# Regensburg 2013 – wissenschaftliches Programm

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# DY: Fachverband Dynamik und Statistische Physik

## DY 23: Statistical Physics in Biological Systems II (joint with BP)

### DY 23.6: Vortrag

### Mittwoch, 13. März 2013, 16:30–16:45, H43

**Optimization of shape for cargo transport with bead-spring microswimmers** — •Jayant Pande and Ana-Sunčana Smith — Cluster of Excellence: EAM, and Institute for Theoretical Physics, Friedrich Alexander University Erlangen-Nürnberg, Germany

Microswimmers are entities that are capable of swimming in fluids at very low Reynolds numbers. A simple model of a microswimmer was introduced by Najafi and Golestanian, and consists of three spheres connected in series by two arms. This model could be used as a basis for constructing cargo-carrying micromachines, with the cargo making up the spheres in the swimmer. To determine whether other shapes for the bodies lead to more efficient swimming, we augment this model by replacing the spheres by general ellipsoids of revolution and including springs between these ellipsoids. The velocities of such three-ellipsoid swimmers acting under the influence of sinusoidal driving forces are calculated, assuming that either the deformations of the arms or the driving forces are known. Comparing the velocities of different swimmers for a given cargo volume leads to a determination of the optimum body shapes and mechanism of propagation. We observe that a rich behaviour for the velocity curve is obtained, depending on the relative magnitudes of the spring constant and the fluid viscosity. The theoretical calculations are supported by simulations using a framework combining "waLBerla", a lattice-Boltzmann method based fluid solver, and "pe", a rigid body physics engine. The simulation results are found to agree well with the calculated values.