# Anisotropic thermophoresis

## TL;DR

This paper investigates how elongated colloids respond to temperature gradients, revealing anisotropic thermophoretic forces that depend on orientation and shape, with potential applications in tunable device design.

## Contribution

It demonstrates, through mesoscale simulations, that elongated colloids exhibit orientation-dependent thermophoretic forces, a novel insight into anisotropic thermophoresis.

## Key findings

- Thermophoretic force varies with colloid orientation.
- Elongated colloids show non-zero perpendicular thermophoresis.
- Surface details influence thermophoretic behavior.

## Abstract

Colloidal migration in temperature gradient is referred to as thermophoresis. In contrast to particles with spherical shape, we show that elongated colloids may have a thermophoretic response that varies with the colloid orientation. Remarkably, this can translate into a non-vanishing thermophoretic force in the direction perpendicular to the temperature gradient. Oppositely to the friction force, the thermophoretic force of a rod oriented with the temperature gradient can be larger or smaller than when oriented perpendicular to it. The precise anisotropic thermophoretic behavior clearly depends on the colloidal rod aspect ratio, and also on its surface details, which provides an interesting tunability to the devices constructed based on this principle. By means of mesoscale hydrodynamic simulations, we characterize this effect for different types of rod-like colloids.