# Performance Optimization in Two-dimensional Brownian Rotary Ratchet Models

## TL;DR

This paper presents a method to optimize the performance of 2D Brownian rotary ratchets by adjusting the static potential to maximize angular momentum, velocity, and efficiency, supported by a novel potential design.

## Contribution

It introduces a new ratchet potential form that captures key features of 2D systems and provides a systematic optimization strategy for performance metrics.

## Key findings

- Optimized static potential enhances net rotation and efficiency.
- Design of potential with two closed curves captures essential 2D ratchet features.
- Methodology extends to three-tooth ratchet systems.

## Abstract

With a model for two-dimensional (2D) Brownian rotary ratchets being capable of producing a net torque under athermal random forces, its optimization for mean angular momentum ($L$), mean angular velocity ($\omega$), and efficiency ($\eta$) is considered. In the model, supposing that such a small ratchet system is placed in a thermal bath, the motion of the rotor in the stator is described by the Langevin dynamics of a particle in a 2D ratchet potential, which consists of a static and a time-dependent interaction between rotor and stator; for the latter, we examine a force [randomly directed d.c. field (RDDF)] for which only the direction is instantaneously updated in a sequence of events in a Poisson process. Because of the chirality of the static part of the potential, it is found that the RDDF causes net rotation while coupling with the thermal fluctuations. Then, to maximize the efficiency of the power consumption of the net rotation, we consider optimizing the static part of the ratchet potential. A crucial point is that the newly designed form of ratchet potential enables us to capture the essential feature of 2D ratchet potentials with two closed curves and allows us to systematically construct an optimization strategy. In this paper, we show a method for maximizing $L$, $\omega$, and $\eta$, its outcome in 2D two-tooth ratchet systems, and a direction of optimization for a three-tooth ratchet system.