Personne : Taghavi, Seyed Mohammad
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Université Laval. Département de génie chimique
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- PublicationAccès libreA microfluidic method and custom model for continuous, non-intrusive biofilm viscosity measurements under different nutrient conditions(American Institute of Physics, 2016-11-18) Eslami, Ali; Parvinzadeh Gashti, Mazeyar; Greener, Jesse; Taghavi, Seyed Mohammad; Zarabadi, MirpouyanStraight, low-aspect ratio micro flow cells are used to support biofilm attachment and preferential accumulation at the short side-wall, which progressively reduces the effective channel width. The biofilm shifts downstream at measurable velocities under the imposed force from the constant laminar co-flowing nutrient stream. The dynamic behaviour of the biofilm viscosity is modeled semi-analytically, based on experimental measurements of biofilm dimensions and velocity as inputs. The technique advances the study of biofilm mechanical properties by strongly limiting biases related to non-Newtonian biofilm properties (e.g., shear dependent viscosity) with excellent time resolution. To demonstrate the proof of principle, young Pseudomonas sp. biofilms were analyzed under different nutrient concentrations and constant micro-flow conditions. The striking results show that large initial differences in biofilm viscosities grown under different nutrient concentrations become nearly identical in less than one day, followed by a continuous thickening process. The technique verifies that in 50 h from inoculation to early maturation stages, biofilm viscosity could grow by over 2 orders of magnitude. The approach opens the way for detailed studies of mechanical properties under a wide variety of physiochemical conditions, such as ionic strength, temperature, and shear stress.
- PublicationAccès libreLive-streaming: time-lapse video evidence of novel streamer formation mechanism and varying viscosity(American Institute of Physics, 2015-08-06) Parvinzadeh Gashti, Mazeyar; Greener, Jesse; Bellavance, Julien; Taghavi, Seyed Mohammad; Kroukamp, Otini; Wolfaardt, GideonTime-lapse videos of growing biofilms were analyzed using a background subtraction method, which removed camouflaging effects from the heterogeneous field of view to reveal evidence of streamer formation from optically dense biofilm segments. In addition, quantitative measurements of biofilm velocity and optical density, combined with mathematical modeling, demonstrated that streamer formation occurred from mature, high-viscosity biofilms. We propose a streamer formation mechanism by sudden partial detachment, as opposed to continuous elongation as observed in other microfluidic studies. Additionally, streamer formation occurred in straight microchannels, as opposed to serpentine or pseudo-porous channels, as previously reported.