Simulation-Based Analysis of the Micropropulsion With Rotating Corkscrew Motion of Flagella

Microorganisms such as ecoli bacterium can propel themselves by means of a corkscrew motion in flow regimes where the Reynolds number is much smaller than one and inertial propulsion methods are ineffective. Micropropulsion with the rotating corkscrew motion of flagella can prove useful as a navigation mechanism for microswimming robots in medical applications. In this work, we present the motion of a microswimmer that consists of an ellipsoid of length two-microns and diameter one micron with a flagellum of length two microns and diameter of 40 nanometers. The microswimmer resembles to a typical ecoli bacterium. We present the effect of parameters such as angular velocity and amplitude of the corkscrew motion. In simulations, time-dependent three-dimensional Navier-Stokes equations are solved in deforming mesh using a commercial package COMSOL. Mesh deformation is specified based on the displacement and rotation of the microswimmer that springs from the net force and torque around the center of mass due to the rotation of the corkscrew-like flagellum. The net linear and angular accelerations of the microswimmer are calculated using ordinary-differential equations that represent the equation of motion, and coupled with the Navier-Stokes equations and the mesh deformation. For simplicity, microswimmer is placed in a cylindrical channel of diameter 20 microns and length 60 microns.