hydrodynamics of microbial filter-feeders

Masters Project Proposal

Abel-John Buchner – May 2018

The three-dimensional hydrodynamics of microbial filter-feeders as a model for bioinspired micromachines

Non-conventional mechanical designs found in nature offer opportunity to develop new bioinspired approaches to engineering problems. Vorticella convallaria, a ciliated sessile protist, is essentially a biological micromachine, and can be used as a model for microscale engineering systems in applications such as actuation or mixing. The organism consists of a bell-shaped head, and a stalk of approximately 100 micron length with which it attaches itself to a substrate. When attached, its ciliary beating creates a flow from which it then filters out bacteria and detritus for consumption. There exist several unresolved issues, for example:

  • Only two-dimensional flow measurements have previously been performed and only in confined quasi-2D domains. Such confinement may be a poor representation filter-feeding hydrodynamics in a relatively unbounded environment [1].
  • On occasion, the stalk rapidly contracts, but the reason and effect of this behaviour is unclear. It has been proposed that it could be a predator avoidance response, or that it could be an attempt to enhance fluid and nutrient mixing.
  • In nature, organisms are not always found in isolation. The hydrodynamic interaction between neighbouring Vorticella therefore has an impact on mixing and nutrient availability.

The aim of this study is to characterise by tomographic particle image velocimetry (PIV) the three-dimensional flow around Vorticella convallaria in relatively unconfined geometries. Thought may be given as to the effect of Vorticella’s contractile behaviour and interactions with neighbours on hydrodynamic mixing and actuation. The project will introduce concepts in advanced optical 3D flow diagnostics and statistical data analysis, as well as basic microbiological culturing techniques.

References:

  1. Pepper, R.E., Roper, M., Ryu, S., Matsudaira, P., Stone, H.A. Nearby boundaries create eddies near microscopic filter feeders. Journal of the Royal Society Interface 2010, 7(46):851-862.
  2. Ryu, S.; Pepper, R.E.; Nagai, M.; France, D.C. Vorticella: A Protozoan for Bio-Inspired Engineering. Micromachines 2017, 8(1):4.
Main anatomical features (A), induced flow due to ciliary action (B), and contractile behaviour (C) of Vorticella convallaria [2].

MSc project in biological fluid mechanics

Chair:
Fluid Mechanics

Involved People:
dr. Abel-John Buchner