Dip-coating of suspensions

Abstract

Withdrawing a plate from a suspension leads to the entrainment of a coating layer of fluid and particles on the solid surface. In this article, we study the Landau-Levich problem in the case of a suspension of non-Brownian particles at moderate volume fraction $10\%<\varphi <41\%$. We observe different regimes depending on the withdrawal velocity $U$, the volume fraction of the suspension $\varphi$, and the diameter of the particles $2a$. Our results exhibit three coating regimes. (i) At small enough capillary number $Ca$, no particles are entrained, and only a liquid film coats the plate. (ii) At large capillary number, we observe that the thickness of the entrained film of suspension is captured by the Landau-Levich law using the effective viscosity of the suspension $\eta (\varphi )$. (iii) At intermediate capillary numbers, the situation becomes more complicated with a heterogeneous coating on the substrate. We rationalize our experimental findings by providing the domain of existence of these three regimes as a function of the fluid and particles properties.

References in corpus (2)

• Clogging by sieving in microchannels: Application to the detection of contaminants in colloidal suspensions
• Particles accelerate the detachment of viscous liquids

Cited by in corpus (6)

• Spreading and fragmentation of particle-laden liquid sheets
• Capillary filtering of particles during dip coating
• Capillary Sorting of Particles by Dip Coating
• Deposition of a particle-laden film on the inner wall of a tube
• Entrainment of particles during the withdrawal of a fiber from a dilute suspension
• Droplet detachment and pinch-off of bidisperse particulate suspensions