Colloidal phoresis in odd fluids

Abstract

Under a thermodynamic gradient, for example, the concentration or temperature gradients, the colloidal particles immersed in the solvent can exhibit a directional migration along or against the gradient -- phoresis, a cross transport effect. When the solvent is an odd fluid, where the time-reversal and parity symmetries are broken microscopically, the odd transport phenomenon is allowed. This means an odd phoresis may appear: the colloidal particle migrates perpendicularly to the thermodynamic gradient. Here, we realize the odd diffusiophoresis and odd thermophoresis for a colloidal particle immersed in a two-dimensional odd fluid by performing mesoscale fluid simulations. We further provide the flow field driven by the diffusiophoretic force, which is quantitatively consistent with the numerical solutions of the corresponding odd fluid dynamics equations.

Figures (2)

• Figure 1: The established density/temperature field in simulations. These fields are linear in the far-field and distorted near the colloidal particle. The white lines indicate the isodensity/isotherms lines.
• Figure 2: Flow fields induced by a fixed diffusiophoretic colloidal particle. The background color represents the velocity modulus and the white lines are the flow streamlines. Viscosities used in numerical calculation are predicted by the kinetic theory CSRD: $\eta^{kin}\approx 2.60$, $\eta^{col}\approx 14.46$, $\eta_o^{kin}\approx-1.16$, $\eta_o^{col}\approx 7.80$ for the odd fluid ($\theta=5\pi/9$), and $\eta^{kin}\approx0.40$, $\eta^{col}\approx 23.75$, $\eta_o^{kin}=\eta_o^{col}=0$ for the normal fluid ($\theta=0$).