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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 deionized water as a function of filling time (tfill) at Pfill = 140 kPag, illustrating the time evolution of the filling process. Pcarrier was 60 kPag and Pinitial was 0 kPag (i.e., using venting) for all measurements. b Detail of filling for the first 1 s. c Conceptual model of two-phase filling process. (i) Initially the chamber is filled with air. (ii) During the first filling phase, the air is rapidly compressed, allowing part of the chamber to be filled with liquid. (iii) In the second phase, the compressed air slowly leaks through the PDMS chip, permitting additional liquid to enter the chamber. (iv) Finally, the inlet valve is closed, trapping the liquid in the chamber
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Fig3: a Fraction filled of one slug generator chamber with deionized water as a function of filling time (tfill) at Pfill = 140 kPag, illustrating the time evolution of the filling process. Pcarrier was 60 kPag and Pinitial was 0 kPag (i.e., using venting) for all measurements. b Detail of filling for the first 1 s. c Conceptual model of two-phase filling process. (i) Initially the chamber is filled with air. (ii) During the first filling phase, the air is rapidly compressed, allowing part of the chamber to be filled with liquid. (iii) In the second phase, the compressed air slowly leaks through the PDMS chip, permitting additional liquid to enter the chamber. (iv) Finally, the inlet valve is closed, trapping the liquid in the chamber

Mentions: First, the temporal aspects of the filling process were studied. Using a single chamber, filling fraction of deionized water was measured as a function of filling time, tfill (Fig. 3). Filling was observed to proceed in two distinct phases with very different time scales. Initially, within tens of milliseconds, the chamber fills to a certain fraction (shown later to depend on filling pressure, Pfill). The second phase is much slower (tens of seconds) and appears approximately linear. The combination of very high and very low slopes makes it difficult to use tfill as a means to control the fraction filled over a wide range. However, the insensitivity to time (e.g., 4.4% per second for the first 1 s in Fig. 3) does have an advantage: if tfill is chosen within the second phase, filling fraction will not be sensitive to small inaccuracies in filling time (e.g., tens to hundreds of milliseconds) that may arise due to factors such as electronics delays and finite valve response time.Fig. 3


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 deionized water as a function of filling time (tfill) at Pfill = 140 kPag, illustrating the time evolution of the filling process. Pcarrier was 60 kPag and Pinitial was 0 kPag (i.e., using venting) for all measurements. b Detail of filling for the first 1 s. c Conceptual model of two-phase filling process. (i) Initially the chamber is filled with air. (ii) During the first filling phase, the air is rapidly compressed, allowing part of the chamber to be filled with liquid. (iii) In the second phase, the compressed air slowly leaks through the PDMS chip, permitting additional liquid to enter the chamber. (iv) Finally, the inlet valve is closed, trapping the liquid in the chamber
© Copyright Policy
Related In: Results  -  Collection

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Fig3: a Fraction filled of one slug generator chamber with deionized water as a function of filling time (tfill) at Pfill = 140 kPag, illustrating the time evolution of the filling process. Pcarrier was 60 kPag and Pinitial was 0 kPag (i.e., using venting) for all measurements. b Detail of filling for the first 1 s. c Conceptual model of two-phase filling process. (i) Initially the chamber is filled with air. (ii) During the first filling phase, the air is rapidly compressed, allowing part of the chamber to be filled with liquid. (iii) In the second phase, the compressed air slowly leaks through the PDMS chip, permitting additional liquid to enter the chamber. (iv) Finally, the inlet valve is closed, trapping the liquid in the chamber
Mentions: First, the temporal aspects of the filling process were studied. Using a single chamber, filling fraction of deionized water was measured as a function of filling time, tfill (Fig. 3). Filling was observed to proceed in two distinct phases with very different time scales. Initially, within tens of milliseconds, the chamber fills to a certain fraction (shown later to depend on filling pressure, Pfill). The second phase is much slower (tens of seconds) and appears approximately linear. The combination of very high and very low slopes makes it difficult to use tfill as a means to control the fraction filled over a wide range. However, the insensitivity to time (e.g., 4.4% per second for the first 1 s in Fig. 3) does have an advantage: if tfill is chosen within the second phase, filling fraction will not be sensitive to small inaccuracies in filling time (e.g., tens to hundreds of milliseconds) that may arise due to factors such as electronics delays and finite valve response time.Fig. 3

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.