[Zurück]

I. Gebeshuber, J. Srajer:
"Microfluidic Simulation of a Colonial Diatom Chain Reveals Oscillatory Movement";
in: "Proc. of the 3rd Vienna International Conference Micro- and Nanotechnology - Viennano09", 3rd Vienna International Conference Micro- and Nanotechnology - Viennano09, 2009, ISBN: 978-3-901657-32-0, S. 415 - 420.

Diatoms are single-celled organisms with rigid parts in
relative motion at the micro- and nanometer length
scales. This makes them interesting for nano- and
microtechnological applications [1-6]. Some diatom
species form colonies comprising many cells in form of
long chains [7]. Rutilaria philipinnarum is an example
of such a species. R. philipinnarum is a fossil colonial
diatom thought to have lived in inshore marine waters
[8]. In this species, the single diatoms connect by
linking spines and by a complex siliceous structure
termed the periplekton what can be seen in a simple
drawing in Figure 1. The spines are arranged in an
elliptic way around the periplekton in the middle. On
one hand these structures keep the cells together, but on
the other hand also keep distance between the cells so
that there is still some fluid between the cells. Hence the
shape of the spines allows expansion of the chain to a
certain maximum length and compression to a minimum [4].
Such elaborated linking mechanisms as shown in a
schematic drawing in Figure 1, inspired the question
what would happen to such a diatom colony subjected
to water flow. A diatom chain subjected to fluid flow is
soon being moved as a whole with the flow. However,
in situations where the direction or velocity of flow
changes, the inertia of the whole diatom chain prevents
immediate acceleration according to new flow
conditions. During that situation of acceleration, water
flows through the gaps between the single cells creating
relative motion between the chain and water.
To analyze the problem, the method of Computational
Fluid Dynamics (CFD) is used. CFD is one of the
branches of fluid mechanics that uses numerical
methods and algorithms to solve and analyze problems
that involve fluid flows. The governing equations that
need to be solved consider the conservation of mass,
momentum, pressure and turbulence [9]. Indeed, these
equations are so closely coupled and difficult to solve
that it was not until the advent of modern computers in
the 1960s and 1970s that they could be resolved for real
flow problems within reasonable timescales. A basic
introduction to fluid mechanics for the interested reader
is given by CHORIN and MARSDEN [10]. Numerical
methods used to solve the governing equations in fluid
mechanics can be found in LEVEQUE [11].
The computer simulations presented here shall inspire
biologists working on diatoms to perform experiments
validating the results, and thereby initiate
interdisciplinary research involving groups from
technical and biological backgrounds [12].