Giant Slip at Liquid-Liquid Interfaces Using Hydrophobic Ball Bearings

Liquid-gas-liquid interfaces stabilized by hydrophobic beads behave as ball bearings under shear and exhibit a giant slip. Using a scaling analysis and molecular dynamics simulations we predict that, when the contact angle $\theta$ between the beads and the liquid is large, the slip length diverges as $R{\rho }^{-1}(\pi -\theta {)}^{-3}$ where $R$ is the bead radius, and $\rho$ is the bead density.

Figure 1

Schematics. (a) Using hydrophobic beads as a ball bearing to enhance liquid-liquid slip. (b) Unit cell of the periodic system analyzed in the text. (c) Expected macroscopic flow in the interface region.

Figure 2

Snapshot of a typical molecular dynamics system (created using VMD [38]), with the associated steady-state velocity profile on the right.

Figure 3

Slip length $b$ as a function of the measured wetting angle $\theta$, using the dynamic definition of the slip length. Data set keys indicate the shear velocity $V$, in LJ units ($\sigma /\tau$). All data sets collapse on a master curve $b\propto (\pi -\theta {)}^{-3}$ (dashed line).