Impact of tortuous flow on bacteria streamer development in microfluidic system during filtration

Abstract

The way in which bacterial communities colonize flow in porous media is of importance, but basic knowledge on the dynamic of these phenomena is still missing. The aim of this work is to develop microfluidic experiments in order to progress in the understanding of bacteria capture in filters and membranes. PDMS microfluidic devices mimicking filtration processes have been developed to allow a direct dynamic observation of bacteria across 10 or 20 lm width microchannels. When filtered in such devices, bacteria behave surprisingly: Escherichia coli, Pseudomonas aeruginosa or Staphylococcus aureus accumulate in the downstream zone of the filter and form large streamers which oscillate in the flow. In this study, streamer formation is put in evidence for bacteria suspension in non nutritive conditions in less than 1 h. This result is totally different from the one observed in same system with "inert" particles or dead bacteria which are captured in the bottleneck zone and are accumulated in the upstream zone. Observations within different flow geometries (straight channels, connected channels, and staggered row pillars) show that the bacteria streamer development is influenced by the flow configuration and, particularly by the presence of tortuosity within the microchannels zone. These results are discussed at the light of 3D flow simulations. In confined systems and in laminar flow, there is secondary flow (z-velocities) superimposed to the streamwise motion (in xy plane). The presence of the secondary flow in the microsystems has an effect on the bacterial adhesion. A scenario in three steps is established to describe the formation of the streamers and to explain the positive effect of tortuous flow on the development kinetics. V C 2014 AIP Publishing LLC. [http://dx

Bacterial floc mediated rapid streamer formation in creeping flows

“…Bacterial streamers have been observed to form both in high 12 13 , and in low Reynolds number conditions 10 11 14 15 16 . Streamer formation in low Re transport is of significant technological and biomedical interest due to relevance to a wide variety of critical operating scenarios including clogging of biomedical devices such as heart stents, catheters, porous media and water filtration systems 8 11 17 . Rusconi et al 10 , while studying the effect of curved channel geometries using a microfluidic device, found that Pseudomonas aeruginosa formed streamers in the curved sections of the microchannels.…”

Microfluidic Membrane Filtration Systems to Study Biofouling

“…They studied the effect of different pore sizes and dead-end and pseudo cross-flow filtration modes on the biofouling during filtration. In subsequent work, they also reported that pore tortuosity and secondary flows have a significant impact on biofouling formation in the mimic system [33].…”

“…Streamers in a microfluidic system are typically tethered at one end to the pillar walls while the rest of the body is suspended in the downstream direction. Their filamentous structure can extend significantly with the flow [6,33,34].…”

“…Marty et al [33,34] studied the effect of different pore sizes and filtration modes on the lengths of streamers that formed in a microfluidic membrane mimic system. They fabricated a microfluidic device with 25 straight, interconnected and staggered PDMS pillars to observe the nature of biofouling in a membrane mimic.…”

Bacterial biomechanics—From individual behaviors to biofilm and the gut flora

“…The streamers were spatially localized to the middle plane of the curved channel and connected only at the inner curve during each turn, where a secondary vortical flow was observed. The effect of secondary flow on biofilm formation was evaluated by Marty et al (2014) . They discussed the role of secondary flow in streamer formation in three steps.…”