The dynamics of a planar beating micro-swimmer constructed using functional fluid

Abstract

The dynamics of a flexible micro-swimmer that contains superparamagnetic beads of different diameter in an oscillating field is studied experimentally. Two types of artificial swimmers are fabricated to determine the flexing characteristics. The effect of key parameters that dominate the motion of the swimmer is determined. The flexibility initially increases linearly with the frequency and reaches a maximum value at a specific frequency. The field intensity has no significant effect on the flexibility when the swimmer is subjected to a higher oscillating frequency. The instantaneous speed of the swimmer increases almost linearly with the flexibility and reaches a maximum value for a swimmer with a specific geometry. On the other hand, the amplitude of the oscillation has a significant effect on swimming effectiveness. The swimmer achieves a maximum instantaneous speed of 1.78 μm/s to 3.16 μm/s when the oscillating amplitude reaches 3.7–4.2 μm. A flexible swimmer with a moderately high amplitude of oscillation generates effective propulsion in an environment with a low Reynolds number of 2.5×10−6–4.5×10−5.

Propulsion Mechanism of Flexible Microbead Swimmers in the Low Reynolds Number Regime

“…All swimmers consisted of different numbers of magnetic microparticles of different sizes. Some previous investigations on the effect of the frequency have shown that a microbead chain or swimmer can be manipulated with a stable structure or efficient movement at a frequency of 7–10 Hz [ 35 , 36 ]. Therefore, all the swimmers were subjected to an oscillating frequency of f = 10 Hz in this study.…”

Propulsion efficiency of achiral microswimmers in viscoelastic polymer fluids

“…Less flexible microbead swimmers can also be assembled in the absence of filaments using the particle's magnetic dipole interactions in a static magnetic field. These swimmers of varying bead diameters achieve nonreciprocal motion because of structural deformation within its cyclic motion 21 . However, the assembled structure of these flexible swimmers are found to be unstable and achieve low propulsion efficiencies 22 .…”

“…These swimmers of varying bead diameters achieve nonreciprocal motion because of structural deformation within its cyclic motion. 21 However, the assembled structure of these flexible swimmers are found to be unstable and achieve low propulsion efficiencies. 22 It has been shown that for non-flexible swimmers, while the shape of an object is essential, the orientation of its transverse magnetic dipole governs swimming.…”