The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Xiangchun Xuan - One of the best experts on this subject based on the ideXlab platform.
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Joule Heating in Electrokinetic Flow: Theoretical Models
2020Co-Authors: Xiangchun Xuan, Dongqing LiAbstract:Joule Heating is a ubiquitous phenomenon in electrokinetic flow. This internal heat source can lead to significant increase and nonuniformity in liquid temperature. The elevated liquid temperature may on one hand denature live biological samples, while on the other be exploited in heat-related physicochemical processes, for example, the thermal cycling in PCR. Meanwhile, as most liquid properties are temperature sensitive, the induced temperature gradients make the liquid properties nonuniform and thus draw disturbances to the electrokinetic flow of both liquids and species samples [1, 2]. Therefore, it is important to study Joule Heating in electrokinetic flow in order for the optimal design and efficient operation of microfluidic devices. This assay is focused on the theoretical models that describe Joule Heating and its effect on electrokinetic flow in microfluidic channels. We will begin with a summary of the basic methodology including general transport equations. This will be followed by a detailed review of the analytical modeling of Joule Heating in electrokinetic microchannel flows. After that a few key research findings are briefly presented. Finally we suggest some future directions for research on Joule Heating in electrokinetic flow.
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Joule Heating effects on electroosmotic entry flow
Electrophoresis, 2017Co-Authors: Rama Aravind Prabhakaran, Guoqing Hu, Yilong Zhou, Saurin Patel, Akshay Kale, Yongxin Song, Xiangchun XuanAbstract:Electroosmotic flow is the transport method of choice in microfluidic devices over traditional pressure-driven flow. To date, however, studies on electroosmotic flow have been almost entirely limited to inside microchannels. This work presents the first experimental study of Joule Heating effects on electroosmotic fluid entry from the inlet reservoir (i.e., the well that supplies fluids and samples) to the microchannel in a polymer-based microfluidic chip. Electrothermal fluid circulations are observed at the reservoir-microchannel junction, which grow in size and strength with the increasing alternating current to direct current voltage ratio. Moreover, a 2D depth-averaged numerical model is developed to understand the effects of Joule Heating on fluid temperature and flow fields in electrokinetic microfluidic chips. This model overcomes the problems encountered in previous unrealistic 2D and costly 3D models, and is able to predict the observed electroosmotic entry flow patterns with a good agreement.
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Joule Heating effects on reservoir based dielectrophoresis
Electrophoresis, 2014Co-Authors: Akshay Kale, Saurin Patel, Guoqing Hu, Shizhi Qian, Xiangchun XuanAbstract:Reservoir-based dielectrophoresis (rDEP) is a recently developed technique that exploits the inherent electric field gradients at a reservoir-microchannel junction to focus, trap, and sort particles. However, the locally amplified electric field at the junction is likely to induce significant Joule Heating effects that are not considered in previous studies. This work investigates experimentally and numerically these effects on particle transport and control in rDEP processes in PDMS/PDMS microchips. It is found that Joule Heating effects can reduce rDEP focusing considerably and may even disable rDEP trapping. This is caused by the fluid temperature rise at the reservoir-microchannel junction, which significantly increases the local particle velocity due to fluid flow and particle electrophoresis while has a weak impact on the particle velocity due to rDEP. The numerical predictions of particle stream width and electric current, which are the respective indicators of rDEP manipulation and fluid temperature, are demonstrated to both match the experimental measurements with a good accuracy.
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Joule Heating effects on electroosmotic flow in insulator based dielectrophoresis
Electrophoresis, 2011Co-Authors: Sriram Sridharan, Guoqing Hu, Xiangchun XuanAbstract:Insulator-based dielectrophoresis (iDEP) is an emerging technology that has been successfully used to manipulate a variety of particles in microfluidic devices. However, due to the locally amplified electric field around the in-channel insulator, Joule Heating often becomes an unavoidable issue that may disturb the electroosmotic flow and affect the particle motion. This work presents the first experimental study of Joule Heating effects on electroosmotic flow in a typical iDEP device, e. g. a constriction microchannel, under DC-biased AC voltages. A numerical model is also developed to simulate the observed flow pattern by solving the coupled electric, energy, and fluid equations in a simplified two-dimensional geometry. It is observed that depending on the magnitude of the DC voltage, a pair of counter-rotating fluid circulations can occur at either the downstream end alone or each end of the channel constriction. Moreover, the pair at the downstream end appears larger in size than that at the upstream end due to DC electroosmotic flow. These fluid circulations, which are reasonably simulated by the numerical model, form as a result of the action of the electric field on Joule Heating-induced fluid inhomogeneities in the constriction region.
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Joule Heating in electrokinetic flow
Electrophoresis, 2008Co-Authors: Xiangchun XuanAbstract:Electrokinetic flow is an efficient means to manipulate liquids and samples in lab-on-a-chip devices. It has a number of significant advantages over conventional pressure-driven flow. However, there exists inevitable Joule Heating in electrokinetic flow, which is known to cause temperature variations in liquids and draw disturbances to electric, flow and concentration fields via temperature-dependent material properties. Therefore, both the throughput and the resolution of analytic studies performed in microfluidic devices are affected. This article reviews the recent progress on the topic of Joule Heating and its effect in electrokinetic flow, particularly the theoretical and experimental accomplishments from the aspects of fluid mechanics and heat/mass transfer. The primary focus is placed on the temperature-induced flow variations and the accompanying phenomena at the whole channel or chip level.
V Angelopoulos - One of the best experts on this subject based on the ideXlab platform.
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ULF wave electromagnetic energy flux into the ionosphere: Joule Heating implications
Journal of Geophysical Research, 2015Co-Authors: M D Hartinger, M B Moldwin, J W Bonnell, V AngelopoulosAbstract:Ultralow-frequency (ULF) waves—in particular, Alfven waves–transfer energy into the Earth's ionosphere via Joule Heating, but it is unclear how much they contribute to global and local Heating rates relative to other energy sources. In this study we use Time History of Events and Macroscale Interactions during Substorms satellite data to investigate the spatial, frequency, and geomagnetic activity dependence of the ULF wave Poynting vector (electromagnetic energy flux) mapped to the ionosphere. We use these measurements to estimate Joule Heating rates, covering latitudes at or below the nominal auroral oval and below the open/closed field line boundary. We find ULF wave Joule Heating rates (integrated over 3–30 mHz frequency band) typically range from 0.001 to 1 mW/m2. We compare these rates to empirical models of Joule Heating associated with large-scale, static (on ULF wave timescales) current systems, finding that ULF waves nominally contribute little to the global, integrated Joule Heating rate. However, there are extreme cases with ULF wave Joule Heating rates of ≥10 mW/m2—in these cases, which are more likely to occur when Kp ≥ 3, ULF waves make significant contributions to the global Joule Heating rate. We also find ULF waves routinely make significant contributions to local Joule Heating rates near the noon and midnight local time sectors, where static current systems nominally contribute less to Joule Heating; the most important contributions come from lower frequency (
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ulf wave electromagnetic energy flux into the ionosphere Joule Heating implications
Journal of Geophysical Research, 2015Co-Authors: M D Hartinger, M B Moldwin, J W Bonnell, V AngelopoulosAbstract:Ultralow-frequency (ULF) waves—in particular, Alfven waves–transfer energy into the Earth's ionosphere via Joule Heating, but it is unclear how much they contribute to global and local Heating rates relative to other energy sources. In this study we use Time History of Events and Macroscale Interactions during Substorms satellite data to investigate the spatial, frequency, and geomagnetic activity dependence of the ULF wave Poynting vector (electromagnetic energy flux) mapped to the ionosphere. We use these measurements to estimate Joule Heating rates, covering latitudes at or below the nominal auroral oval and below the open/closed field line boundary. We find ULF wave Joule Heating rates (integrated over 3–30 mHz frequency band) typically range from 0.001 to 1 mW/m2. We compare these rates to empirical models of Joule Heating associated with large-scale, static (on ULF wave timescales) current systems, finding that ULF waves nominally contribute little to the global, integrated Joule Heating rate. However, there are extreme cases with ULF wave Joule Heating rates of ≥10 mW/m2—in these cases, which are more likely to occur when Kp ≥ 3, ULF waves make significant contributions to the global Joule Heating rate. We also find ULF waves routinely make significant contributions to local Joule Heating rates near the noon and midnight local time sectors, where static current systems nominally contribute less to Joule Heating; the most important contributions come from lower frequency (<7 mHz) waves.
Dongqing Li - One of the best experts on this subject based on the ideXlab platform.
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Joule Heating in Electrokinetic Flow: Theoretical Models
2020Co-Authors: Xiangchun Xuan, Dongqing LiAbstract:Joule Heating is a ubiquitous phenomenon in electrokinetic flow. This internal heat source can lead to significant increase and nonuniformity in liquid temperature. The elevated liquid temperature may on one hand denature live biological samples, while on the other be exploited in heat-related physicochemical processes, for example, the thermal cycling in PCR. Meanwhile, as most liquid properties are temperature sensitive, the induced temperature gradients make the liquid properties nonuniform and thus draw disturbances to the electrokinetic flow of both liquids and species samples [1, 2]. Therefore, it is important to study Joule Heating in electrokinetic flow in order for the optimal design and efficient operation of microfluidic devices. This assay is focused on the theoretical models that describe Joule Heating and its effect on electrokinetic flow in microfluidic channels. We will begin with a summary of the basic methodology including general transport equations. This will be followed by a detailed review of the analytical modeling of Joule Heating in electrokinetic microchannel flows. After that a few key research findings are briefly presented. Finally we suggest some future directions for research on Joule Heating in electrokinetic flow.
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electrokinetically controlled real time polymerase chain reaction in microchannel using Joule Heating effect
Analytica Chimica Acta, 2006Co-Authors: Guoqing Hu, Dongqing Li, Qing Xiang, Rachel Fu, B Xu, Roberto VendittiAbstract:In this work, a new method to control polymerase chain reaction (PCR) thermal cycling in a microchannel using Joule Heating effect was presented. Joule Heating was generated internally by the current flow through the buffer solution in an electrokinetically-driven microfluidic chip without external heater component. Numerical simulations were developed and conducted to determine the parameters required to achieve the desired thermal cycling. A PDMS-based microchannel PCR chip was fabricated and tested. The power consumption was only 1.3 W for such a Joule Heating-controlled PCR chip. To demonstrate the feasibility of using Joule Heating to control thermal cycling, a DNA fragment of Escherichia coli O157:H7 stx1 was successfully amplified by a two-temperature TaqMan real-time polymerase chain reaction.
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Joule Heating effects on peak broadening in capillary zone electrophoresis
Journal of Micromechanics and Microengineering, 2004Co-Authors: Xiangchun Xuan, Dongqing LiAbstract:Based on Taylor–Aris dispersion theory, a general analytical formula was derived for the theoretical plate height in capillary zone electrophoresis with the consideration of Joule Heating effects. During the electrophoresis, the Joule Heating causes a temperature rise and temperature gradients in the buffer solution. The temperature variations can affect the molecular diffusion, electroosmotic flow and electrophoretic flow via the temperature-dependent diffusion coefficient, dynamic viscosity and electrical conductivity. All these factors contribute to the peak broadening and are considered simultaneously in the present general model. The general formula derived in this paper is employed to discuss quantitatively the peak broadening in the presence of Joule Heating effects. This formula can be easily extended to capillary zone electrophoresis with higher zeta potentials, if an approximate solution to Poisson–Boltzmann equation is employed.
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electroosmotic flow with Joule Heating effects
Lab on a Chip, 2004Co-Authors: Xiangchun Xuan, Bo Xu, David Sinton, Dongqing LiAbstract:Electroosmotic flow with Joule Heating effects was examined numerically and experimentally in this work. We used a fluorescence-based thermometry technique to measure the liquid temperature variation caused by Joule Heating along a micro capillary. We used a caged-fluorescent dye-based microfluidic visualization technique to measure the electroosmotic velocity profile along the capillary. Sharp temperature drops close to the two ends and a high-temperature plateau in the middle of the capillary were observed. Correspondingly, concave–convex–concave velocity profiles were observed in the inlet–middle–outlet regions of a homogeneous capillary. These velocity perturbations were due to the induced pressure gradients resulting from axial variations of temperature. The measured liquid temperature distribution and the electroosmotic velocity profile along the capillary agree well with the predictions of a theoretical model developed in this paper.
Milo S. P. Shaffer - One of the best experts on this subject based on the ideXlab platform.
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Joule Heating characteristics of emulsion-templated graphene aerogels
Advanced Functional Materials, 2015Co-Authors: Robert Menzel, David B. Anthony, Salem M. Bawaked, Shaeel A. Al-thabaiti, Sulaiman N. Basahel, Suelen Barg, Miriam Miranda, Mohamed Mokhtar, Eduardo Saiz, Milo S. P. ShafferAbstract:The Joule Heating properties of an ultralight nanocarbon aerogel are investigated with a view to potential applications as energy-efficient, local gas heater, and other systems. Thermally reduced graphene oxide (rGO) aerogels (10 mg cm−3) with defined shape are produced via emulsion-templating. Relevant material properties, including thermal conductivity, electrical conductivity and porosity, are assessed. Repeatable Joule Heating up to 200 °C at comparatively low voltages (≈1 V) and electrical power inputs (≈2.5 W cm−3) is demonstrated. The steady-state core and surface temperatures are measured, analyzed and compared to analogous two-dimensional nanocarbon film heaters. The assessment of temperature uniformity suggests that heat losses are dominated by conductive and convective heat dissipation at the temperature range studied. The radial temperature gradient of an uninsulated, Joule-heated sample is analyzed to estimate the aerogel's thermal conductivity (around 0.4 W m−1 K−1). Fast initial Joule Heating kinetics and cooling rates (up to 10 K s−1) are exploited for rapid and repeatable temperature cycling, important for potential applications as local gas heaters, in catalysis, and for regenerable of solid adsorbents. These principles may be relevant to wide range of nanocarbon networks and applications.
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Joule Heating characteristics of emulsion templated graphene aerogels
Advanced Functional Materials, 2015Co-Authors: Robert Menzel, David B. Anthony, Salem M. Bawaked, Sulaiman N. Basahel, Suelen Barg, Miriam Miranda, Mohamed Mokhtar, Eduardo Saiz, Shaeel A Althabaiti, Milo S. P. ShafferAbstract:The Joule Heating properties of an ultralight nanocarbon aerogel are investigated with a view to potential applications as energy-efficient, local gas heater, and other systems. Thermally reduced graphene oxide (rGO) aerogels (10 mg cm(-3)) with defined shape are produced via emulsion-templating. Relevant material properties, including thermal conductivity, electrical conductivity and porosity, are assessed. Repeatable Joule Heating up to 200 degrees C at comparatively low voltages (approximate to 1 V) and electrical power inputs (approximate to 2.5 W cm(-3)) is demonstrated. The steady-state core and surface temperatures are measured, analyzed and compared to analogous two-dimensional nanocarbon film heaters. The assessment of temperature uniformity suggests that heat losses are dominated by conductive and convective heat dissipation at the temperature range studied. The radial temperature gradient of an uninsulated, Joule-heated sample is analyzed to estimate the aerogel's thermal conductivity (around 0.4 W m(-1) K-1). Fast initial Joule Heating kinetics and cooling rates (up to 10 K s(-1)) are exploited for rapid and repeatable temperature cycling, important for potential applications as local gas heaters, in catalysis, and for regenerable of solid adsorbents. These principles may be relevant to wide range of nanocarbon networks and applications.
Guoqing Hu - One of the best experts on this subject based on the ideXlab platform.
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Joule Heating effects on electroosmotic entry flow
Electrophoresis, 2017Co-Authors: Rama Aravind Prabhakaran, Guoqing Hu, Yilong Zhou, Saurin Patel, Akshay Kale, Yongxin Song, Xiangchun XuanAbstract:Electroosmotic flow is the transport method of choice in microfluidic devices over traditional pressure-driven flow. To date, however, studies on electroosmotic flow have been almost entirely limited to inside microchannels. This work presents the first experimental study of Joule Heating effects on electroosmotic fluid entry from the inlet reservoir (i.e., the well that supplies fluids and samples) to the microchannel in a polymer-based microfluidic chip. Electrothermal fluid circulations are observed at the reservoir-microchannel junction, which grow in size and strength with the increasing alternating current to direct current voltage ratio. Moreover, a 2D depth-averaged numerical model is developed to understand the effects of Joule Heating on fluid temperature and flow fields in electrokinetic microfluidic chips. This model overcomes the problems encountered in previous unrealistic 2D and costly 3D models, and is able to predict the observed electroosmotic entry flow patterns with a good agreement.
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Joule Heating effects on reservoir based dielectrophoresis
Electrophoresis, 2014Co-Authors: Akshay Kale, Saurin Patel, Guoqing Hu, Shizhi Qian, Xiangchun XuanAbstract:Reservoir-based dielectrophoresis (rDEP) is a recently developed technique that exploits the inherent electric field gradients at a reservoir-microchannel junction to focus, trap, and sort particles. However, the locally amplified electric field at the junction is likely to induce significant Joule Heating effects that are not considered in previous studies. This work investigates experimentally and numerically these effects on particle transport and control in rDEP processes in PDMS/PDMS microchips. It is found that Joule Heating effects can reduce rDEP focusing considerably and may even disable rDEP trapping. This is caused by the fluid temperature rise at the reservoir-microchannel junction, which significantly increases the local particle velocity due to fluid flow and particle electrophoresis while has a weak impact on the particle velocity due to rDEP. The numerical predictions of particle stream width and electric current, which are the respective indicators of rDEP manipulation and fluid temperature, are demonstrated to both match the experimental measurements with a good accuracy.
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Joule Heating effects on electroosmotic flow in insulator based dielectrophoresis
Electrophoresis, 2011Co-Authors: Sriram Sridharan, Guoqing Hu, Xiangchun XuanAbstract:Insulator-based dielectrophoresis (iDEP) is an emerging technology that has been successfully used to manipulate a variety of particles in microfluidic devices. However, due to the locally amplified electric field around the in-channel insulator, Joule Heating often becomes an unavoidable issue that may disturb the electroosmotic flow and affect the particle motion. This work presents the first experimental study of Joule Heating effects on electroosmotic flow in a typical iDEP device, e. g. a constriction microchannel, under DC-biased AC voltages. A numerical model is also developed to simulate the observed flow pattern by solving the coupled electric, energy, and fluid equations in a simplified two-dimensional geometry. It is observed that depending on the magnitude of the DC voltage, a pair of counter-rotating fluid circulations can occur at either the downstream end alone or each end of the channel constriction. Moreover, the pair at the downstream end appears larger in size than that at the upstream end due to DC electroosmotic flow. These fluid circulations, which are reasonably simulated by the numerical model, form as a result of the action of the electric field on Joule Heating-induced fluid inhomogeneities in the constriction region.
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electrokinetically controlled real time polymerase chain reaction in microchannel using Joule Heating effect
Analytica Chimica Acta, 2006Co-Authors: Guoqing Hu, Dongqing Li, Qing Xiang, Rachel Fu, B Xu, Roberto VendittiAbstract:In this work, a new method to control polymerase chain reaction (PCR) thermal cycling in a microchannel using Joule Heating effect was presented. Joule Heating was generated internally by the current flow through the buffer solution in an electrokinetically-driven microfluidic chip without external heater component. Numerical simulations were developed and conducted to determine the parameters required to achieve the desired thermal cycling. A PDMS-based microchannel PCR chip was fabricated and tested. The power consumption was only 1.3 W for such a Joule Heating-controlled PCR chip. To demonstrate the feasibility of using Joule Heating to control thermal cycling, a DNA fragment of Escherichia coli O157:H7 stx1 was successfully amplified by a two-temperature TaqMan real-time polymerase chain reaction.
