25 research outputs found
Switching Separation Migration Order by Switching Electrokinetic Regime in Electrokinetic Microsystems
Analyte migration order is a major aspect in all migration-based analytical separations methods. Presented here is the manipulation of the migration order of microparticles in an insulator-based electrokinetic separation. Three distinct particle mixtures were studied: a binary mixture of particles with similar electrical charge and different sizes, and two tertiary mixtures of particles of distinct sizes. Each one of the particle mixtures was separated twice, the first separation was performed under low voltage (linear electrokinetic regime) and the second separation was performed under high voltage (nonlinear electrokinetic regime). Linear electrophoresis, which discriminates particles by charge, is the dominant electrokinetic effect in the linear regime; while nonlinear electrophoresis, which discriminates particles by size and shape, is the dominant electrokinetic effect in the nonlinear regime. The separation results obtained with the three particle mixtures illustrated that particle elution order can be changed by switching from the linear electrokinetic regime to the nonlinear electrokinetic regime. Also, in all cases, better separation performances in terms of separation resolution (Rs) were obtained by employing the nonlinear electrokinetic regime allowing nonlinear electrophoresis to be the discriminatory electrokinetic mechanism. These findings could be applied to analyze complex samples containing bioparticles of interest within the micron size range. This is the first report where particle elution order is altered in an iEK system
Fine-Tuning Electrokinetic Injections Considering Nonlinear Electrokinetic Effects in Insulator-Based Devices
The manner of sample injection is critical in microscale electrokinetic (EK) separations, as the resolution of a separation greatly depends on sample quality and how the sample is introduced into the system. There is a significant wealth of knowledge on the development of EK injection methodologies that range from simple and straightforward approaches to sophisticated schemes. The present study focused on the development of optimized EK sample injection schemes for direct current insulator-based EK (DC-iEK) systems. These are microchannels that contain arrays of insulating structures; the presence of these structures creates a nonuniform electric field distribution when a potential is applied, resulting in enhanced nonlinear EK effects. Recently, it was reported that the nonlinear EK effect of electrophoresis of the second kind plays a major role in particle migration in DC-iEK systems. This study presents a methodology for designing EK sample injection schemes that consider the nonlinear EK effects exerted on the particles being injected. Mathematical modeling with COMSOL Multiphysics was employed to identify proper voltages to be used during the EK injection process. Then, a T-microchannel with insulating posts was employed to experimentally perform EK injection and separate a sample containing two types of similar polystyrene particles. The quality of the EK injections was assessed by comparing the resolution (Rs) and number of plates (N) of the experimental particle separations. The findings of this study establish the importance of considering nonlinear EK effects when planning for successful EK injection schemes
Exploiting Particle Mutual Interactions To Enable Challenging Dielectrophoretic Processes
Dielectrophoresis
(DEP) is the motion of particles under the influence
of a nonuniform electric field. In insulator-based dielectrophoresis
(iDEP), the required nonuniform electric fields are generated with
insulating structures embedded in a microchannel. These structures
distort the electric field distribution when an electric potential
is applied. This contribution presents an experimental characterization
of the electrokinetic (EK) and DEP velocities of a set of target particles,
under DC potentials, when additional innocuous particles are used
as fillers. Streak-based particle velocimetry in a tapered channel
was used to assess particle motion. Filler particles of various sizes
were added at different volume fractions (ϕ) to suspending media
containing the target particles/cells. The presence of the filler
particles resulted in electric field distortions and dissimilar particle
behaviors caused by particle–particle interactions. These particle
mutual interactions were exploited to improve the enrichment of low-abundance
yeast cells in an iDEP channel. It was shown that the smallest studied
filler particles (500 nm) have the potential to aid the enrichment
of low-abundance yeast cells when filler volume fractions ∼1
× 10<sup>–5</sup> v/v are used. Enrichment factors of
∼115 were achieved by applying electric potentials as low as
500 V
Separation of Cells and Microparticles in Insulator-Based Electrokinetic Systems
Presented
here is the first continuous separation of microparticles
and cells of similar characteristics employing linear and nonlinear
electrokinetic phenomena in an insulator-based electrokinetic (iEK)
system. By utilizing devices with insulating features, which distort
the electric field distribution, it is possible to combine linear
and nonlinear EK phenomena, resulting in highly effective separation
schemes that leverage the new advancements in nonlinear electrophoresis.
This work combines mathematical modeling and experimentation to separate
four distinct binary mixtures of particles and cells. A computational
model with COMSOL Multiphysics was used to predict the retention times
(tR,p) of the particles and cells in iEK
devices. Then, the experimental separations were carried out using
the conditions identified with the model, where the experimental retention
time (tR,e) of the particles and cells
was measured. A total of four distinct separations of binary mixtures
were performed by increasing the level of difficulty. For the first
separation, two types of polystyrene microparticles, selected to mimic Escherichia coli and Saccharomyces
cerevisiae cells, were separated. By leveraging the
knowledge gathered from the first separation, a mixture of cells of
distinct domains and significant size differences, E. coli and S. cerevisiae, was successfully separated. The third separation also featured
cells of different domains but closer in size: Bacillus
cereus versus S. cerevisiae. The last separation included cells in the same domain and genus, B. cereus versus Bacillus subtilis. Separation results were evaluated in terms of number of plates
(N) and separation resolution (Rs), where Rs values for all
separations were above 1.5, illustrating complete separations. Experimental
results were in agreement with modeling results in terms of retention
times, with deviations in the 6–27% range, while the variation
between repetitions was between 2 and 18%, demonstrating good reproducibility.
This report is the first prediction of the retention time of cells
in iEK systems
Separation of Cells and Microparticles in Insulator-Based Electrokinetic Systems
Presented
here is the first continuous separation of microparticles
and cells of similar characteristics employing linear and nonlinear
electrokinetic phenomena in an insulator-based electrokinetic (iEK)
system. By utilizing devices with insulating features, which distort
the electric field distribution, it is possible to combine linear
and nonlinear EK phenomena, resulting in highly effective separation
schemes that leverage the new advancements in nonlinear electrophoresis.
This work combines mathematical modeling and experimentation to separate
four distinct binary mixtures of particles and cells. A computational
model with COMSOL Multiphysics was used to predict the retention times
(tR,p) of the particles and cells in iEK
devices. Then, the experimental separations were carried out using
the conditions identified with the model, where the experimental retention
time (tR,e) of the particles and cells
was measured. A total of four distinct separations of binary mixtures
were performed by increasing the level of difficulty. For the first
separation, two types of polystyrene microparticles, selected to mimic Escherichia coli and Saccharomyces
cerevisiae cells, were separated. By leveraging the
knowledge gathered from the first separation, a mixture of cells of
distinct domains and significant size differences, E. coli and S. cerevisiae, was successfully separated. The third separation also featured
cells of different domains but closer in size: Bacillus
cereus versus S. cerevisiae. The last separation included cells in the same domain and genus, B. cereus versus Bacillus subtilis. Separation results were evaluated in terms of number of plates
(N) and separation resolution (Rs), where Rs values for all
separations were above 1.5, illustrating complete separations. Experimental
results were in agreement with modeling results in terms of retention
times, with deviations in the 6–27% range, while the variation
between repetitions was between 2 and 18%, demonstrating good reproducibility.
This report is the first prediction of the retention time of cells
in iEK systems
Separation of Cells and Microparticles in Insulator-Based Electrokinetic Systems
Presented
here is the first continuous separation of microparticles
and cells of similar characteristics employing linear and nonlinear
electrokinetic phenomena in an insulator-based electrokinetic (iEK)
system. By utilizing devices with insulating features, which distort
the electric field distribution, it is possible to combine linear
and nonlinear EK phenomena, resulting in highly effective separation
schemes that leverage the new advancements in nonlinear electrophoresis.
This work combines mathematical modeling and experimentation to separate
four distinct binary mixtures of particles and cells. A computational
model with COMSOL Multiphysics was used to predict the retention times
(tR,p) of the particles and cells in iEK
devices. Then, the experimental separations were carried out using
the conditions identified with the model, where the experimental retention
time (tR,e) of the particles and cells
was measured. A total of four distinct separations of binary mixtures
were performed by increasing the level of difficulty. For the first
separation, two types of polystyrene microparticles, selected to mimic Escherichia coli and Saccharomyces
cerevisiae cells, were separated. By leveraging the
knowledge gathered from the first separation, a mixture of cells of
distinct domains and significant size differences, E. coli and S. cerevisiae, was successfully separated. The third separation also featured
cells of different domains but closer in size: Bacillus
cereus versus S. cerevisiae. The last separation included cells in the same domain and genus, B. cereus versus Bacillus subtilis. Separation results were evaluated in terms of number of plates
(N) and separation resolution (Rs), where Rs values for all
separations were above 1.5, illustrating complete separations. Experimental
results were in agreement with modeling results in terms of retention
times, with deviations in the 6–27% range, while the variation
between repetitions was between 2 and 18%, demonstrating good reproducibility.
This report is the first prediction of the retention time of cells
in iEK systems
Separation of Cells and Microparticles in Insulator-Based Electrokinetic Systems
Presented
here is the first continuous separation of microparticles
and cells of similar characteristics employing linear and nonlinear
electrokinetic phenomena in an insulator-based electrokinetic (iEK)
system. By utilizing devices with insulating features, which distort
the electric field distribution, it is possible to combine linear
and nonlinear EK phenomena, resulting in highly effective separation
schemes that leverage the new advancements in nonlinear electrophoresis.
This work combines mathematical modeling and experimentation to separate
four distinct binary mixtures of particles and cells. A computational
model with COMSOL Multiphysics was used to predict the retention times
(tR,p) of the particles and cells in iEK
devices. Then, the experimental separations were carried out using
the conditions identified with the model, where the experimental retention
time (tR,e) of the particles and cells
was measured. A total of four distinct separations of binary mixtures
were performed by increasing the level of difficulty. For the first
separation, two types of polystyrene microparticles, selected to mimic Escherichia coli and Saccharomyces
cerevisiae cells, were separated. By leveraging the
knowledge gathered from the first separation, a mixture of cells of
distinct domains and significant size differences, E. coli and S. cerevisiae, was successfully separated. The third separation also featured
cells of different domains but closer in size: Bacillus
cereus versus S. cerevisiae. The last separation included cells in the same domain and genus, B. cereus versus Bacillus subtilis. Separation results were evaluated in terms of number of plates
(N) and separation resolution (Rs), where Rs values for all
separations were above 1.5, illustrating complete separations. Experimental
results were in agreement with modeling results in terms of retention
times, with deviations in the 6–27% range, while the variation
between repetitions was between 2 and 18%, demonstrating good reproducibility.
This report is the first prediction of the retention time of cells
in iEK systems
Separation of Cells and Microparticles in Insulator-Based Electrokinetic Systems
Presented
here is the first continuous separation of microparticles
and cells of similar characteristics employing linear and nonlinear
electrokinetic phenomena in an insulator-based electrokinetic (iEK)
system. By utilizing devices with insulating features, which distort
the electric field distribution, it is possible to combine linear
and nonlinear EK phenomena, resulting in highly effective separation
schemes that leverage the new advancements in nonlinear electrophoresis.
This work combines mathematical modeling and experimentation to separate
four distinct binary mixtures of particles and cells. A computational
model with COMSOL Multiphysics was used to predict the retention times
(tR,p) of the particles and cells in iEK
devices. Then, the experimental separations were carried out using
the conditions identified with the model, where the experimental retention
time (tR,e) of the particles and cells
was measured. A total of four distinct separations of binary mixtures
were performed by increasing the level of difficulty. For the first
separation, two types of polystyrene microparticles, selected to mimic Escherichia coli and Saccharomyces
cerevisiae cells, were separated. By leveraging the
knowledge gathered from the first separation, a mixture of cells of
distinct domains and significant size differences, E. coli and S. cerevisiae, was successfully separated. The third separation also featured
cells of different domains but closer in size: Bacillus
cereus versus S. cerevisiae. The last separation included cells in the same domain and genus, B. cereus versus Bacillus subtilis. Separation results were evaluated in terms of number of plates
(N) and separation resolution (Rs), where Rs values for all
separations were above 1.5, illustrating complete separations. Experimental
results were in agreement with modeling results in terms of retention
times, with deviations in the 6–27% range, while the variation
between repetitions was between 2 and 18%, demonstrating good reproducibility.
This report is the first prediction of the retention time of cells
in iEK systems