# Energy transfer between colloids via critical interactions

## TL;DR

This study demonstrates how critical Casimir forces near a fluid's critical point can synchronize the motion of colloidal particles and facilitate energy transfer, revealing temperature-dependent collective dynamics.

## Contribution

It provides experimental evidence of temperature-controlled synchronization and energy transfer between colloids mediated by critical Casimir forces near the critical point.

## Key findings

- Synchronization occurs near the critical temperature.
- Critical Casimir forces induce energy transfer between colloids.
- Displacements become uncorrelated far from the critical point.

## Abstract

We report the observation of a temperature-controlled synchronization of two Brownian-particles in a binary mixture close to the critical point of the demixing transition. The two beads are trapped by two optical tweezers whose distance is periodically modulated. We notice that the motion synchronization of the two beads appears when the critical temperature is approached. In contrast, when the fluid is far from its critical temperature, the displacements of the two beads are uncorrelated. Small changes in temperature can radically change the global dynamics of the system. We show that the synchronisation is induced by the critical Casimir forces. Finally, we present the measure of the energy transfers inside the system produced by the critical interaction.