title: Nonlinear deformation and localized failure of bacterial streamers in creeping flows.
abstract: We investigate the failure of bacterial floc mediated streamers in a microfluidic device in a creeping flow regime using both experimental observations and analytical modeling. The quantification of streamer deformation and failure behavior is possible due to the use of 200 nm fluorescent polystyrene beads which firmly embed in the extracellular polymeric substance (EPS) and act as tracers. The streamers, which form soon after the commencement of flow begin to deviate from an apparently quiescent fully formed state in spite of steady background flow and limited mass accretion indicating significant mechanical nonlinearity. This nonlinear behavior shows distinct phases of deformation with mutually different characteristic times and comes to an end with a distinct localized failure of the streamer far from the walls. We investigate this deformation and failure behavior for two separate bacterial strains and develop a simplified but nonlinear analytical model describing the experimentally observed instability phenomena assuming a necking route to instability. Our model leads to a power law relation between the critical strain at failure and the fluid velocity scale exhibiting excellent qualitative and quantitative agreeing with the experimental rupture behavior.
authors: Department of Mechanical Engineering, University of Alberta, Edmonton, T6G 2G8, Canada.
authors: Ishita
authors: I
authors: Biswas
authors: Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando FL 32816, USA.
authors: Ranajay
authors: R
authors: Ghosh
authors: Department of Mechanical Engineering, University of Alberta, Edmonton, T6G 2G8, Canada.
authors: Mohtada
authors: M
authors: Sadrzadeh
authors: Department of Mechanical Engineering, University of Alberta, Edmonton, T6G 2G8, Canada.
authors: Aloke
authors: A
authors: Kumar
mesh_terms: D001431:Bacteriological Techniques / Q000295:instrumentation / Q000379:methods; D004129:Dimethylpolysiloxanes; D056656:Lab-On-A-Chip Devices; D018613:Microscopy, Confocal; D009757:Nylons; D011550:Pseudomonas aeruginosa / Q000502:physiology*; D011551:Pseudomonas fluorescens / Q000502:physiology*
chemical_list: D004129:Dimethylpolysiloxanes; D009757:Nylons; C085707:poly(dimethylsiloxane)-polyamide copolymer