Determining timescales for directed assembly of particles into bands by shear flow and electric fields

Yee, Andrew; Onuki, Hajime; Tagawa, Yoshiyuki; Yoda, Minami

doi:10.1007/s00348-020-02969-9

Cited by 4 publications

(6 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The band assembly process appears to consist of three stages [5]: Accumulation , where the particles are attracted to and become concentrated at least 100‐fold near the channel wall. Band formation , where the particles assemble into a relatively large number of fairly unstable bands that merge and split. Steady state , where there are a smaller number of bands whose number and spacing remain fairly consistent over time. …”

Section: Introductionmentioning

confidence: 99%

“…Our previous experimental studies have characterized the conditions under which particles assemble into bands as well as band properties and methods to characterize them during the accumulation and steady-state stages [5,6]. These studies used a single type of fluorescent particle but found that the near-wall particle concentration was often too high to discern individual particles.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Near‐wall velocities of particles suspended in shear flow and a streamwise electric field

Yee

Yoda

2022

Electrophoresis

Self Cite

View full text Add to dashboard Cite

Particles with a diameter of ∼0.5 µm in a dilute (volume fractions φ ∞ < 4 × 10 −3 ) suspension assemble into highly elongated structures called "bands" under certain conditions in combined Poiseuille and electroosmotic flows in opposite directions through microchannels at particle-based Reynolds numbers Re p < < 1.The particles are first concentrated near, then form "bands" within ∼6 µm of, the channel wall. The experiments described here examine the near-wall dynamics of individual "tracer" particles during the initial concentration, or accumulation, of particles, and the steady-state stage when the particles have formed relatively stable bands at different near-wall shear rates and electric field magnitudes. Surprisingly, the near-wall upstream particle velocities are found to be consistently greater in magnitude than the expected values based on the particles being convected by the superposition of both flows and subject to electrophoresis, which is in the same direction as the Poiseuille flow. However, the particle velocities scale linearly with the change in electric field magnitude, suggesting that the particle dynamics are dominated by linear electrokinetic phenomena. If this discrepancy with theory is only due to changes in particle electrophoresis, electrophoresis is significantly reduced to values as small as 20%-50% of the Smoluchowski relation, or well below previous model predictions, even for high particle potentials.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Near‐wall velocities of particles suspended in shear flow and a streamwise electric field

Yee

Yoda

2022

Electrophoresis

Self Cite

View full text Add to dashboard Cite

show abstract

“…When the particles lead the flow, which corresponds to the case where the Poiseuille flow and EOFs are in opposite directions, here called "counterflow", the particles, once attracted to and concentrated near the wall, assemble into highly elongated structures that we call "bands" above a minimum electric field magnitude [8]. Subsequent work suggests that this assembly process consists of three stages [9]:…”

Section: Introductionmentioning

confidence: 99%

“…Our group has studied wall‐normal lift forces, suspected to influence wall‐normal particle positions, on a ≈ 0.25 μm particles suspended in the combination of Poiseuille flow driven by a pressure gradient and EOF driven by a voltage gradient, or electric field

\overset{⇀}{E}

in the near‐wall position of a microchannel [6] and also determined that it was possible to form near‐wall streamwise structures called “bands” [7]. More recent studies focus on band characteristics under different particle solution and flow parameters [8, 9].…”

Section: Introductionmentioning

confidence: 99%

“…When the particles lead the flow, which corresponds to the case where the Poiseuille flow and EOFs are in opposite directions, here called “counterflow”, the particles, once attracted to and concentrated near the wall, assemble into highly elongated structures that we call “bands” above a minimum electric field magnitude [8]. Subsequent work suggests that this assembly process consists of three stages [9]: accumulation , where the particles are attracted to and become concentrated near the channel wall; band formation , where the particles assemble into a relatively large number of fairly unstable bands that merge and split; steady‐state , where the band characteristics (average intensity, period) of the bands remain fairly consistent over time. …”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Observations of the near‐wall accumulation of suspended particles due to shear and electroosmotic flow in opposite directions

Yee

Yoda

2021

Electrophoresis

Self Cite

View full text Add to dashboard Cite

On the basis of previous studies, the particles in a dilute (volume fractions φ ∞ < 4 × 10 -3 ) suspension in combined Poiseuille and electroosmotic "counterflow" at flow Reynolds numbers Re ≤ 1 accumulate, then assemble into structures called "bands," within ∼6 μm of the channel wall. The experimental studies presented here use a small fraction of tracer particles labeled with a different fluorophore from the majority "bulk" particles to visualize the dynamics of individual particles in a φ ∞ = 1.7 × 10 -3 suspension. The results at two different near-wall shear rates and three electric field magnitudes E show that the near-wall particles are concentrated about 150-fold when the bands start to form, and are then concentrated about 200-fold to a maximum near-wall volume fraction of ∼0.34. The growth in the near-wall particles during this accumulation stage appears to be exponential. This near-wall particle accumulation is presumably driven by a wallnormal "lift" force. The observations of how the particles accumulate near the wall are compared with recent analyses that predict that suspended particles subject to shear flow and a dc electric field at small particle Reynolds numbers experience such a lift force. A simple model that assumes that the particles are subject to this lift force and Stokes drag suggests that the force driving particles toward the wall, of O(10 -17 N), is consistent with the time scales for particle accumulation observed in the experiments.

show abstract

Interplay of electric field and pressure-driven flow inducing microfluidic particle migration

Abdorahimzadeh

Pratiwi

Vainio

et al. 2023

Chemical Engineering Science

View full text Add to dashboard Cite

Determining timescales for directed assembly of particles into bands by shear flow and electric fields

Cited by 4 publications

References 21 publications

Near‐wall velocities of particles suspended in shear flow and a streamwise electric field

Near‐wall velocities of particles suspended in shear flow and a streamwise electric field

Observations of the near‐wall accumulation of suspended particles due to shear and electroosmotic flow in opposite directions

Interplay of electric field and pressure-driven flow inducing microfluidic particle migration

Contact Info

Product

Resources

About