DROPLETS GENERATION & MANIPULATION

Microfluidic droplets generation with flow focusing… More info

Introduction

Droplets-based microfluidics consists in manipulating discrete volumes of fluids in immiscible phase, such as water droplets in oil.

Advantages

The generation and manipulation of droplets through microfluidics offer tremendous advantages: better control over small volumes of fluid, enhanced mixing, high throughput experiments.

Applications

Droplets generation has a large scale of applications, such as:

Emulsions and foams, Nanoparticles fabrication, Cell Encapsulation, Drug delivery ….

SUPPORTING MATERIALS

PRINCIPLES

Droplet generation in microfluidic chip

Microfluidic droplets generation systems are used to create monodispersed water or oil droplets in an immiscible phase. In passive droplets production methods, the key principle is to use at least two streams of immiscible fluids and to create a shear force on one of the phases in order to break the stream in discrete droplets.

They are two main motivations for creating microfluidic droplets. The first one is to generate droplets with a very high monodispersity, and microfluidic offers very consistent size of droplets, contrary to conventional batch methods for emulsion productions. Material science applications, such as food or pharmaceutical industries, greatly benefit from these new microfluidic techniques.

The second one is to compartmentalize a given sample. Microfluidic droplets are then a way to manipulate very small and precise volumes of samples, but also to realize high throughput experiments, as each droplet become a distinct microreactor. Moreover, droplets are a way to enhance mixing of chemical and overcome one of the most fundamental issue of single phase microfluidics.

MAIN APPLICATIONS

Microfluidic Droplets in capillary

The applications for microfluidic droplets include:

Single cell analysis
Chemical reactions
Diagnostic applications (lab on chips)
Controlled drug delivery

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FORMATION METHODS

The 2 mains methods:

There are different methods to produce droplets and we present here the two most used methods for digital microfluidics. These methods use two immiscible phases (usually water and oil) and specific chip designs allowing to break one of the streams in discrete droplets.

In these two methods, a very accurate flow control system is necessary to obtain a precise control over the droplets parameters (size and frequency).

For more detailed protocoles, please check our application note.

Droplets generation tips

Surface wettability: This is a crucial parameter to avoid droplets sticking to the chip’s walls. For water-in-oil droplets, the surface must be hydrophobic. For oil-in-water droplets, the surface must be hydrophilic.

Surfactant: The use of surfactant helps prevent droplets coalition.

Flow focusing method

MICROFLUIDICS DROPLET DRIPPING REGIME FLOW FOCUSING

In the flow focusing method, the middle phase is squeezed between two streams of the continuous phase.

T junction method

MICROFLUIDICS-DROPLET-DRIPPING-REGIME-T-JUNCTION-

In this configuration, the two phases are injected (generally with a pressure controller) in two orthogonal channels. The droplet formation occurs at the intersection of the two channels.

REFERENCES

You will find hereafter a short list of microfluidic publications about droplets. If you wish to add a specific publication to this list, please contact us!

  • Baroud, C. N., Gallaire, F., & Dangla, R. (2010). Dynamics of microfluidic droplets. Lab on a Chip, 10(16), 2032-2045.
  • Teh, S. Y., Lin, R., Hung, L. H., & Lee, A. P. (2008). Droplet microfluidics. Lab on a Chip, 8(2), 198-220.
  • I Solvas, X. (2011). Droplet microfluidics: recent developments and future applications. Chemical Communications, 47(7), 1936-1942.
  • Weibel, D. B., & Whitesides, G. M. (2006). Applications of microfluidics in chemical biology. Current opinion in chemical biology, 10(6), 584-591.
  • Song, H., Chen, D. L., & Ismagilov, R. F. (2006). Reactions in droplets in microfluidic channels. Angewandte chemie international edition, 45(44), 7336-7356.
  • Brouzes, E., Medkova, M., Savenelli, N., Marran, D., Twardowski, M., Hutchison, J. B., … & Samuels, M. L. (2009). Droplet microfluidic technology for single-cell high-throughput screening. Proceedings of the National Academy of Sciences, 106(34), 14195-14200.