Rayleigh−Bénard Instability in Sedimentation

Abstract

Instabilities often arise in the sedimentation of colloidal particles, even when using the density gradient technique. These instabilities occur at volume fractions as low as 10−3 or 10−4, causing mixing of particles throughout the suspension, rather than the smooth sedimentation of particles. Here, we show that the mixing is due to a classical Rayleigh−Bénard instability. The sedimentation process is modeled in an approximate manner, and experiments are done to test whether the approximate model gives maximum stable volume fractions in the correct range. Sedimentation is a well-studied problem, and yet, to our knowledge, this is the first time that the well-known instability has been described in terms of a Rayleigh−Bénard instability.

High-speed, high-purity separation of gold nanoparticle–DNA origami constructs using centrifugation

“…S3 †). 38,39 To demonstrate the separation efficacy of centrifugation, we tested various AuNP-DNA origami constructs using AuNPs with nominal diameters of 5 nm, 10 nm, 15 nm, 20 nm, and 30 nm with actual core-size distributions of the AuNPs measured by transmission electron microscopy (TEM). Fig.…”

“…In the latter case, the precise separation of CNTs according to their electrical and structural properties has been shown. [24][25][26][27] However, until now, the effectiveness of ratezonal centrifugation for the separation of more complex constructs involving heterogeneous nanomaterials has not been demonstrated.…”

Particle-resolved instabilities in colloidal dispersions

“…This review clearly cannot cover all aspects of colloidal instabilities. The following topics are not treated: kinetics of colloidal fluid-fluid phase separation, 20,21 vorticity banding, 22,23 morphological instabilities of a growing interface near a solvent-freezing transition, 24 electro-convection effects, 25 the Rayleigh-Bernard instability 26 and all instabilities that concern the solvent flow, alone.…”

Hydrodynamic Rayleigh-Taylor-like instabilities in sedimenting colloidal mixtures

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