Journal ArticleDOI
Analysis of the Swimming of Microscopic Organisms
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TLDR
In this article, it was shown that if the waves down neighbouring tails are in phase, very much less energy is dissipated in the fluid between them than when the waves are in opposite phase.Abstract:
Large objects which propel themselves in air or water make use of inertia in the surrounding fluid. The propulsive organ pushes the fluid backwards, while the resistance of the body gives the fluid a forward momentum. The forward and backward momenta exactly balance, but the propulsive organ and the resistance can be thought about as acting separately. This conception cannot be transferred to problems of propulsion in microscopic bodies for which the stresses due to viscosity may be many thousands of times as great as those due to inertia. No case of self-propulsion in a viscous fluid due to purely viscous forces seems to have been discussed. The motion of a fluid near a sheet down which waves of lateral displacement are propagated is described. It is found that the sheet moves forwards at a rate 2π 2 b 2 /λ 2 times the velocity of propagation of the waves. Here b is the amplitude and λ the wave-length. This analysis seems to explain how a propulsive tail can move a body through a viscous fluid without relying on reaction due to inertia. The energy dissipation and stress in the tail are also calculated. The work is extended to explore the reaction between the tails of two neighbouring small organisms with propulsive tails. It is found that if the waves down neighbouring tails are in phase very much less energy is dissipated in the fluid between them than when the waves are in opposite phase. It is also found that when the phase of the wave in one tail lags behind that in the other there is a strong reaction, due to the viscous stress in the fluid between them, which tends to force the two wave trains into phase. It is in fact observed that the tails of spermatozoa wave in unison when they are close to one another and pointing the same way.read more
Citations
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Journal ArticleDOI
Physics of microswimmers--single particle motion and collective behavior: a review.
TL;DR: The physics of locomotion of biological and synthetic microswimmers, and the collective behavior of their assemblies, are reviewed and the hydrodynamic aspects of swimming are addressed.
Journal ArticleDOI
Controlled propulsion of artificial magnetic nanostructured propellers.
Ambarish Ghosh,Peer Fischer +1 more
TL;DR: The construction and operation of chiral colloidal propellers that can be navigated in water with micrometer-level precision using homogeneous magnetic fields are reported.
Journal ArticleDOI
The Propulsion of Sea-Urchin Spermatozoa
J. Gray,G. J. Hancock +1 more
TL;DR: Although the amplitude may change as a wave passes along the tail, the propulsive properties of the latter may be expected to be closely similar to those of a tail generating waves of the same average amplitude.
Journal ArticleDOI
Physics of Microswimmers - Single Particle Motion and Collective Behavior
TL;DR: In this article, the authors review the physics of locomotion of biological and synthetic microswimmers, and the collective behavior of their assemblies, including synchronization and the concerted beating of flagella and cilia.
Journal ArticleDOI
Fluid Mechanics of Propulsion by Cilia and Flagella
TL;DR: This review restricts this review primarily to a summary of present understanding of the low-Reynolds-number flows associated with microorganism propulsion and the hydromechanics of ciliary systems.
References
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Journal ArticleDOI
Sea-urchin spermatozoa.
TL;DR: The head of the sea‐urchin spermatozoon is pear‐shaped and axially symmetrical, and the tail, which terminates in an axial fibre, probably contains spiral or coiled structures, as in mammalian spermatozoa.