CHARACTERIZATION OF TRAJECTORIES OF MAGNETICALLY ACTUATED MICROSWIMMERS WITH HELICAL TAILS

IN CIRCULAR CHANNELS

Hakan Osman Çaldağ
Mechatronics Engineering, MSc. Thesis, 2016

Thesis Jury

Prof. Dr. Serhat Yeşilyurt(Thesis Advisor), Assoc. Prof. Meltem Elitaş, Prof. Dr. Ata Muğan

Date & Time: August 2nd, 2016 –  3:30 PM

Place: FENS G032

Keywords : Microswimmer, Low Reynolds Number Swimming, Computational Fluid Dynamics, Motion in Circular Confinement, Motion Control

Abstract

Micro swimming robots can pave the way for a vast range of applications such as targeted drug delivery, minimally invasive surgery and they can also be used as agents in microsystems. Though it is now possible to manufacture nano-scale swimming structures, motion of these swimmers is yet to be understood in full. Understanding microswimmer motion is crucial in controlling the swimmers. The aim of this thesis is to present an overall picture of trajectory of a microswimmer with a magnetic head and helical tail inside circular channels filled with glycerol. Millimeter long swimmers are produced with 3D printing technology. The swimmers are propelled by a rotating magnetic field achieved by giving alternating current to Helmholtz coil pairs. Effects of confinement, tail length and fluid flow on swimmer trajectory, orientation and propulsion and lateral velocities are reported. It is observed that backward and forward motion of a swimmer result in different trajectories. Amount of confinement affects the way the swimmer follows this trajectory. Fluid flow affects swimming depending on the ratio of tail length to channel size. Direction of fluid flow alters radius of the trajectory. The magnetic field is modulated in order to control the swimmer’s direction of motion. Modulated field can be used to make the swimmer follow a straight trajectory close to the center of the channel. Experimental studies are validated with two computational fluid dynamics (CFD) models; one giving out the average swimming behavior and the other giving full trajectory in a time-dependent fashion.