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Microfluidic fabrication of water-in-water (w/w) jets and emulsions
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10.1063/1.3670365
/content/aip/journal/bmf/6/1/10.1063/1.3670365
http://aip.metastore.ingenta.com/content/aip/journal/bmf/6/1/10.1063/1.3670365
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Figures

Image of FIG. 1.
FIG. 1.

(a) Schematic of a capillary microfluidic device used in this study; (b) optical microscope image showing a jet of 17 wt. % PEG solution in a continuous phase of 16 wt. % dextran solution in the microfluidic device. Flow rates of the PEG solution and the dextran solution are 40 μl/h and 5000 μl/h, respectively; (c) optical microscope image of monodisperse droplets of 17 wt. % PEG solution in 16 wt. % dextran solution with an agitation of the tubing of the dispersed phase at 6.7 Hz. Flow rates of the two phases are the same as those for (b).

Image of FIG. 2.
FIG. 2.

Optical microscope images showing generation of jets and droplets at different frequency of shaking. The dispersed and continuous phases are 17 wt. % PEG solution and 16 wt. % dextran solution, respectively. Flow rates of the PEG solution and the dextran solution are 40 μl/h and 5000 μl/h, respectively. Applied shaking frequencies are (a) 0 Hz, (b) 2.3 Hz, (c) 2.8 Hz, (d) 3.6 Hz, (e) 4.4 Hz, (f) 6.2 Hz, (g) 6.7 Hz, (h) 7.5 Hz, (i) 9.6 Hz, (j) 10.9 Hz, (k) 15 Hz, and (l) 21 Hz.

Image of FIG. 3.
FIG. 3.

(a) A plot of the observed oscillation frequency in a jet as a function of the applied shaking frequency. The observed oscillation frequency is measured by dividing the number of pulses observed inside the device by the elapsed time between fast camera frames. The applied shaking frequency is indicated by the orbital shaker. (b) Optical microscope image of monodisperse water-in-water (w/w) emulsion droplets of 17 wt. % PEG solution in 16 wt. % dextran solution. Inset: optical microscope image of photo-crosslinked PEG-DA particles generated using an ATPS.

Image of FIG. 4.
FIG. 4.

Optical microscope images of droplets of water with 17 wt. % PEG solution and 1 wt. % allura red in a continuous phase of 16 wt. % dextran solution observed at (a) 0 cm, (b) 1 cm, (c) 2 cm, (d) 3 cm, (e) 6 cm, and (f) 7 cm from the tip of the injection tip. The reddening of the continuous phase suggests that allura red in the droplets gradually diffuses into the continuous phase. Scale bar is 200 μm. (g) Profile of grayscale value across a droplet imaged at 0 cm, 1 cm, 2 cm, 6 cm, and 7 cm from the nozzle. The grayscale value is obtained by converting the color images into grayscale images and subsequently measuring the grayscale value, which indicates the color intensity in the original color images. A smaller grayscale value indicates a higher intensity in the original color image. The dashlines in (a), (b), (c), (d), and (f) indicate the line across which the intensity profiles are obtained in the corresponding images. (h) Plot of the difference in the grayscale value between the inside and the outside of a droplet imaged at different distance from the nozzle.

Image of FIG. 5.
FIG. 5.

Interfacial precipitation for enhancing encapsulation efficiency of allura red. Optical microscope images of (a)-(c) jets and (d) droplets of water with 17 wt. % PEG and 1 wt. % calcium chloride in a continuous phase of water with 16 wt. % dextran and 1 wt. % sodium carbonate. Images (a) and (c) are taken at 0.5 cm from the tip of the injection capillary while images (b) and (d) show the same jets as in (a) and (c), respectively, at 2 cm from the tip of the injection capillary. Shaking is only applied to the jet shown in (c) and (d). The calcium ions and the carbonate ions in the dispersed and continuous phases, respectively, react to form a precipitate of calcium carbonate. In (d), the satellite drops form between two larger parent drops since the addition of components for interfacial precipitation modifies the rheological properties of the fluids. Scale bar is 1 mm.

Image of FIG. 6.
FIG. 6.

Interfacial precipitation for enhancing the encapsulation efficiency of allura red viewed as an optical microscope image of a system of 16 wt. % dextran in the continuous phase and 17 wt. % PEG 8000 in the dispersed phase (a) with no encapsulation and (b) with encapsulation using 2 wt. % CaCl2 in the dispersed phase and 2 wt. % Na2CO3 in the continuous phase (flow rates: 5000 μl/h for continuous phase and 100 μl/h for dispersed phase). (c) Profile of normalized grayscale value across a droplet with and without interfacial precipitation imaged at 2 cm from the nozzle. The normalized grayscale value is obtained by converting the color images into grayscale images and subsequently measuring the grayscale value, which indicates the color intensity in the original color images. The resultant values are normalized by the average grayscale value obtained in the continuous phase. A smaller grayscale value indicates a higher intensity in the original color image. The higher difference in the normalized grayscale value between the droplet phase and the continuous phase for the system with interfacial precipitation indicates an enhanced encapsulation efficiency.

Image of FIG. 7.
FIG. 7.

Gelation for enhancing the encapsulation efficiency of allura red. (a) Optical microscope image of a jet of water with 17 wt. % PEG, 1 wt. % allura red and 2 wt. % calcium chloride in a continuous phase of water with 16 wt. % dextran and 1 wt. % alginic acid. Scale bar is 800 μm; (b) and (c) Digital photographs of calcium alginate gel fibers encapsulating allura red prepared using two water-based phases in a capillary microfluidic device. Scale bars are 5 mm and 15 mm in (b) and (c), respectively.

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/content/aip/journal/bmf/6/1/10.1063/1.3670365
2012-03-15
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Microfluidic fabrication of water-in-water (w/w) jets and emulsions
http://aip.metastore.ingenta.com/content/aip/journal/bmf/6/1/10.1063/1.3670365
10.1063/1.3670365
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