Using a radial flow chamber, we study Saccharomyces cerevisiae, Escherichia coli and Staphylococcus epidermidis kinetics of detachment from stainless steel substrates. Samples of similar surface chemistry, but with different surface topologies are compared: mirror polished and electro-chemically etched. Different grain sizes (20, 40 and 100 microm) and different etching depths (100-650 nm) are tested. Cells are removed from the substrate according to a first-order kinetics defining two macroscopic parameters that depend on the applied stress: the detachment efficiency and the detachment rate constant. Whatever the surface topology, detachment occurs above a threshold and its rate is strongly stimulated by the applied stress. The detachment efficiency is characterized by the shear stress at which half of the cells detach and is independent of surface topology. In contrast, detachment is faster from etched than mirror polished surfaces. Finally, we also show the preferential adhesion of cells to grains of crystallographic orientation with respect to the surface.
