Tuning the performance of a micrometer-sized Stirling engine through reservoir engineering

Niloyendu Roy,Nathan Leroux,A K Sood,Rajesh Ganapathy

doi:10.1038/s41467-021-25230-1

Abstract

Colloidal heat engines are paradigmatic models to understand the conversion of heat into work in a noisy environment - a domain where biological and synthetic nano/micro machines function. While the operation of these engines across thermal baths is well-understood, how they function across baths with noise statistics that is non-Gaussian and also lacks memory, the simplest departure from the thermal case, remains unclear. Here we quantified the performance of a colloidal Stirling engine operating between an engineered memoryless non-Gaussian bath and a Gaussian one. In the quasistatic limit, the non-Gaussian engine functioned like a thermal one as predicted by theory. On increasing the operating speed, due to the nature of noise statistics, the onset of irreversibility for the non-Gaussian engine preceded its thermal counterpart and thus shifted the operating speed at which power is maximum. The performance of nano/micro machines can be tuned by altering only the nature of reservoir noise statistics.

Highlights

Colloidal heat engines are paradigmatic models to understand the conversion of heat into work in a noisy environment - a domain where biological and synthetic nano/micro machines function
Unlike in thermal baths where the displacement distribution of the colloid, ρ(x), is Gaussian, in active reservoirs, it was nonGaussian and heavy-tailed[13,14]. These rare large displacement events resulted in large work output and the efficiency of this active engine was found to surpass equilibrium engines; even those operating between thermal baths with an infinite temperature difference
A polystyrene colloidal particle of radius R = 2.5 μm suspended in water is held in a harmonic optical potential, U

Summary

Introduction

Colloidal heat engines are paradigmatic models to understand the conversion of heat into work in a noisy environment - a domain where biological and synthetic nano/micro machines function. When the bath noise is non-Gaussian and white, an effective temperature Teff defined through the variance of ρ(x) is thought to act like a bona fide temperature[15,16] and engines operating between such baths are expected to perform like thermal ones in the quasistatic limit. Whether this similarity persists when τ is reduced and irreversibility begins to set in is not known and is worth exploring since real heat engines never operate in the quasistatic limit as here their power P → 0. Gaussian heat baths are yet to be realized and predictions even in the quasistatic limit remain untested

Methods

Results

Conclusion