Executive Summary : | Over the past two centuries, scientists have been studying heat engines to develop efficient machines. Advancements in miniaturization techniques have led to the development of mesoscopic-scale engines for specific tasks, such as micro-pumping and microflow rectification. These engines also need to efficiently convert energy absorbed from the surrounding environment to work. However, equilibrium thermodynamics cannot be used to understand the mechanism of these engines due to the dominant fluctuations at small length scales. An increasing interest in investigating the energetics and performance of microscopic heat engines has been observed recently, facilitated by the newly developed stochastic thermodynamics. In such studies, stochastic engines realized by colloidal particles confined in harmonic potentials in viscous fluids play a leading role. In a viscous bath, the fluid behaves as an ideal thermostat due to its fast relaxation (~ nanoseconds). However, this fast relaxation does not occur if the surrounding environment is non-Markovian (e.g., viscoelastic). Several exciting behaviors of driven colloidal particles in viscoelastic fluids have been observed due to the strong coupling of the particle with the environment in the presence of a slowly decaying memory. However, very few studies have been carried out towards this crucial direction, and no experiment has ever been done in this crucial direction. This proposal proposes a detailed study of stochastic micro-engines in non-Markovian baths, primarily using optical tweezers. The study will focus on the role of stress relaxation time in the performance of the engines and quantify energetics and non-equilibrium characteristics from the entropy production rate of the system operating in various engine protocols. |