Synergistic action in colloidal heat engines coupled by non-conservative flows

TL;DR

This paper investigates how two colloidal heat engines interact when placed close together, revealing that non-conservative forces influence their collective behavior and can enhance performance, challenging traditional thermodynamic principles.

Contribution

It demonstrates the impact of non-conservative scattering forces on coupled colloidal engines and shows their collective performance surpasses isolated engines.

Findings

Non-conservative forces affect particle motion at close separation.

Coupled engines outperform isolated ones.

Violations of the zeroth law of thermodynamics observed.

Abstract

Collective operation of multiple engines to achieve a common objective is a vital step in the design of complex machines. Recent studies have reduced the length scales of engine design to micro and nanometers. While strategies to build complex machines from these remain to be devised, even the basic design principles remain obscure. Here, we construct and analyze the simplest collection of two engines from a pair of colloidal microspheres in optical traps at close separation. We demonstrate that at such proximity, non-conservative scattering forces that were hitherto neglected, affect the particle motion and hydrodynamics arising from dissipating these results in violating zeroth law of thermodynamics. Leveraging this in a manner analogous to microswimmers and active Brownian particles, we show that a collection of two interacting engines outperform those that are well separated. While these results explore the simplest case of two engines, the underlying concepts could aid in designing larger collections akin to biological systems.