Characterising shear-induced dynamics in flowing complex fluids using differential dynamic microscopy

James A. Richards*, Vincent A. Martinez, Jochen Arlt

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Microscopic dynamics reveal the origin of the bulk rheological response in complex fluids. In model systems particle motion can be tracked, but for industrially relevant samples this is often impossible. Here we adapt differential dynamic microscopy (DDM) to study flowing highly-concentrated samples without particle resolution. By combining an investigation of oscillatory flow, using a novel “echo-DDM” analysis, and steady shear, through flow-DDM, we characterise the yielding of a silicone oil emulsion on both the microscopic and bulk level. Through measuring the rate of shear-induced droplet rearrangements and the flow velocity, the transition from a solid-like to liquid-like state is shown to occur in two steps: with droplet mobilisation marking the limit of linear visco-elasticity, followed by the development of shear localisation and macroscopic yielding. Using this suite of techniques, such insight could be developed for a wide variety of challenging complex fluids.
Original languageEnglish
Pages (from-to)8838-8849
Number of pages12
JournalSoft Matter
Issue number39
Early online date17 Sept 2021
Publication statusPublished - 21 Oct 2021


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