# Nanoscale Seebeck effect at hot metal nanostructures

## TL;DR

This paper provides a theoretical analysis of the electrolyte Seebeck effect near heated metal nanostructures, revealing how temperature-induced charge distributions influence electrokinetic phenomena relevant for nanotechnology and colloid science.

## Contribution

It introduces a theoretical framework for understanding the electrolyte Seebeck effect at heated metal surfaces, including the role of polarization charges and ion-specific effects, with implications for thermally driven colloidal motion.

## Key findings

- Thermocharge varies with local temperature, affecting the electric double layer.
- Isopotential condition leads to polarization charge without affecting slip velocity.
- Qualitative agreement with recent experimental observations on Janus colloids.

## Abstract

We theoretically study the electrolyte Seebeck effect in the vicinity of a heated metal nanostructure, such as the cap of an active Janus colloid in an electrolyte, or gold- coated interfaces in optofluidic devices. The thermocharge accumulated at the surface varies with the local temperature, thus modulating the diffuse part of the electric double layer. On a conducting surface with non-uniform temperature, the isopotential condition imposes a significant polarization charge within the metal. Surprisingly, this does not affect the slip velocity, which takes the same value on insulating and conducting surfaces. Our results for specific-ion effects agree qualitatively with recent observations for Janus colloids in different electrolyte solutions. Comparing the thermal, hydrodynamic, and ion diffusion time scales, we expect a rich transient behavior at the onset of thermally powered swimming, extending to microseconds after switching on the heating.