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Abstract

Microswimmers, such as bacteria or motile algae, which typically live in water and soil encounter boundaries very frequently. A wide range of dierent microswimmers seem to spend a signicant amount of time close to such boundaries as opposed to staying in the bulk. Dierent physical mechanisms have been proposed to explain these observations, such as hydrodynamic interactions or steric forces. While hydrodynamics are able to give a good explanation for pusher-type swimmers, its predictions for puller-type swimmers do not explain the trapping at walls. Here the \wall-hugging" eect of puller-type swimmers will be explained. A simple dumbbell model for the cell's shape will be introduced to model the steric wall interactions of Chlamydomonas reinhardtii in a quasi 2d environment. Simulations of this model will be performed and compared with experimental results.