Effect of defect location on the swimming speed of a microscopic artificial swimmer: A numerical study

Abstract

The main objective of this work is to explore the effect of defect location on the swimming speed of a microscopic artificial swimmer. The swimmer consists of an artificial filament composed of super-paramagnetic beads connected by elastic linkers and is modeled with a worm-like-chain configuration. To simulate the swimming motion of the filament, a load particle is attached at one end of the filament. The Rotne-Prager approximation is used to evaluate the hydrodynamic interactions between the filament and the fluid. To validate the numerical code, we first simulated the swimming motion of the filament without defect (‘without defect’ means the bending stiffness of the filament is uniform along its length). Next, we simulated the swimming motion of defective filament by setting zero for the bending stiffness value at a particular bead location. We observed that when the location of defect is on the load side of the filament, the swimming velocity is less than that of the defect-less filament, and vice versa. The effect of defect is more significant when it is located on the load side of the filament (The difference between the swimming velocity of defective and defect-less filament amounts to 38%) than when it is on the free end side (The difference is only 7% ). We also observed that at a certain sperm number the swimming direction is reversed when the defect is located very close to the load particle.