DOUBLE EMULSIONINTRODUCTION
A double emulsion is defined as a droplet encapsulated within a larger droplet of different
immiscible phases. Making double emulsions is a promising method for many researchers[1] [2] asindustrial fields such as in cosmetics[3] [4] [5], in food applications, food supplement encapsulation[6] [7],in pharmaceutics for drug delivery and others[8] [9].
Though this is a promising method for many applications, conventional technologies to makedouble emulsion, such as batch methods suffer from various limitations[6] [8].
Microfluidics is a promising technology for making double emulsions as it allows one to havebetter control over the sizes and mixtures. This leads to better size distribution, provides
automation possibilities.
Historically, the physical properties of the chip materials have been a limitation for double
emulsions as they have required chemical coatings on the chip or multiple chips. This can leadto additional cost as well as reduce the useful life of the chip.
In this application note we present you a method which allows one to easily produce double
emulsions with any type of solutions, without chemical surface treatments needed , on one
single device (Raydrop).
Different examples of double emulsions (w/o/w and o/w/o droplets) are presented to show theversatility and use of the Raydrop.

This application note was made in collaboration with2

APPLICATION NOTEAPPLICATION NOTE

MATERIAL

METHOD

Reagents:» Dispersed phase: Distilled Water and Fluorescein (Sigma aldrich).
»Continuous phase: 2Different continuous phases have been used during each experiment
depending on the type of emulsion desired:›HFE-7500 (Fluorochem)›Mineral oil (Sigma Aldrich)›dSURF (Fluigent)›Tween 20 (Sigma aldrich)›Span 80 (Sigma aldrich)

Products/Instrument:» Microfluidic flow controller: The Flow EZ is themost advanced flow controller for pressure-based
fluid control. It can be combined with a Flow Unit tocontrol pressure or flow rate. It can be used withouta PC. Two Flow EZ with 2 bar of full scale pressure areused in the setup presented here.
»»»

Flow sensor: The Flow Unit is a flow sensor that allows
real time flow rate measurement. By combining aFlow Unit with the Flow EZ, it is possible to switchfrom pressure control to flow rate control, allowing
for the generation of highly monodispersed droplets
over a long period of time. Two Flow Units M areused here to monitor and control the flow rates ofthe dispersed and continuous phase during the run.

Figure 1: Experimental set-up toproduce double emulsion

Flow EZ™ are used to pressurize the different fluids.
The flow rate of the continuous phase is measured using an L flow-unit from Fluigent while
the Shell phase and the Core phase flow rates are measured using M flow-units. Flow-units arecalibrated by weghing method.

2-Switch: Easy to use 3-port/2-way microfluidic
valve is used to switch between water and alginate
solution. This allows to have better reproducibility bypriming the system and add cleaning step during
the experiment.

To facilitate the start-up of the double emulsion process, 2 switch™ automatic valves are placedon the Shell phase channel and on the Core phase channel.

Droplet generator: The RayDrop droplet andemulsion chip is used to control the generation ofalginate droplets. This is based on the alignment of
two capillaries immersed in a pressurized chamber
containing the continuous phase. The dispersed
phase exits one of the capillaries through a 3D-printed
nozzle, placed in front of the extraction capillary
for collecting the droplets. This non-embedded
implementation of an axisymmetric flow-focusing isreferred to co-flow-focusing. This geometry which isleading the droplet formation removes all wettability
issues that could appear in other chips. It allows one
to generate highly monodispersed emulsions withany kind of fluids including alginate.

Before doing any experiments, fluids are filtered with a 0.2 µm syringe filter.

To avoid any clogging of the double-nozzle, an inline filter A-430 from IDEX with a porosity of
2 µm is installed on each phase channel. Double emulsion production is observed with an IDT
Y3-pro high-speed camera.
A specific setup has been designed to be able to generate double emulsion of fluids presented.
However, depending on the combination of fluids used, the hydraulic resistance on each channel
has to be adapted in order to maintain a larger pressure drop to the Continuous phase than on
the two others and a larger pressure drop on the Shell phase than the Core phase.

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APPLICATION NOTEAPPLICATION NOTERESULTS

Mineral oil light shellIn this second series of experiment, the fluids used are:Water in oil in water (W/O/W)

Even though it is possible toproduce double emulsion without
any surfactant, it’s recommended
to add it to the Continuous andShell phases in order to recover
the double emulsion produced
after formation with good stability.
Surfactant can also be usedwithin the core phase, but it
is rarely needed.

During the experiments, the different flow rates
are changed to produce either core-shell doubleemulsion or double-emulsion with a large shell.
The maximum thickness for the shell will strongly
depends on the fluid configuration. Similarly, theproduction rates attainable will also strongly dependon the fluid configuration.

Shell phasedSURF (HFE +2% Fluigent surfactant)Core phase

Water+0.5% Fluorescein

QcPQs(µl/min) (mBar) (µl/min)

P (mBar)Mineral oil light + 2% Span 80

Core phase

Water+0.5% Fluorescein

PQs

P

P (mBar)

558

1600

9.755175.65931938

4.52 155 µm (max)

116

520

4.0

360

33.9

290

600

2.0

Frequency Production Core(Hz)phase (mL/h)

913

1640

1797

75.6

797

508

4.5

2152 (mw)

83

160

322

12.6

130

217

0.76

Core size
Qc
Qs
P
P
Qcore
P(µm) (µl/min) (mBar) (µl/min) (mBar) (µl/min) (mBar)

108 (min)

77

327

570

816

3

158

306

0.18

4135 (max)

78

85

154

421

1.0

5073

0.06

123Freq. Production Core(Hz)phase (mL/h)

3 122 µm (min)78560

158018.5760

163471063

14 134 µm (max)

98327

1010

6.9415

7.2

220

267

0.43

41

Other example of shell phase
FC40

2Continuous phase

Water+1% Tween 20Shell phase

FC40+2% Krytox 157FSH

Core phase

Water+0.5% Fluorescein

3Ethyl Acetate
45Freq. Production Core(Hz)phase (mL/h)3Large Shell double emulsion
Core size
QcQs
PP
Qcore
P
(µm) (µl/min) (mBar) (µl/min) (mBar) (µl/min) (mBar)P

96 (min)

Droplet size

1 120 µm (min)Droplet size

Qcore(µl/min) (mBar)

1Frequency Production Core(µl/min) (mBar)(Hz)
phase (mL/h)
Qcore

Qc

(µl/min) (mBar) (µl/min)

Large Shell double emulsion

Core-shell double emulsion
Droplet size

Shell phase

Droplet size

In this first series of experiment, the fluids used are:Water+1% Tween 20

Water+1% Tween 20

Core-shell double emulsion

dSURF Shell

Continuous phase

Continuous phase

Continuous phase

Water+1% PVA

Shell phase

Ethyl Acetate

Core phase

Water

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APPLICATION NOTEAPPLICATION NOTE

Oil in water in oil (W/O/W)
In this first series of experiment, the fluids used are:Continuous phase

Mineral oil light + 1% Span 80

Shell phase

Water+2% Tween 20Core phase

Mineral oil light

CONCLUSION
In this application note we have demonstrated how we can produced
in a robust different type of double emulsion with a single device.

Core-shell double emulsion
Droplet size
1115QcPQs(µl/min) (mBar) (µl/min)

72.3

790

P (mBar)

1.3

Precise control of the flow allows also to generate high monodispersity(≈2% size dispersion) double emulsion at different frequency totarget different volume production.

Frequency Production Core(µl/min) (mBar)(Hz)
phase (mL/h)
Qcore

530

P

2100

292

Example with common fluids such as water, mineral oils, fluorocarbon
oils and solvents have been demonstrated here. This method can also
be used for production of double emulsion with specific fluids suchas polymer (PLGA, PLA,…), hydrogel (Alginate, agarose,…) and other.

4.5

Large Shell double emulsion
Droplet size
2122

Core size
QcQs
PP
Qcore
P(µm) (µl/min) (mBar) (µl/min) (mBar) (µl/min) (mBar)

76

43.2

400

2.6301600

Freq. Production Core(Hz)phase (mL/h)
109

As a consequence this method is a promising method for different
market and could be used in order to get rid of limitation of current
technologies such as batch methods and other for different
application such as in pharma, food or cosmetic.

0.18

12

Monodispersity Analysis

After generation, double emulsion have been recovered for size measurements andmonodispersity analysis.
Double emulsions have been produced with different fluids and different core and shell sizes
while always maintaining a high monodispersity with a coefficient variation lower than 2%.
For additional information, contact us by email : contact@fluigent.com or consult our website : www.fluigent.com

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APPLICATION NOTEREFERENCES[1] Manuscript, A. (2016). Lab on a Chip. https://doi.org/10.1039/C6LC00367B[2] Li, W., Zhang, L., Ge, X., Xu, B., Qu, L., Choi, C., & Xu, J. (2018). Chem Soc Rev Microfluidic
fabrication of microparticles for biomedical applications. https://doi.org/10.1039/c7cs00263g[3] Asbahani, A. El, Miladi, K., Badri, W., Sala, M., Addi, E. H. A., Casabianca, H., … Lyon, C. B. (2015).
Essential oils : From extraction to encapsulation. International Journal of Pharmaceutics,483(1–2), 220–243. https://doi.org/10.1016/j.ijpharm.2014.12.069[4] Carvalho, I. T., Estevinho, B. N., & Santos, L. (2016). Application of microencapsulated
essential oils in cosmetic and personal healthcare products – a review, 109–119. https://doi.
org/10.1111/ics.12232[5] Gandini, A., Lacerda, T. M., Carvalho, A. J. F., & Trovatti, E. (2016). Progress of Polymers from
Renewable Resources : Furans , Vegetable Oils , and Polysaccharides. https://doi.org/10.1021/
acs.chemrev.5b00264[6] Balanc, B., & Trifkovic, K. (n.d.). Trends in Encapsulation Technologies for Delivery of Food
Bioactive Compounds. https://doi.org/10.1007/s12393-014-9106-7[7] Katouzian, I., & Jafari, S. M. (2016). SC. Trends in Food Science & Technology. https://doi.
org/10.1016/j.tifs.2016.05.002[8] Iqbal, M., Zafar, N., Fessi, H., & Elaissari, A. (2015). Double emulsion solvent evaporation
techniques used for drug encapsulation. International Journal of Pharmaceutics. https://doi.org/10.1016/j.ijpharm.2015.10.057[9] Haney, M. J., Klyachko, N. L., Zhao, Y., Gupta, R., Plotnikova, G., He, Z., … Batrakova, E. V. (2015).
Eshelman School of Pharmacy , University of. Journal of Controlled Release. https://doi.
org/10.1016/j.jconrel.2015.03.033

CONTACT⽇本代理店: 株式会社ASICON
Local distributor in Japan: ASICON Tokyo Ltd.
asicon-tokyo@asicon-tokyo.com
www.asicon-tokyo.com

8For additional information, contact us by email : contact@fluigent.com or consult our website : www.fluigent.com