Abiotic streamers in a microfluidic system

Abstract

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) beads is introduced into a microfluidic device containing an array of micropillars. PAM and a dilute solution of PS beads are introduced into the microfluidic channel through two separate inlets and localized particle aggregation is found to occur under certain flow regimes. The particle aggregates initially have a string-like morphology and are tethered at their ends to the micropillar walls, while the structure remains suspended in the fluid medium. Such a morphology inspired us to name these structures streamers. The flow regimes under which streamer formation is observed are quantified through state diagrams. We discuss the streamer formation time-scales and also show that streamer formation is likely the result of the flocculation of PS beads. Streamer formation has implications in investigating particle-laden complex flows through porous media.

Investigating fouling at the pore-scale using a microfluidic membrane mimic filtration system

“…Debnath et al . 35 recently demonstrated that particle laden polymeric flows can also lead to morphologically similar structures as bacterial streamers leading to the generalization of the phenomenon to other colloidal systems. When a mixture like particle laden polymer (PAM(0.2%):PS(0.2%) = 1:4) is filtered through our MMM system, a filamentous compliant structure was formed at downstream of the pillars.…”

“…Pore-blockage (inside the pores) is seen when PAM only solution is flown through the MMM device. The PAM molecules have a radius of gyration, R g = 191.9 nm 35 , and their entanglement can completely block the pores during the course of filtration (Fig. 2(b)).…”

“…Debnath et al . 11 named this structure as ‘colloidal streamer’ and this occurs due to synergistic effect resulting from a bridging of PS beads by the polymeric molecules and subsequent adhesion and shearing due to hydrodynamic forces 35 . The attraction between positive PS ( ξ PS ∼ +30 mV at pH 7) and negative PAM molecules ( ξ PAM ∼ −30 mV at pH 7), and the negative PDMS surface ( ξ PDMS ∼ −45 mV at pH 7) caused PAM + PS floc formation and attachment to the surface leading to the streamer fouling at downstream.…”

Mapping the local viscosity of non-Newtonian fluids flowing through disordered porous structures

“…GPV yields flow velocities using sub-resolution tracers similar to micro Particle Image Velocimetry 34 ( ). The tracer particles are added in low concentration to the sample fluid in order to avoid aggregations 35 . The moving particles generate an interference pattern which is advected by the flow (" Methods " section).…”

Effect of microchannel structure and fluid properties on non-inertial particle migration

“…All these studies discussed particle migration in periodic arrays of pillars in Newtonian fluids and there are even fewer studies that study particle migration with non-Newtonian fluids. [16][17][18] Jacob et al 17 investigated the particle dispersion of 2 mm particles in a Newtonian and shear-thinning elastic fluid (HPAM) and they presented an analysis of the influence of elastic instabilities. However, due to the presence of both elasticity and shearthinning properties in HPAM, the effect of each property could not be studied separately.…”