Measurements were the result of multiple sloughing events during each of the experiments. In total, 5 experiments were run using PPF-1 control (no Mg 2+ addition), 4 experiments using PPF-1 with 20 mM MgCl2 added and 1 experiment using PAO1. Average volume (mm 3 ) of biofilm removed from the microchannel during each sloughing event is shown in blue. Statistical significance in shear stress values before and after sloughing events from a pairwise t-test is indicated by *.