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System Integration - A Major Step toward Lab on a Chip.

Sin ML, Gao J, Liao JC, Wong PK - J Biol Eng (2011)

Bottom Line: It is increasingly realized that an effective system integration strategy that is low cost and broadly applicable to various biological engineering situations is required to fully realize the potential of microfluidics.In this article, we review several promising system integration approaches for microfluidics and discuss their advantages, limitations, and applications.Future advancements of these microfluidic strategies will lead toward translational lab-on-a-chip systems for a wide spectrum of biological engineering applications.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Aerospace and Mechanical Engineering, University of Arizona, Tucson, AZ 85721, USA. pak@email.arizona.edu.

ABSTRACT
Microfluidics holds great promise to revolutionize various areas of biological engineering, such as single cell analysis, environmental monitoring, regenerative medicine, and point-of-care diagnostics. Despite the fact that intensive efforts have been devoted into the field in the past decades, microfluidics has not yet been adopted widely. It is increasingly realized that an effective system integration strategy that is low cost and broadly applicable to various biological engineering situations is required to fully realize the potential of microfluidics. In this article, we review several promising system integration approaches for microfluidics and discuss their advantages, limitations, and applications. Future advancements of these microfluidic strategies will lead toward translational lab-on-a-chip systems for a wide spectrum of biological engineering applications.

No MeSH data available.


Multiphase flow droplet microfluidics platform. (A) Droplet formation in microchannels when two immiscible fluid (water and oil) streams merge [220]. (B) Fusion of alternately generated droplets in an expanding channel [99]. (C) Splitting of droplets at the T-junctions [102]. (D) Internal mixing within droplet through a winding microchannel [221]. Arrows show 'flipping' of coloured solution within the droplet.
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Figure 4: Multiphase flow droplet microfluidics platform. (A) Droplet formation in microchannels when two immiscible fluid (water and oil) streams merge [220]. (B) Fusion of alternately generated droplets in an expanding channel [99]. (C) Splitting of droplets at the T-junctions [102]. (D) Internal mixing within droplet through a winding microchannel [221]. Arrows show 'flipping' of coloured solution within the droplet.

Mentions: Multiphase microfluidic systems are typically driven by external pressure sources. Droplets, or bioreacters, in sub-nanoliter volume can be formed spontaneously in the microchannel when two immiscible fluid streams such as water and oil merge [94] (Figure 4a). The droplets can be generated using two channel geometries: T-junction and flow-focusing. The T-junction droplet generator relies on the shear force created at the junction [95] whereas the flow-focusing droplet generator combines sheath flow with a restriction to generate droplets continuously [96]. The size of the droplets can be regulated by the channel geometry, fluid flow rates, and the relative viscosity between the two solutions [97,98]. With the flow-focusing structure, monodispersed pico- to femtoliter sized droplets can be generated at adjustable rates. The formation of more complex double emulsions, such as water-in-oil-in-water (W/O/W) and oil-in-water-in-oil (O/W/O), can be obtained using two consecutive flow-focusing devices [99,100]. Various droplet processes such as fusion, fission, and mixing have been demonstrated by adjusting the flow rate and channel designs [93]. For example, droplet fusion can be initiated by incorporating an expanded portion in the microchannel [101] (Figure 4b) while splitting droplets can utilize shear forces generated by appropriate channel designs, such as T-junctions [102] and branching channels [103] (Figure 4c). For droplets containing multiple reagents, mixing within a droplet can be enhanced geometrically using channels with bends and turns [104] or small protrusions [105], which create chaotic advection for folding and stretching of droplet contents (Figure 4d). Droplet incubation is another essential operation for various biochemical reactions. If the incubation time is long (e.g. over one hour), the droplets can be incubated in on-chip or off-chip reservoirs and reinjected into the device for further analysis. For short incubation time below one hour, a delay-line with a two-depth channel has been reported with minimum back pressure and low dispersion in incubation time [106]. Moreover, bubbles travelling in a microchannel can implement computation and represent a bit for transporting materials and performing logical control operations [107].


System Integration - A Major Step toward Lab on a Chip.

Sin ML, Gao J, Liao JC, Wong PK - J Biol Eng (2011)

Multiphase flow droplet microfluidics platform. (A) Droplet formation in microchannels when two immiscible fluid (water and oil) streams merge [220]. (B) Fusion of alternately generated droplets in an expanding channel [99]. (C) Splitting of droplets at the T-junctions [102]. (D) Internal mixing within droplet through a winding microchannel [221]. Arrows show 'flipping' of coloured solution within the droplet.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3117764&req=5

Figure 4: Multiphase flow droplet microfluidics platform. (A) Droplet formation in microchannels when two immiscible fluid (water and oil) streams merge [220]. (B) Fusion of alternately generated droplets in an expanding channel [99]. (C) Splitting of droplets at the T-junctions [102]. (D) Internal mixing within droplet through a winding microchannel [221]. Arrows show 'flipping' of coloured solution within the droplet.
Mentions: Multiphase microfluidic systems are typically driven by external pressure sources. Droplets, or bioreacters, in sub-nanoliter volume can be formed spontaneously in the microchannel when two immiscible fluid streams such as water and oil merge [94] (Figure 4a). The droplets can be generated using two channel geometries: T-junction and flow-focusing. The T-junction droplet generator relies on the shear force created at the junction [95] whereas the flow-focusing droplet generator combines sheath flow with a restriction to generate droplets continuously [96]. The size of the droplets can be regulated by the channel geometry, fluid flow rates, and the relative viscosity between the two solutions [97,98]. With the flow-focusing structure, monodispersed pico- to femtoliter sized droplets can be generated at adjustable rates. The formation of more complex double emulsions, such as water-in-oil-in-water (W/O/W) and oil-in-water-in-oil (O/W/O), can be obtained using two consecutive flow-focusing devices [99,100]. Various droplet processes such as fusion, fission, and mixing have been demonstrated by adjusting the flow rate and channel designs [93]. For example, droplet fusion can be initiated by incorporating an expanded portion in the microchannel [101] (Figure 4b) while splitting droplets can utilize shear forces generated by appropriate channel designs, such as T-junctions [102] and branching channels [103] (Figure 4c). For droplets containing multiple reagents, mixing within a droplet can be enhanced geometrically using channels with bends and turns [104] or small protrusions [105], which create chaotic advection for folding and stretching of droplet contents (Figure 4d). Droplet incubation is another essential operation for various biochemical reactions. If the incubation time is long (e.g. over one hour), the droplets can be incubated in on-chip or off-chip reservoirs and reinjected into the device for further analysis. For short incubation time below one hour, a delay-line with a two-depth channel has been reported with minimum back pressure and low dispersion in incubation time [106]. Moreover, bubbles travelling in a microchannel can implement computation and represent a bit for transporting materials and performing logical control operations [107].

Bottom Line: It is increasingly realized that an effective system integration strategy that is low cost and broadly applicable to various biological engineering situations is required to fully realize the potential of microfluidics.In this article, we review several promising system integration approaches for microfluidics and discuss their advantages, limitations, and applications.Future advancements of these microfluidic strategies will lead toward translational lab-on-a-chip systems for a wide spectrum of biological engineering applications.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Aerospace and Mechanical Engineering, University of Arizona, Tucson, AZ 85721, USA. pak@email.arizona.edu.

ABSTRACT
Microfluidics holds great promise to revolutionize various areas of biological engineering, such as single cell analysis, environmental monitoring, regenerative medicine, and point-of-care diagnostics. Despite the fact that intensive efforts have been devoted into the field in the past decades, microfluidics has not yet been adopted widely. It is increasingly realized that an effective system integration strategy that is low cost and broadly applicable to various biological engineering situations is required to fully realize the potential of microfluidics. In this article, we review several promising system integration approaches for microfluidics and discuss their advantages, limitations, and applications. Future advancements of these microfluidic strategies will lead toward translational lab-on-a-chip systems for a wide spectrum of biological engineering applications.

No MeSH data available.