Stochastic dynamics of a Brownian motor based on morphological changes

Abstract

We introduce a simplified model for a microscopic system that performs directed Brownian motion due to coordinated morphological adaptations. This system consists of two spherical particles with adaptable size, that interact through elastic and repulsive forces. We propose an algorithm to control the time dependence of the system's shape that turns it into a Brownian motor, whose stochastic dynamics is analyzed by means of a Langevin model. We restrict ourselves to the simplified case of motors with small shape asymmetries and slow morphological changes, and calculate the average speed at which they should move. We compare the theoretical predictions with the results from Brownian Dynamics simulations and find that they are in very good quantitative agreement. We carry out a comparison of the proposed rectifying algorithm with a classical one based on a ratchet potential and show that in some cases morphological adaptations could produce larger velocities. We thus propose the locomotion mechanism based on controlled structural changes as a novel alternative method from which Brownian motors could operate autonomously, i.e., requiring neither a substrate nor a ratchet field.