The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Jean Berthier - One of the best experts on this subject based on the ideXlab platform.
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Low-cost embossed-paper micro-channels for spontaneous Capillary Flow
Sensors and Actuators B: Chemical, 2017Co-Authors: David Gosselin, B. Joyard-pitiot, J. M. Baumlin, Didier Chaussy, Mohamed Naceur Belgacem, F. Navarro, Jean BerthierAbstract:Hydrophilic porous substrates, in particular paper, are now widely used for the fabrication of microfluidic devices. These materials are very attractive because of their low-cost and their ability to generate Capillary Flow. Such materials avoid the need of external pressure sources or syringe pumps. However, Capillary Flows wicking a hydrophilic fiber matrix experience non-specific adsorption and depend on environmental conditions such as humidity. In this article a novel fabrication method is proposed to create low-cost embossed-paper microfluidic devices allowing for spontaneous Capillary Flow. Thus, embossing is used to design hollow microfluidic channels and chambers on a waterproof and hydrophilic paper surface. Because the hollow-channels obtained are fiber-free, the issues of imbibition are avoided. Besides, the paper surface being hydrophilic, the Capillary Flow in the embossed device is spontaneous. Thus, such microfluidic devices provide an efficient support to perform diagnostics in resource-poor settings. In this work, it is shown that a colorimetric glucose detection can be achieved using embossed-paper channels. The detection is achieved in twelve minutes, either by naked eyes or by analyzing pictures taking with a smartphone camera for quantification.
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Spontaneous Capillary Flow in curved, open microchannels
Microfluidics and Nanofluidics, 2016Co-Authors: Jean Berthier, David Gosselin, Naceur Belgacem, Kenneth A. Brakke, Fabrice Navarro, Didier ChaussyAbstract:Capillary Flows are increasingly used in biotechnology, biology, chemistry, energy and space applications. Motivated by these new developments, designs of Capillary channels have become more sophisticated. In particular, Capillary microsystems often use winding channels for reasons such as compactness, or mixing. The behavior of Capillary microFlows in curved channels is still underdeveloped. In this work, we investigate this type of behavior. In the case of suspended Capillary Flows, is shown that the Flow profile in the curved section is approximately analogous to that in a rectilinear section. In the case of open U-grooves where inner corners are present, the importance of the turn sharpness and of the presence of Capillary filaments is pointed out. For sharp turns, and/or in the presence of precursor Capillary filaments, we found the phenomenon that the inner filament precedes the outer filament in the channel. Analysis of the Capillary Flow in curved channels is performed experimentally using rectangular U-grooves and suspended channels. The experimental observations are compared to Surface Evolver numerical software results.
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Capillary Flow Resistors: Local and Global Resistors
Langmuir, 2016Co-Authors: Jean Berthier, Andrew Pham, Guillaume Delapierre, David Gosselin, Naceur Belgacem, Didier ChaussyAbstract:The use of Capillary systems in space and biotechnology applications requires the regulation of the Capillary Flow velocity. It has been observed that constricted sections act as Flow resistors. In this work, we also show that enlarged sections temporarily reduce the velocity of the Flow. In this work, the theory of the dynamics of Capillary Flows passing through a constricted or an enlarged channel section is presented. It is demonstrated that the physics of a Capillary Flow in a channel with a constriction or an enlargement is different and that a constriction acts as a global Flow resistor and an enlargement as a local Flow resistor. The theoretical results are checked against experimental approaches.
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Viscoelastic Capillary Flow: the case of whole blood
AIMS Press, 2016Co-Authors: David Rabaud, Didier Chaussy, Naceur Belgacem, Jean Berthier, Maxime Huet, Myriam Cubizolles, David GosselinAbstract:The dynamics of spontaneous Capillary Flow of Newtonian fluids is well-known and can be predicted by the Lucas-Washburn-Rideal (LWR) law. However a wide variety of viscoelastic fluids such as alginate, xanthan and blood, does not exhibit the same Newtonian behavior.In this work we consider the Herschel-Bulkley (HB) rheological model and Navier-Stokes equation to derive a generic expression that predicts the Capillary Flow of non-Newtonian fluids. The Herschel-Bulkley rheological model encompasses a wide variety of fluids, including the Power-law fluids (also called Ostwald fluids), the Bingham fluids and the Newtonian fluids. It will be shown that the proposed equation reduces to the Lucas-Washburn-Rideal law for Newtonian fluids and to the Weissenberg-Rabinowitsch-Mooney (WRM) law for power-law fluids. Although HB model cannot reduce to Casson’s law, which is often used to model whole blood rheology, HB model can fit the whole blood rheology with the same accuracy.Our generalized expression for the Capillary Flow of non-Newtonian fluid was used to accurately fit Capillary Flow of whole blood. The Capillary filling of a cylindrical microchannel by whole blood was monitored. The blood first exhibited a Newtonian behavior, then after 7 cm low shear stress and rouleaux formation made LWR fails to fit the data: the blood could not be considered as Newtonian anymore. This non-Newtonian behavior was successfully fit by the proposed equation
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Spontaneous Capillary Flow: Should a Dynamic Contact Angle be Taken into Account ?
2015Co-Authors: Jean Berthier, David Gosselin, Guillaume DelapierreAbstract:Spontaneous Capillary Flow is an interesting solution to move fluids either in microgravity conditions, i.e. in space, or in microfluidic systems, for biotechnology and biology for example. In both cases, gravity is negligible and capillarity becomes the dominant force. Spontaneous Capillary Flow onset, as well as the dynamics of Capillary Flows have been recently documented in the literature for channels of different shapes, confined or open. However, the role of the dynamic contact angle is still unclear. This work aims at bringing a new light on the effect of the dynamic contact angle in the dynamics of Capillary Flows. Copyright © 2015 IFSA Publishing, S. L.
Didier Chaussy - One of the best experts on this subject based on the ideXlab platform.
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Low-cost embossed-paper micro-channels for spontaneous Capillary Flow
Sensors and Actuators B: Chemical, 2017Co-Authors: David Gosselin, B. Joyard-pitiot, J. M. Baumlin, Didier Chaussy, Mohamed Naceur Belgacem, F. Navarro, Jean BerthierAbstract:Hydrophilic porous substrates, in particular paper, are now widely used for the fabrication of microfluidic devices. These materials are very attractive because of their low-cost and their ability to generate Capillary Flow. Such materials avoid the need of external pressure sources or syringe pumps. However, Capillary Flows wicking a hydrophilic fiber matrix experience non-specific adsorption and depend on environmental conditions such as humidity. In this article a novel fabrication method is proposed to create low-cost embossed-paper microfluidic devices allowing for spontaneous Capillary Flow. Thus, embossing is used to design hollow microfluidic channels and chambers on a waterproof and hydrophilic paper surface. Because the hollow-channels obtained are fiber-free, the issues of imbibition are avoided. Besides, the paper surface being hydrophilic, the Capillary Flow in the embossed device is spontaneous. Thus, such microfluidic devices provide an efficient support to perform diagnostics in resource-poor settings. In this work, it is shown that a colorimetric glucose detection can be achieved using embossed-paper channels. The detection is achieved in twelve minutes, either by naked eyes or by analyzing pictures taking with a smartphone camera for quantification.
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Spontaneous Capillary Flow in curved, open microchannels
Microfluidics and Nanofluidics, 2016Co-Authors: Jean Berthier, David Gosselin, Naceur Belgacem, Kenneth A. Brakke, Fabrice Navarro, Didier ChaussyAbstract:Capillary Flows are increasingly used in biotechnology, biology, chemistry, energy and space applications. Motivated by these new developments, designs of Capillary channels have become more sophisticated. In particular, Capillary microsystems often use winding channels for reasons such as compactness, or mixing. The behavior of Capillary microFlows in curved channels is still underdeveloped. In this work, we investigate this type of behavior. In the case of suspended Capillary Flows, is shown that the Flow profile in the curved section is approximately analogous to that in a rectilinear section. In the case of open U-grooves where inner corners are present, the importance of the turn sharpness and of the presence of Capillary filaments is pointed out. For sharp turns, and/or in the presence of precursor Capillary filaments, we found the phenomenon that the inner filament precedes the outer filament in the channel. Analysis of the Capillary Flow in curved channels is performed experimentally using rectangular U-grooves and suspended channels. The experimental observations are compared to Surface Evolver numerical software results.
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Capillary Flow Resistors: Local and Global Resistors
Langmuir, 2016Co-Authors: Jean Berthier, Andrew Pham, Guillaume Delapierre, David Gosselin, Naceur Belgacem, Didier ChaussyAbstract:The use of Capillary systems in space and biotechnology applications requires the regulation of the Capillary Flow velocity. It has been observed that constricted sections act as Flow resistors. In this work, we also show that enlarged sections temporarily reduce the velocity of the Flow. In this work, the theory of the dynamics of Capillary Flows passing through a constricted or an enlarged channel section is presented. It is demonstrated that the physics of a Capillary Flow in a channel with a constriction or an enlargement is different and that a constriction acts as a global Flow resistor and an enlargement as a local Flow resistor. The theoretical results are checked against experimental approaches.
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Viscoelastic Capillary Flow: the case of whole blood
AIMS Press, 2016Co-Authors: David Rabaud, Didier Chaussy, Naceur Belgacem, Jean Berthier, Maxime Huet, Myriam Cubizolles, David GosselinAbstract:The dynamics of spontaneous Capillary Flow of Newtonian fluids is well-known and can be predicted by the Lucas-Washburn-Rideal (LWR) law. However a wide variety of viscoelastic fluids such as alginate, xanthan and blood, does not exhibit the same Newtonian behavior.In this work we consider the Herschel-Bulkley (HB) rheological model and Navier-Stokes equation to derive a generic expression that predicts the Capillary Flow of non-Newtonian fluids. The Herschel-Bulkley rheological model encompasses a wide variety of fluids, including the Power-law fluids (also called Ostwald fluids), the Bingham fluids and the Newtonian fluids. It will be shown that the proposed equation reduces to the Lucas-Washburn-Rideal law for Newtonian fluids and to the Weissenberg-Rabinowitsch-Mooney (WRM) law for power-law fluids. Although HB model cannot reduce to Casson’s law, which is often used to model whole blood rheology, HB model can fit the whole blood rheology with the same accuracy.Our generalized expression for the Capillary Flow of non-Newtonian fluid was used to accurately fit Capillary Flow of whole blood. The Capillary filling of a cylindrical microchannel by whole blood was monitored. The blood first exhibited a Newtonian behavior, then after 7 cm low shear stress and rouleaux formation made LWR fails to fit the data: the blood could not be considered as Newtonian anymore. This non-Newtonian behavior was successfully fit by the proposed equation
David Gosselin - One of the best experts on this subject based on the ideXlab platform.
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Low-cost embossed-paper micro-channels for spontaneous Capillary Flow
Sensors and Actuators B: Chemical, 2017Co-Authors: David Gosselin, B. Joyard-pitiot, J. M. Baumlin, Didier Chaussy, Mohamed Naceur Belgacem, F. Navarro, Jean BerthierAbstract:Hydrophilic porous substrates, in particular paper, are now widely used for the fabrication of microfluidic devices. These materials are very attractive because of their low-cost and their ability to generate Capillary Flow. Such materials avoid the need of external pressure sources or syringe pumps. However, Capillary Flows wicking a hydrophilic fiber matrix experience non-specific adsorption and depend on environmental conditions such as humidity. In this article a novel fabrication method is proposed to create low-cost embossed-paper microfluidic devices allowing for spontaneous Capillary Flow. Thus, embossing is used to design hollow microfluidic channels and chambers on a waterproof and hydrophilic paper surface. Because the hollow-channels obtained are fiber-free, the issues of imbibition are avoided. Besides, the paper surface being hydrophilic, the Capillary Flow in the embossed device is spontaneous. Thus, such microfluidic devices provide an efficient support to perform diagnostics in resource-poor settings. In this work, it is shown that a colorimetric glucose detection can be achieved using embossed-paper channels. The detection is achieved in twelve minutes, either by naked eyes or by analyzing pictures taking with a smartphone camera for quantification.
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Spontaneous Capillary Flow in curved, open microchannels
Microfluidics and Nanofluidics, 2016Co-Authors: Jean Berthier, David Gosselin, Naceur Belgacem, Kenneth A. Brakke, Fabrice Navarro, Didier ChaussyAbstract:Capillary Flows are increasingly used in biotechnology, biology, chemistry, energy and space applications. Motivated by these new developments, designs of Capillary channels have become more sophisticated. In particular, Capillary microsystems often use winding channels for reasons such as compactness, or mixing. The behavior of Capillary microFlows in curved channels is still underdeveloped. In this work, we investigate this type of behavior. In the case of suspended Capillary Flows, is shown that the Flow profile in the curved section is approximately analogous to that in a rectilinear section. In the case of open U-grooves where inner corners are present, the importance of the turn sharpness and of the presence of Capillary filaments is pointed out. For sharp turns, and/or in the presence of precursor Capillary filaments, we found the phenomenon that the inner filament precedes the outer filament in the channel. Analysis of the Capillary Flow in curved channels is performed experimentally using rectangular U-grooves and suspended channels. The experimental observations are compared to Surface Evolver numerical software results.
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Capillary Flow Resistors: Local and Global Resistors
Langmuir, 2016Co-Authors: Jean Berthier, Andrew Pham, Guillaume Delapierre, David Gosselin, Naceur Belgacem, Didier ChaussyAbstract:The use of Capillary systems in space and biotechnology applications requires the regulation of the Capillary Flow velocity. It has been observed that constricted sections act as Flow resistors. In this work, we also show that enlarged sections temporarily reduce the velocity of the Flow. In this work, the theory of the dynamics of Capillary Flows passing through a constricted or an enlarged channel section is presented. It is demonstrated that the physics of a Capillary Flow in a channel with a constriction or an enlargement is different and that a constriction acts as a global Flow resistor and an enlargement as a local Flow resistor. The theoretical results are checked against experimental approaches.
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Viscoelastic Capillary Flow: the case of whole blood
AIMS Press, 2016Co-Authors: David Rabaud, Didier Chaussy, Naceur Belgacem, Jean Berthier, Maxime Huet, Myriam Cubizolles, David GosselinAbstract:The dynamics of spontaneous Capillary Flow of Newtonian fluids is well-known and can be predicted by the Lucas-Washburn-Rideal (LWR) law. However a wide variety of viscoelastic fluids such as alginate, xanthan and blood, does not exhibit the same Newtonian behavior.In this work we consider the Herschel-Bulkley (HB) rheological model and Navier-Stokes equation to derive a generic expression that predicts the Capillary Flow of non-Newtonian fluids. The Herschel-Bulkley rheological model encompasses a wide variety of fluids, including the Power-law fluids (also called Ostwald fluids), the Bingham fluids and the Newtonian fluids. It will be shown that the proposed equation reduces to the Lucas-Washburn-Rideal law for Newtonian fluids and to the Weissenberg-Rabinowitsch-Mooney (WRM) law for power-law fluids. Although HB model cannot reduce to Casson’s law, which is often used to model whole blood rheology, HB model can fit the whole blood rheology with the same accuracy.Our generalized expression for the Capillary Flow of non-Newtonian fluid was used to accurately fit Capillary Flow of whole blood. The Capillary filling of a cylindrical microchannel by whole blood was monitored. The blood first exhibited a Newtonian behavior, then after 7 cm low shear stress and rouleaux formation made LWR fails to fit the data: the blood could not be considered as Newtonian anymore. This non-Newtonian behavior was successfully fit by the proposed equation
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Spontaneous Capillary Flow: Should a Dynamic Contact Angle be Taken into Account ?
2015Co-Authors: Jean Berthier, David Gosselin, Guillaume DelapierreAbstract:Spontaneous Capillary Flow is an interesting solution to move fluids either in microgravity conditions, i.e. in space, or in microfluidic systems, for biotechnology and biology for example. In both cases, gravity is negligible and capillarity becomes the dominant force. Spontaneous Capillary Flow onset, as well as the dynamics of Capillary Flows have been recently documented in the literature for channels of different shapes, confined or open. However, the role of the dynamic contact angle is still unclear. This work aims at bringing a new light on the effect of the dynamic contact angle in the dynamics of Capillary Flows. Copyright © 2015 IFSA Publishing, S. L.
Erik F Hauck - One of the best experts on this subject based on the ideXlab platform.
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Capillary Flow and diameter changes during reperfusion after global cerebral ischemia studied by intravital video microscopy
Journal of Cerebral Blood Flow and Metabolism, 2004Co-Authors: Erik F Hauck, Sebastian Apostel, Julie F Hoffmann, Axel Heimann, Oliver KempskiAbstract:The reaction of cerebral capillaries to ischemia is unclear. Based on Hossmann's observation of postischemic "delayed hypoperfusion," we hypothesized that Capillary Flow is decreased during reperfusion because of increased preCapillary Flow resistance. To test this hypothesis, we measured cerebral Capillary erythrocyte velocity and diameter changes by intravital microscopy in gerbils. A cranial window was prepared over the frontoparietal cortex in 26 gerbils anesthetized with halothane. The animals underwent either a sham operation or fifteen minutes of bilateral carotid artery occlusion causing global cerebral ischemia. Capillary Flow velocities were measured by frame-to-frame tracking of fluorescein isothiocyanate labeled erythrocytes in 1800 capillaries after 1-hour reperfusion. Capillary Flow velocities were decreased compared to control (0.25 +/- 0.27 mm/s vs. 0.76 +/- 0.45 mm/s; P<0.001). PreCapillary arteriole diameters in reperfused animals were reduced to 76.3 +/- 6.9% compared to baseline (P<0.05). Capillary diameters in reperfused animals (2.87 +/- 0.97 microm) were reduced (P<0.001) compared to control (4.08 +/- 1.19 microm). Similar reductions of preCapillary (24%) and Capillary vessel diameters (30%) and absolute Capillary Flow heterogeneity indicate that delayed (Capillary) hypoperfusion occurs as a consequence of increased preCapillary arteriole tone during reperfusion.
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Capillary Flow and diameter changes during reperfusion after global cerebral ischemia studied by intravital video microscopy
Journal of Cerebral Blood Flow and Metabolism, 2004Co-Authors: Erik F Hauck, Sebastian Apostel, Julie F Hoffmann, Axel Heimann, Oliver KempskiAbstract:The reaction of cerebral capillaries to ischemia is unclear. Based on Hossmann's observation of postischemic “delayed hypoperfusion,” we hypothesized that Capillary Flow is decreased during reperfusion because of increased preCapillary Flow resistance. To test this hypothesis, we measured cerebral Capillary erythrocyte velocity and diameter changes by intravital microscopy in gerbils. A cranial window was prepared over the frontoparietal cortex in 26 gerbils anesthetized with halothane. The animals underwent either a sham operation or fifteen minutes of bilateral carotid artery occlusion causing global cerebral ischemia. Capillary Flow velocities were measured by frame-to-frame tracking of fluorescein isothiocyanate labeled erythrocytes in 1800 capillaries after 1-hour reperfusion. Capillary Flow velocities were decreased compared to control (0.25 ± 0.27mm/s vs. 0.76 ± 0.45 mm/s; P < 0.001). PreCapillary arteriole diameters in reperfused animals were reduced to 76.3 ± 6.9% compared to baseline (P < 0.05)....
Satish Kumar - One of the best experts on this subject based on the ideXlab platform.
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Capillary-Flow dynamics in open rectangular microchannels
Journal of Fluid Mechanics, 2021Co-Authors: Panayiotis Kolliopoulos, Krystopher S. Jochem, Daniel C. Johnson, Wieslaw J. Suszynski, Lorraine F. Francis, Satish KumarAbstract:Spontaneous Capillary Flow of liquids in narrow spaces plays a key role in a plethora of applications including lab-on-a-chip devices, heat pipes, propellant management devices in spacecrafts and flexible printed electronics manufacturing. In this work we use a combination of theory and experiment to examine Capillary-Flow dynamics in open rectangular microchannels, which are often found in these applications. Scanning electron microscopy and profilometry are used to highlight the complexity of the free-surface morphology. We develop a self-similar lubrication-theory-based model accounting for this complexity and compare model predictions to those from the widely used modified Lucas–Washburn model, as well as experimental observations over a wide range of channel aspect ratios it fails to account for important axial curvature contributions to the free surface and the agreement worsens. Finally, we show that the lubrication-theory-based model also quantitatively predicts the dynamics of fingers that extend ahead of the meniscus. These findings elucidate the limitations of the modified Lucas–Washburn model and demonstrate the importance of accounting for the effects of complex free-surface morphology on Capillary-Flow dynamics in open rectangular microchannels.
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Capillary Flow with evaporation in open rectangular microchannels
Langmuir, 2019Co-Authors: Panayiotis Kolliopoulos, Krystopher S. Jochem, Lorraine F. Francis, Robert K Lade, Satish KumarAbstract:Numerous applications rely upon Capillary Flow in microchannels for successful operation including lab-on-a-chip devices, porous media Flows, and printed electronics manufacturing. Open microchannels often appear in these applications, and evaporation of the liquid can significantly affect its Flow. In this work, we develop a Lucas-Washburn-type one-dimensional model that incorporates the effects of concentration-dependent viscosity and uniform evaporation on Capillary Flow in channels of a rectangular cross section. The model yields predictions of the time evolution of the liquid front down the length of the microchannel. For the case where evaporation is absent, prior studies have demonstrated better agreement between model predictions and experimental observations in low-viscosity liquids when using a no-slip rather than a no-stress boundary condition at the upper liquid-air interface. However, Flow visualization experiments conducted in this work suggest the absence of a rigidified liquid-air interface. The use of the no-stress condition results in overestimation of the time evolution of the liquid front, which appears to be due to underestimation of the viscous forces from (i) the upper and front meniscus morphology, (ii) dynamic contact angle effects, and (iii) surface roughness, none of which are accounted for in the model. When high-viscosity liquids are considered, the large bulk viscosity is found to suppress these factors, resulting in better agreement between model predictions using the no-stress condition and experiments. Model predictions are also compared to prior experiments involving poly(vinyl alcohol) in the presence of evaporation by using the evaporation rate as a fitting parameter. Scaling relationships obtained from the model for the dependence of the final liquid-front position and total Flow time on the channel dimensions and rate of uniform evaporation are found to be in good agreement with experimental observations.
