Geometric optimisation of a micromachine with a spiral tail immersed in viscous medium

Abstract

A model of micromachine with a spiral tail moving in a highly viscous fluid has been simulated using the Boundary Element Method. The trajectory of this micromachine is a straight line and it swims with a velocity close to that of a microorganism with a helical tail. An optimisation process has been carried out in order to find the optimal parameters to obtain the highest translational velocity. The optimum capsule-shaped head of this micromachine has an aspect ratio of about 0.5; the length of the tail is about 8 times the radius of the head, about 4.2 times of its width, and consists of 1.5 wavelengths. The dimensional proportions obtained here are in excellent agreement with previous studies on the motion of microorganisms with helical tails.