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arXiv · 1504.00166

Interfacial colloidal monolayers under steady shear: structure and flow profiles

Ivo Buttinoni·Zachary A. Zell·Todd M. Squires·Lucio Isa
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Abstract

We study the coupling between the structural dynamics and rheological response of charged colloidal monolayers at water/oil interfaces, driven into steady shear by a microdisk rotating at a controlled angular velocity. The flow causes particles to layer into rotating concentric rings linked to the local, position-dependent shear rate, which triggers two distinct dynamical regimes: particles move continuously "Flowing") close to the microdisk, or exhibit intermittent "Hopping" between local energy minima farther away. The shear-rate dependent surface viscosity of a monolayer can be extracted from an interfacial stress balance, giving "macroscopic" flow curves whose behavior corresponds to the distinct microscopic regimes of particle motion. Hopping Regions correspond to a surface yield stress $\eta \sim \tau_S^Y \dot{\gamma}^{-1}$, whereas Flowing Regions exhibit surface viscosities with power-law shear-thinning characteristics.

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Ivo Buttinoni, Zachary A. Zell, Todd M. Squires, Lucio Isa. 2015-04-01. Interfacial colloidal monolayers under steady shear: structure and flow profiles. https://doi.org/10.1039/c5sm01693b

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