Microscopic thermal machines using run-and-tumble particles

TL;DR

This paper investigates microscopic thermal machines using active run-and-tumble particles, revealing that their efficiency and behavior differ significantly from those using other active particles like AOUP, with potential for high-performance refrigeration under certain protocols.

Contribution

It provides a numerical study of engines and refrigerators with run-and-tumble particles, highlighting the impact of activity type on efficiency and thermodynamic performance.

Findings

Engine efficiency is generally lower than passive engines.

Time-reversed protocols can enhance refrigerator performance.

Coefficient of performance varies non-monotonically with active force.

Abstract

Microscopic thermal machines that are of the dimensions of around few hundred nanometers have been the subject of intense study over the last two decades. Recently, it has been shown that the efficiency of such thermal engines can be enhanced by using active Ornstein-Uhlenbeck particles (AOUP). In this work, we numerically study the behaviour of tiny engines and refrigerators that use an active run-and-tumble particle (RTP) as the working system. We find that the results for the engine mode are in sharp contrast with those of engines using AOUP, thus showing that the nature of activity has a strong influence on the qualitative behaviours of thermal machines for nonequilibrium cycles. The efficiency of an engine using a run-and-tumble particle is found to be smaller in general than a passive microscopic engine. However, when the applied protocol is time-reversed, the resulting microscopic refrigerator can have a much higher coefficient of performance under these conditions. The effect of variation of different parameters of the coefficient of performance has been explored. A non-monotonic variation of coefficient of performance with active force has been found.