Flow dynamics through discontinuous clogs of rigid particles in tapered microchannels

Abstract

Suspended particles flowing through complex porous spaces exhibit clogging mechanisms determined by factors including their size, deformability, and the geometry of the confinement. This study describes the clogging of rigid particles in a microfluidic device made up of parallel microchannels that taper from the inlet to the outlet, where the constriction width is approximately equal to the particle size. This converging geometry summarizes the dynamics of clogging in flow channels with constrictions that narrow over multiple length scales. Our novel approach allows the investigation of suspension flow dynamics in confined systems where clogs are formed both by sieving and bridging mechanisms simultaneously. Here, flow tests are conducted at constant driving pressures for different particle volume fractions, and a power-law decay which appears to be peculiar to the channels’ tapered geometry is observed in all cases. Compared to non-tapered channels, the power-law behavior shows flowrate decay is significantly weaker in tapered channels. This weaker flowrate decay is explained by the formation of discontinuous clogs within each channel. Micrographs of the clogged channels reveal clogs do not grow continuously from their initial positions around the channels’ outlet. Rather, new clogs spanning the width of the channel at their points of inception are successively formed as the cake grows toward the inlet area in each microchannel. The results show changes in particle volume fraction at constant driving pressure affect the clogging rate without impacting the underlying dynamics. Unexpectedly, analyses of the particles packing behavior in the microchannels, and post-clogging permeability of the microfluidic devices, reveal the presence of two distinct regimes of driving pressure, though only a small portion of the total device volume and channels surface area are occupied by clogs, regardless of the particle volume fraction. This novel investigation of discontinuous clogging over multiple particle diameters provides unique insights into additional mechanisms to control flow losses in filtration and other confined systems.

Colloid Transport in Bicontinuous Nanoporous Media

“…100−102 This threshold is dependent on various factors, such as the pore-to-colloid size ratio, colloid deformability, geometry of the confinement, environmental temperature, and pressure. 103,104 In our simulations with the specific condition…”

“…In line with previous studies, jamming in colloidal systems is observed only when the colloid volume fraction surpasses a specific threshold, known as the jamming threshold. − This threshold is dependent on various factors, such as the pore-to-colloid size ratio, colloid deformability, geometry of the confinement, environmental temperature, and pressure. , In our simulations with the specific condition ( E c–p = E c–p,3 , E c–c = E c–c,2 , d = 0.30, and Δ P = 15 ε/σ 3 ), we identify the critical threshold for jamming to be around a colloid volume fraction of 0.48. Notably, this threshold slightly lowers when Δ P is increased to 23 ε/σ 3 .…”

Discontinuous clogging in gently tapered microchannels reveals a transient Markov process

“…Flow tests are typically stopped after 1500 s, or when clogs begin to grow into the inlet region connecting all channels, a phenomenon which can be observed by eye. Further, clogs do not move or dislodge during the flow tests [1].…”

Pressure-controlled formation of discontinuous clogs in tapered microchannels

“…The presence of suspended particles in these confined flow systems often results in the formation of clogs, which grow as more suspension flows through the channel 3 . Clog formation causes a decrease in suspension flowrate at constant driving pressures [4][5][6][7] . It can also increase the driving pressure required to maintain a constant flowrate 8 .…”

“…Besides steric effects and surface interactions, channel geometry also significantly impacts the rate and pattern of clogging by suspended particles [31][32][33][34][35] . In pores with parallel walls, clogs grow continuously from their points of inception, leading to a linear decay of flowrate with time 4 . Although increasing the entrance angle of approach to a pore can decrease clogging rates, it does not alter the continuous nature of clog growth 32 .…”