Thesis
Swimming behaviour of a flagellated alga in Newtonian and complex fluids
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2022
- Thesis identifier
- T16183
- Person Identifier (Local)
- 201772348
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Many microscopic swimmers in nature navigate through complex fluids, such as worm type swimmers in muds, and spermatozoa in cervical mucus. An understanding of the swimming response to such fluids is gaining increasing attention with the hope they will aid in the development of artificial microswimmers and in enhancing processes involving natural bioswimmers, such as fertility treatments. In this work, the swimming behaviour of a swimming green algae, Dunaliella salina, is examined experimentally. Fluids with different rheological properties have been used to study the eects of increasing viscosity, shear thinning properties and viscoelasticity of the surrounding medium on the algae swimming characteristics, such as velocity, beating frequencies and stroke velocities. In a water-like medium akin to their natural environment, the algae were found to swim with a velocity of Vnet = 49:55 µms⁻¹ while beating at a frequency of fBF = 29:97 Hz. With the addition of a viscous enhancing agent (Ficoll PM400) the algae swimming velocity followed an essentially monotonic decrease as viscosity increased, based on a power-law relationship (V x ƞ⁻¹). This was attributed to the constant drag produced by the algae and limited variations in the stroke dynamics, which was confirmed by analysis of the power and recovery strokes. Compared to the Newtonian cases, when the surrounding fluid exhibited shear thinning properties, achieved by addition of Xanthan gum, the swimmer displayed reduced stroke times for comparable displacements in the Newtonian cases. This lead to an overall boost in the recovery stroke over the power stroke. Polyacrylamide was used to analyse the viscoelastic response of the algae. However, for this particular case it was apparent that due to the confounding effects of elasticity and shear thinning, it was difficult to define an elastic response. Furthermore, the wall interactions of Dunaliella salina was quantified, with a preference to bounce from a wall observed. The approach dynamics to the wall were found to hold little influence on the escape, with only a slight tendency for increased reverse bounces at high approach angles and slower velocities.
- Advisor / supervisor
- Oliveira, Mónica Sofia Neves de Freitas
- Haw, Mark
- Resource Type
- DOI
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PDF of thesis T16183 | 2022-03-29 | Público | Descargar |