Boosting micromachine studies with Stokesian Dynamics

TL;DR

This paper uses Stokesian Dynamics to analyze the efficiency and dynamics of a simple three-sphere microswimmer, revealing the importance of finite sphere size and stroke type in optimizing microswimmer performance.

Contribution

It provides a detailed hydrodynamic analysis of the three linked spheres swimmer, highlighting the limitations of point-force approximations and emphasizing the role of sphere size and stroke shape.

Findings

Point-force approximation fails at large stroke amplitudes.

Square stroke cycle is more efficient for long arms.

Finite sphere size significantly affects hydrodynamics.

Abstract

Artificial microswimmers, nano and microrobots, are essential in many applications from engineering to biology and medicine. We present a Stokesian Dynamics study of the dynamical properties and efficiency of one of the simplest artificial swimmer, the three linked spheres swimmer (TLS), extensively shown to be an excellent and model example of a deformable micromachine. Results for two different swimming strokes are compared with an approximate solution based on point force interactions. While this approximation accurately reproduces the solutions for swimmers with long arms and strokes of small amplitude, it fails when the amplitude of the stroke is such that the spheres come close together, a condition where indeed the largest efficiencies are obtained. We find that swimmers with a "square stroke cycle" result more efficient than those with "circular stroke cycle" when the swimmer arms are long compared with the sphere radius, but the differences between the two strokes are smaller when the arms of the swimmers are short. This extended theoretical research of TLS incorporates a much precise description of the swimmer hydrodynamics, demonstrating the relevance of considering the finite size of the constitutive microswimmers spheres. This work expects to trigger future innovative steps contributing to the design of micro and nanomachines and its applications.