Abiotic streamers in a microfluidic system

In this work, we report the phenomenon of formation of particle aggregates in the form of thin slender strings when a polyacrylamide (PAM) solution, laden with polystyrene (PS) particles is introduced into a microfluidic device containing an array of micropillars. PAM and dilute solution of PS beads is introduced into the microfluidic channel through two separate inlets and localized particle aggregation is found to occur under certain conditions. The particle aggregates initially have a string-like morphology that remain tethered at their ends to the micropillar walls, while the rest of the structure remains suspended in the fluid medium. It is this morphology that inspired us to name these structures streamers. The flow regime under which streamer formation is observed is quantified using through a phase diagram. We discuss the streamer formation time-scales and also show that streamer formation is likely the result of flocculation of the PS beads. These streamers can serve as excellent model systems to study a biological phenomenon by the same name.Comment: 14 PAGES, 6 FIGURE