School of Engineering
February 2, 2016
Micro-algae hit an obstacle: the role of hydrodynamic and contact forces
Interactions between microorganisms and solid boundaries play an important role in biological processes, like egg fertilization, biofilm formation and soil colonization, where micro-swimmers move within a porous and structured environment. Despite recent efforts to understand their origin, it has not been clear whether these interactions can be understood as fundamentally of hydrodynamic origin or hinging on the swimmer’s direct contact with the boundary. Using a combination of experiments and simulations, we study in detail the interaction of the biflagellate green alga Chlamydomonas reinhardtii, widely used as a model puller microorganism, with straight walls and convex obstacles. Our results reveal that both kinds of forces are crucial for the correct description of the interaction of this class of flagellated microorganisms with boundaries. In particular, we show how the shape of the micro-swimmer influences the scattering dynamics from surfaces.