to understand the interplay between microscopic structure and macroscopic flow, by exploring what is happening on the molecular aggregate scale within each shear-band.

This presentation will cater to a general audience, fear not if you don’t know how MRI really works.  Where fitting, a survey of other projects within the Magnetic Resonance of Materials lab at Victoria University of Wellington will be given.

A talk by Posdoctoral fellow Dr Bradley Douglass, Victoria University of Wellington

Venues

Victoria University of Wellington, AMLT105
University of Otago, please use Scopia Desktop
University of Auckland, Owen G Glen Building, Room 260-321
Massey University, please use Scopia Desktop
Callaghan Innovation – Gracefield Campus, C-Block Meeting Room
University of Canterbury – Psychology 164

If you are unable to attend at one of the above locations the seminar can be viewed via Scopia Desktop

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