Abstract:The increased concern regarding emerging pathogens and antibiotic resistance has drawn interest in the development of rapid and robust microfluidic techniques to analyze microorganisms. The novel parameter known as the electrokinetic equilibrium condition (EEEC) was presented in recent studies, providing an approach to analyze microparticles in microchannels employing unique electrokinetic (EK) signatures. While the EEEC shows great promise, current estimation approaches can be time-consuming or heavily user-d… Show more
“…Presented here are experimental and simulation data demonstrating the effects of EP (3) on electrokinetic injection and particle separation in insulator-based EK (iEK) systems. As recently demonstrated by several research groups [7,8,23,25,33,36,37], the electrophoresis of the second kind (EP (3) ) has a dominant effect on particle electromigration at high electric fields in iEK systems. Explicitly, the nonlinear phenomena of EP (3) must be considered when designing a separation process with an iEK system-those that include an EK injection in particular.…”
Section: Discussionmentioning
confidence: 93%
“…We attribute the high accuracy of the model to the inclusion of EP (3) . Only a handful of reports in the field of microscale EK separations have considered the effects of EP (3) in detail: five recent developments by our group [7,8,23,25,36] and the recent work of Rouhi et al [37] and Tottori et al [33]. Until recently, correction factors [38] were commonly added to mathematical models to improve the accuracy of modeling predictions.…”
Section: Methodsmentioning
confidence: 99%
“…In recent years, there has been significant progress in the development of microscale electrokinetic EK methodologies for the identification, separation, enrichment, analysis, and detection of a wide array of bioparticles, ranging from macromolecules to parasites [3][4][5][6]. Furthermore, EK devices offer the unique potential of being able to exploit both linear and nonlinear EK phenomena [7,8] within the same system, leading to highly selective and discriminatory separation and purification processes [9,10].…”
Section: Introductionmentioning
confidence: 99%
“…The great majority of EK injection schemes have been designed for capillary systems or microchannel systems that do not feature any type of structure within the capillary or the microchannel. The present study was focused on the development of optimized EK injection schemes for direct current insulator-based EK (DC-iEK) systems [7,8]. These are microchannels that contain arrays of insulating structures, and the presence of these structures generates a nonuniform distribution of the electric field when a potential is applied across the channel [21,22].…”
Section: Introductionmentioning
confidence: 99%
“…Particle streaming is particle migration primarily under linear EK effects, and particle trapping is when particle migration is stalled by nonlinear EK effects and bands of trapped particles are formed leading to significant enrichment [24]. The potential of iEK systems is significant, as their applicability for separating and analyzing valuable particles, including protein particles [25], nanovesicles [26], viruses [27], cells [8,28,29], and micro and nanoparticles [30,31], has been fully demonstrated. Given this new knowledge, the present study was focused on designing EK sample injection schemes for DC-iEK systems while considering the effects of nonlinear EP (known as the EP of the second kind or EP (3) ).…”
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.
“…Presented here are experimental and simulation data demonstrating the effects of EP (3) on electrokinetic injection and particle separation in insulator-based EK (iEK) systems. As recently demonstrated by several research groups [7,8,23,25,33,36,37], the electrophoresis of the second kind (EP (3) ) has a dominant effect on particle electromigration at high electric fields in iEK systems. Explicitly, the nonlinear phenomena of EP (3) must be considered when designing a separation process with an iEK system-those that include an EK injection in particular.…”
Section: Discussionmentioning
confidence: 93%
“…We attribute the high accuracy of the model to the inclusion of EP (3) . Only a handful of reports in the field of microscale EK separations have considered the effects of EP (3) in detail: five recent developments by our group [7,8,23,25,36] and the recent work of Rouhi et al [37] and Tottori et al [33]. Until recently, correction factors [38] were commonly added to mathematical models to improve the accuracy of modeling predictions.…”
Section: Methodsmentioning
confidence: 99%
“…In recent years, there has been significant progress in the development of microscale electrokinetic EK methodologies for the identification, separation, enrichment, analysis, and detection of a wide array of bioparticles, ranging from macromolecules to parasites [3][4][5][6]. Furthermore, EK devices offer the unique potential of being able to exploit both linear and nonlinear EK phenomena [7,8] within the same system, leading to highly selective and discriminatory separation and purification processes [9,10].…”
Section: Introductionmentioning
confidence: 99%
“…The great majority of EK injection schemes have been designed for capillary systems or microchannel systems that do not feature any type of structure within the capillary or the microchannel. The present study was focused on the development of optimized EK injection schemes for direct current insulator-based EK (DC-iEK) systems [7,8]. These are microchannels that contain arrays of insulating structures, and the presence of these structures generates a nonuniform distribution of the electric field when a potential is applied across the channel [21,22].…”
Section: Introductionmentioning
confidence: 99%
“…Particle streaming is particle migration primarily under linear EK effects, and particle trapping is when particle migration is stalled by nonlinear EK effects and bands of trapped particles are formed leading to significant enrichment [24]. The potential of iEK systems is significant, as their applicability for separating and analyzing valuable particles, including protein particles [25], nanovesicles [26], viruses [27], cells [8,28,29], and micro and nanoparticles [30,31], has been fully demonstrated. Given this new knowledge, the present study was focused on designing EK sample injection schemes for DC-iEK systems while considering the effects of nonlinear EP (known as the EP of the second kind or EP (3) ).…”
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.
Phages used for phage therapy of multidrug resistant bacteria must be highly purified prior to use. There are limited purification approaches that are broadly applicable to many phage types. Electrokinetics has shown great potential to manipulate phages, but obstructions from the cell debris produced during phage propagation can severely diminish the capacity of an electrokinetic device to concentrate and purify phage samples. A multipart insulator-based electrokinetic device is proposed here to remove the larger, undesirable components of mixtures from phage preparations while transferring the freshly purified and concentrated sample to a second stage for downstream analysis. By combining the large debris prescreen and analysis stages in a streamlined system, this approach simultaneously reduces the impact of clogging and minimizes the sample loss observed during manual transferring of purified samples. Polystyrene particles were used to demonstrate a diminished sample loss of approximately one order of magnitude when using the cascade device as opposed to a manual transfer scheme. The purification and concentration of three different phage samples were demonstrated using the first stage of the cascade device as a prescreen. This design provides a simple method of purifying and concentrating valuable samples from a complex mixture that might impede separation capacity in a single channel.
Insulator‐based dielectrophoresis (iDEP) has been increasingly used for particle manipulation in various microfluidic applications. It exploits insulating structures to constrict and/or curve electric field lines to generate field gradients for particle dielectrophoresis. However, the presence of these insulators, especially those with sharp edges, causes two nonlinear electrokinetic flows, which, if sufficiently strong, may disturb the otherwise linear electrokinetic motion of particles and affect the iDEP performance. One is induced charge electroosmotic (ICEO) flow because of the polarization of the insulators, and the other is electrothermal flow because of the amplified Joule heating in the fluid around the insulators. Both flows vary nonlinearly with the applied electric field (either DC or AC) and exhibit in the form of fluid vortices, which have been utilized to promote some applications while being suppressed in others. The effectiveness of iDEP benefits from a comprehensive understanding of the nonlinear electrokinetic flows, which is complicated by the involvement of the entire iDEP device into electric polarization and thermal diffusion. This article is aimed to review the works on both the fundamentals and applications of ICEO and electrothermal flows in iDEP microdevices. A personal perspective of some future research directions in the field is also given.
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