The sediment of mixtures of charged colloids: segregation and inhomogeneous electric fields

Abstract

We theoretically study sedimentation-diffusion equilibrium of dilute binary, ternary, and polydisperse mixtures of colloidal particles with different buoyant masses and/or charges. We focus on the low-salt regime, where the entropy of the screening ions drives spontaneous charge separation and the formation of an inhomogeneous macroscopic electric field. The resulting electric force lifts the colloids against gravity, yielding highly nonbarometric and even nonmonotonic colloidal density profiles. The most profound effect is the phenomenon of segregation into layers of colloids with equal mass-per-charge, including the possibility that heavy colloidal species float onto lighter ones.

References in corpus (3)

• Extended sedimentation profiles in charged colloids: the gravitational length, entropy, and electrostatics
• Colloidal brazil nut effect in sediments of binary charged suspensions
• Equilibrium sedimentation profiles of charged colloidal suspensions

Cited by in corpus (7)

• The polydisperse cell model: Non-linear screening and charge renormalization in colloidal mixtures
• A Case Study of Sedimentation of Charged Colloids: The Primitive Model and the Effective One-Component Approach
• Sedimentation of binary mixtures of like- and oppositely charged colloids: the primitive model or effective pair potentials?
• Sedimentation stacking diagrams of binary mixtures of thick and thin hard rods
• Soft repulsive mixtures under gravity: brazil-nut effect, depletion bubbles, boundary layering, nonequilibrium shaking
• Colloidal Brazil nut effect in microswimmer mixtures induced by motility contrast
• Realisation of the Brazil-nut effect in charged colloids without external driving