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Microfluidic device for robust generation of two-component liquid-in-air slugs with individually controlled composition.

Liu K, Chen YC, Tseng HR, Shen CK, van Dam RM - Microfluid Nanofluidics (2010)

Bottom Line: The use of microvalves in this approach enables robust operation with different liquids, and also enables one to work with extremely small samples, even down to a few slug volumes.The latter is important for applications involving precious reagents such as optimizing the reaction conditions for radiolabeling biological molecules as tracers for positron emission tomography.ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10404-010-0617-0) contains supplementary material, which is available to authorized users.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular & Medical Pharmacology, Crump Institute for Molecular Imaging, California NanoSystems Institute, David Geffen School of Medicine, University of California, Los Angeles, 570 Westwood Plaza, Los Angeles, CA 90095 USA.

ABSTRACT
Using liquid slugs as microreactors and microvessels enable precise control over the conditions of their contents on short-time scales for a wide variety of applications. Particularly for screening applications, there is a need for control of slug parameters such as size and composition. We describe a new microfluidic approach for creating slugs in air, each comprising a size and composition that can be selected individually for each slug. Two-component slugs are formed by first metering the desired volume of each reagent, merging the two volumes into an end-to-end slug, and propelling the slug to induce mixing. Volume control is achieved by a novel mechanism: two closed chambers on the chip are initially filled with air, and a valve in each is briefly opened to admit one of the reagents. The pressure of each reagent can be individually selected and determines the amount of air compression, and thus the amount of liquid that is admitted into each chamber. We describe the theory of operation, characterize the slug generation chip, and demonstrate the creation of slugs of different compositions. The use of microvalves in this approach enables robust operation with different liquids, and also enables one to work with extremely small samples, even down to a few slug volumes. The latter is important for applications involving precious reagents such as optimizing the reaction conditions for radiolabeling biological molecules as tracers for positron emission tomography. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10404-010-0617-0) contains supplementary material, which is available to authorized users.

No MeSH data available.


a Fraction filled of one slug generator chamber with water as a function of filling pressure, Pfill, at fixed tfill = 100 ms and fixed Pinitial = 60 kPag (Pcarrier) or 0 kPag (vented). Solid lines show the theoretical ideal gas model for the cases of Pinitial = 60 and 10 kPag. The latter resulted in closer agreement than with Pinitial = 0 kPag, suggesting that in the experiment the pressure was not completely vented prior to filling (only 5-s venting time was used). Dotted lines represent the model with modifications for PDMS expansion. b Fraction filled of one slug generator chamber with water as a function of initial pressure, Pinitial, at fixed Pfill of 70, 140 and 210 kPag, and fixed tfill = 100 ms. Solid lines represent the ideal gas model for the selected fixed filling pressures, and the dotted lines represent the theory with modifications for PDMS expansion. c Conceptual model of PDMS channel expansion and the effect on filling fraction. (i) Initially chamber is filled with air. (ii) The chamber is filled to a fraction, f, but the channel cross-section is increased (due to elastic deformation by internal pressure Pfill) so the absolute amount of liquid in the chamber is larger would be expected if there is no expansion. (iii) Air remaining in the chamber after filling escapes via permeation reducing the pressure. (iv) The channel relaxes to its original cross-section, distributing the liquid to fill a longer portion of the channel. It is the relaxed length that is measured
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Fig4: a Fraction filled of one slug generator chamber with water as a function of filling pressure, Pfill, at fixed tfill = 100 ms and fixed Pinitial = 60 kPag (Pcarrier) or 0 kPag (vented). Solid lines show the theoretical ideal gas model for the cases of Pinitial = 60 and 10 kPag. The latter resulted in closer agreement than with Pinitial = 0 kPag, suggesting that in the experiment the pressure was not completely vented prior to filling (only 5-s venting time was used). Dotted lines represent the model with modifications for PDMS expansion. b Fraction filled of one slug generator chamber with water as a function of initial pressure, Pinitial, at fixed Pfill of 70, 140 and 210 kPag, and fixed tfill = 100 ms. Solid lines represent the ideal gas model for the selected fixed filling pressures, and the dotted lines represent the theory with modifications for PDMS expansion. c Conceptual model of PDMS channel expansion and the effect on filling fraction. (i) Initially chamber is filled with air. (ii) The chamber is filled to a fraction, f, but the channel cross-section is increased (due to elastic deformation by internal pressure Pfill) so the absolute amount of liquid in the chamber is larger would be expected if there is no expansion. (iii) Air remaining in the chamber after filling escapes via permeation reducing the pressure. (iv) The channel relaxes to its original cross-section, distributing the liquid to fill a longer portion of the channel. It is the relaxed length that is measured

Mentions: Equation 2 predicts that with a fixed filling time selected just after the end of the compression phase, the filling fraction depends on both the filling pressure Pfill and the initial pressure, Pinitial. Experimentally, the expected dependence on both the pressures is seen (see Fig. 4a, b), and comparison with the ideal gas model (solid line) after conversion of gauge to absolute pressures of Eq. 2 shows good agreement at low Pfill. However, there is increasing discrepancy between experimental data and the model at higher filling pressures, presumably due to the expansion of the PDMS channel under pressure. Modeling of this effect is discussed in the next section.Fig. 4


Microfluidic device for robust generation of two-component liquid-in-air slugs with individually controlled composition.

Liu K, Chen YC, Tseng HR, Shen CK, van Dam RM - Microfluid Nanofluidics (2010)

a Fraction filled of one slug generator chamber with water as a function of filling pressure, Pfill, at fixed tfill = 100 ms and fixed Pinitial = 60 kPag (Pcarrier) or 0 kPag (vented). Solid lines show the theoretical ideal gas model for the cases of Pinitial = 60 and 10 kPag. The latter resulted in closer agreement than with Pinitial = 0 kPag, suggesting that in the experiment the pressure was not completely vented prior to filling (only 5-s venting time was used). Dotted lines represent the model with modifications for PDMS expansion. b Fraction filled of one slug generator chamber with water as a function of initial pressure, Pinitial, at fixed Pfill of 70, 140 and 210 kPag, and fixed tfill = 100 ms. Solid lines represent the ideal gas model for the selected fixed filling pressures, and the dotted lines represent the theory with modifications for PDMS expansion. c Conceptual model of PDMS channel expansion and the effect on filling fraction. (i) Initially chamber is filled with air. (ii) The chamber is filled to a fraction, f, but the channel cross-section is increased (due to elastic deformation by internal pressure Pfill) so the absolute amount of liquid in the chamber is larger would be expected if there is no expansion. (iii) Air remaining in the chamber after filling escapes via permeation reducing the pressure. (iv) The channel relaxes to its original cross-section, distributing the liquid to fill a longer portion of the channel. It is the relaxed length that is measured
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Related In: Results  -  Collection

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Fig4: a Fraction filled of one slug generator chamber with water as a function of filling pressure, Pfill, at fixed tfill = 100 ms and fixed Pinitial = 60 kPag (Pcarrier) or 0 kPag (vented). Solid lines show the theoretical ideal gas model for the cases of Pinitial = 60 and 10 kPag. The latter resulted in closer agreement than with Pinitial = 0 kPag, suggesting that in the experiment the pressure was not completely vented prior to filling (only 5-s venting time was used). Dotted lines represent the model with modifications for PDMS expansion. b Fraction filled of one slug generator chamber with water as a function of initial pressure, Pinitial, at fixed Pfill of 70, 140 and 210 kPag, and fixed tfill = 100 ms. Solid lines represent the ideal gas model for the selected fixed filling pressures, and the dotted lines represent the theory with modifications for PDMS expansion. c Conceptual model of PDMS channel expansion and the effect on filling fraction. (i) Initially chamber is filled with air. (ii) The chamber is filled to a fraction, f, but the channel cross-section is increased (due to elastic deformation by internal pressure Pfill) so the absolute amount of liquid in the chamber is larger would be expected if there is no expansion. (iii) Air remaining in the chamber after filling escapes via permeation reducing the pressure. (iv) The channel relaxes to its original cross-section, distributing the liquid to fill a longer portion of the channel. It is the relaxed length that is measured
Mentions: Equation 2 predicts that with a fixed filling time selected just after the end of the compression phase, the filling fraction depends on both the filling pressure Pfill and the initial pressure, Pinitial. Experimentally, the expected dependence on both the pressures is seen (see Fig. 4a, b), and comparison with the ideal gas model (solid line) after conversion of gauge to absolute pressures of Eq. 2 shows good agreement at low Pfill. However, there is increasing discrepancy between experimental data and the model at higher filling pressures, presumably due to the expansion of the PDMS channel under pressure. Modeling of this effect is discussed in the next section.Fig. 4

Bottom Line: The use of microvalves in this approach enables robust operation with different liquids, and also enables one to work with extremely small samples, even down to a few slug volumes.The latter is important for applications involving precious reagents such as optimizing the reaction conditions for radiolabeling biological molecules as tracers for positron emission tomography.ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10404-010-0617-0) contains supplementary material, which is available to authorized users.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular & Medical Pharmacology, Crump Institute for Molecular Imaging, California NanoSystems Institute, David Geffen School of Medicine, University of California, Los Angeles, 570 Westwood Plaza, Los Angeles, CA 90095 USA.

ABSTRACT
Using liquid slugs as microreactors and microvessels enable precise control over the conditions of their contents on short-time scales for a wide variety of applications. Particularly for screening applications, there is a need for control of slug parameters such as size and composition. We describe a new microfluidic approach for creating slugs in air, each comprising a size and composition that can be selected individually for each slug. Two-component slugs are formed by first metering the desired volume of each reagent, merging the two volumes into an end-to-end slug, and propelling the slug to induce mixing. Volume control is achieved by a novel mechanism: two closed chambers on the chip are initially filled with air, and a valve in each is briefly opened to admit one of the reagents. The pressure of each reagent can be individually selected and determines the amount of air compression, and thus the amount of liquid that is admitted into each chamber. We describe the theory of operation, characterize the slug generation chip, and demonstrate the creation of slugs of different compositions. The use of microvalves in this approach enables robust operation with different liquids, and also enables one to work with extremely small samples, even down to a few slug volumes. The latter is important for applications involving precious reagents such as optimizing the reaction conditions for radiolabeling biological molecules as tracers for positron emission tomography. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10404-010-0617-0) contains supplementary material, which is available to authorized users.

No MeSH data available.