In the first experiment, we compared the differences in the biofilm growth rate and structure of P. aeruginosa strains PPF-1 and PAO1. Separate channels were inoculated at the same time (t=0) with an inoculum of either strain. After inoculation, a constant flow of LB 1/10 nutrient solution was passed through both channels. The volumetric flow rate of 0.3 mL•h -1 applied to the initially clean microchannel resulted in a shear stress of 0.37 Pa (Electronic Supplementary Information, Section S2). Imaging was conducted in the next 140 hour period to obtain time-lapse OD maps as biofilms of each strain grew in their respective channel. The full video of the PAO1 and PPF-1 biofilm accumulation and subsequent disruption events is available in the Electronic Supplementary Information (Video S1). Very little changed in the first 20 h, corresponding to a lag phase in which the planktonic bacteria adapted to sessile life on the microchannel walls. After 20 hours, small, separated colonies were observable by microscopy. Initially, OD was nearly zero in both channels, while the CV values were large. Within just a few hours, the CV values for both channels were rapidly reduced as the colonies grew and merged. Both biofilms displayed similar growth rates in the first 40 hours based on the average OD versus time curves (Figures and). In the same time interval, significant differences in appearance were evident (Figure ). A textured surface was initially observed for the PAO1 strain, which is consistent with mushroom-like structures regularly described for PAO1 and other Pseudomonas strains. After the initial formation of mushroom-like structures in PAO1, a process of reticulation occurred, which was clearly visible around 41 hours. This phenomenon was observed but was less obvious for the PPF-1 strain, which tended to produce a biofilm with a less textured topography.