UC Santa Barbara
Colloidal binary mixtures at fluid-fluid interfaces under steady shear: structural, dynamical and mechanical response
- Author(s): Buttinoni, I
- Zell, ZA
- Squires, TM
- Isa, L
- et al.
Published Web Locationhttps://doi.org/10.1039/c5sm01693b
© The Royal Society of Chemistry. We experimentally study the link between structure, dynamics and mechanical response of two-dimensional (2D) binary mixtures of colloidal microparticles spread at water/oil interfaces. The particles are driven into steady shear by a microdisk forced to rotate at a controlled angular velocity. The flow causes particles to layer into alternating concentric rings of small and big colloids. The formation of such layers is linked to the local, position-dependent shear rate, which triggers two distinct dynamical regimes: particles either move continuously ("Flowing") close to the microdisk, or exhibit intermittent "Hopping" between local energy minima farther away. The shear-rate-dependent surface viscosity of the monolayers can be extracted from a local interfacial stress balance, giving "macroscopic" flow curves whose behavior corresponds to the distinct microscopic regimes of particle motion. Hopping regions reveal a higher resistance to flow compared to the flowing regions, where spatial organization into layers reduces dissipation.
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