Steering of Magnetic Micro-Swimmers

Abstract

We experimentally investigate the motion of micro-swimmers consisting of several magnetic particles with different sizes. Swimmers are firstly formed by a static unidirectional field, and then manipulated by an additional dynamical perpendicular field. It is known that such magnetic-particle swimmers (or chains) driven by an external field would oscillate with the orientation of the field but lagging behind by a certain phase angle. In this work, we demonstrate if a swimmer subjected to a strong oscillating field which results in an instantaneous phase lag greater than , the swimmer can be steered perpendicularly to its original direction. Detailed swimming mechanism and trajectory are presented. By this innovative steering technology, orientation of a micro-swimmer can be effectively manipulated without a physical reconfiguration of the external field arrangement.

Magnetic microchains and microswimmers in an oscillating magnetic field

“…The experimental method in this present work is mostly the same as what was addressed by Li et al 7,8 Micro-sized magnetic particles are initially dispersed in distilled water. Superparamagnetic particles composed of iron oxide grains (Fe 3 O 4 ) embedded in polystyrene microspheres were used to create linear chains and microswimmers.…”

“…However, rupture in the oscillating chains significantly compromises the swimming efficiency of micro-swimmers. 8 In the worst case, the swimmer may permanently rupture and fail to carry out its mission. This indicates avoiding the structural instability of the chain is an important issue.…”

“…Magnetorheological (MR) suspension is an artificial and smart fluid comprising superparamagnetic solid particles suspended in a nonmagnetic solvent. Because of the superparamagnetism of these microbeads, they can be manipulated by an applied external magnetic field and have been popularly used in microfluidics to design micro devices, such as micromechanical sensors, 1,2 micromixers 3-5 and artificial swimmers, [6][7][8] as well as micro-total-analytical-systems devices, which are tools for biological and biochemical analyses. 9 The distinct behaviors of such magnetic particles are observed under various field configurations, and such different patterns are important issues to their application.…”

“…However, ruptures in the oscillating chains severely decrease the swimming efficiency of microswimmers. 8 To effectively employ an dynamical magnetic micro-bead chain to their potential applications, detailed understandings of the dynamics and behaviors are essential. Therefore, both the computational and experimental investigations into the dynamics of the magnetic microspheres have drawn much attention in recent years.…”

Microfluidic Magnetic Mixing at Low Reynolds Numbers and in Stagnant Fluids

“…If R T > 1, the chain breaks up and possibly reforms. However, this break up and reformation significantly compromises the motion efficiency of oscillating microchains [117]. This means that the chain may rupture and fail to reform again.…”