Offsetting dense particle sedimentation in microfluidic systems
File(s)
Published version
Author(s)
Anyaduba, Dubem
Rodriguez Manzano, Jesus
Type
Journal Article
Abstract
Sedimentation is an undesirable phenomenon that complicates the design of microsystems
that exploit dense microparticles as delivery tools, especially in biotechnological applications. It often
informs the integration of continuous mixing modules, consequently impacting the system footprint,
cost, and complexity. The impact of sedimentation is significantly worse in systems designed with
the intent of particle metering or binary encapsulation in droplets. Circumventing this problem
involves the unsatisfactory adoption of gel microparticles as an alternative. This paper presents two
solutions—a hydrodynamic solution that changes the particle sedimentation trajectory relative to a
flow-rate dependent resultant force, and induced hindered settling (i-HS), which exploits Richardson–
Zaki (RZ) corrections of Stokes’ law. The hydrodynamic solution was validated using a multi-well
fluidic multiplexing and particle metering manifold. Computational image analysis of multiplex
metering efficiency using this method showed an average reduction in well-to-well variation in
particle concentration from 45% (Q = 1 mL/min, n = 32 total wells) to 17% (Q = 10 mL/min, n = 48
total wells). By exploiting a physical property (cloud point) of surfactants in the bead suspension
in vials, the i-HS achieved a 58% reduction in the sedimentation rate. This effect results from the
surfactant phase change, which increases the turbidity (transient increase in particle concentration),
thereby exploiting the RZ theories. Both methods can be used independently or synergistically to
eliminate bead settling in microsystems or to minimize particle sedimentation
that exploit dense microparticles as delivery tools, especially in biotechnological applications. It often
informs the integration of continuous mixing modules, consequently impacting the system footprint,
cost, and complexity. The impact of sedimentation is significantly worse in systems designed with
the intent of particle metering or binary encapsulation in droplets. Circumventing this problem
involves the unsatisfactory adoption of gel microparticles as an alternative. This paper presents two
solutions—a hydrodynamic solution that changes the particle sedimentation trajectory relative to a
flow-rate dependent resultant force, and induced hindered settling (i-HS), which exploits Richardson–
Zaki (RZ) corrections of Stokes’ law. The hydrodynamic solution was validated using a multi-well
fluidic multiplexing and particle metering manifold. Computational image analysis of multiplex
metering efficiency using this method showed an average reduction in well-to-well variation in
particle concentration from 45% (Q = 1 mL/min, n = 32 total wells) to 17% (Q = 10 mL/min, n = 48
total wells). By exploiting a physical property (cloud point) of surfactants in the bead suspension
in vials, the i-HS achieved a 58% reduction in the sedimentation rate. This effect results from the
surfactant phase change, which increases the turbidity (transient increase in particle concentration),
thereby exploiting the RZ theories. Both methods can be used independently or synergistically to
eliminate bead settling in microsystems or to minimize particle sedimentation
Date Issued
2024-09
Date Acceptance
2024-08-21
Citation
Micromachines, 2024, 15 (9)
ISSN
2072-666X
Publisher
MDPI AG
Journal / Book Title
Micromachines
Volume
15
Issue
9
Copyright Statement
© 2024 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
License URL
Identifier
https://www.mdpi.com/2072-666X/15/9/1063
Publication Status
Published
Article Number
1063
Date Publish Online
2024-08-23