Droplet production methods

Droplet production is a topical issue for many fields of application, from the food industry, organic chemistry to biological applications.

This review summarizes the main droplet production methods, from the more common batch methods to microfluidics.

It introduces you to the concept of pressure-driven flow controlled microfluidics for droplet generation.

Droplet production methods: batch

The first droplet production method described in the review is the droplet generation batch method.

The most common batch method can be performed as simply as by mixing water and oil in a jar and shaking it thoroughly. The resulting mixture of two immiscible fluids termed “emulsion” will disappear over time due to destabilizing phenomena (coalescence, Ostwald ripening).

The instability can be avoided by several means:

• By adding amphililic molecules or surfactants to one of the two immiscibles phases to reduce the interfacial tension between the two phases.
• By generating monodisperse droplets forming the emulsion to prevent Ostwald ripening.
• By adjusting the rheological properties of the two phases (continuous & disperse) such as the viscosity.

At bigger scale, the process of mixing two immiscibles fluids can be performed with high-shear mixers. High-shear mixing still induces emulsion instability due to the lack of control over the resulting droplet size. Since two decades, microfluidics has slowly taken over the use of high-shear mixers for droplet batch methods to generate highly monodispersed droplets and to fabricate stable emulsions for many fields of application.

Droplet production methods: microfluidics

Droplet-based microfluidics describes the action of generating and manipulating micron sized droplets [1].

Part of droplet production methods, droplet microfluidics allows for:

• Droplet production & handling as a single picoliter volume microreactor.
• High monodisperse droplet generation (CV < 2%).
• Miniaturization of production, handling and analysis of reagents (biological or chemical) [2, 3].

To learn more about droplet-based microfluidics, watch this video!

(better enjoyed with your sound on)

To discover more tips and tricks about droplet-based microfluidics, please check our new droplet userguide!

Want to implement microfluidics instead of droplet batch methods?

To produce droplets with microfluidics, you need:

• To mix two immiscible fluids (eg. water-in-oil or oil-in-water).
• To select the right surfactant to generate stable droplets or emulsions.
• To choose a suitable microfluidic chip (flow-focusing, co-flow or T-junction) to ensure the right size of droplets generated with a laminar flow regime.
• To identify the Flow control system to ensure reproducible experiment & effective control over the droplet size and generation frequency.

To determine the best flow control system for droplet-based microfluidics, watch these two videos!

Based on our best-selling OB1 Flow Controllers, this complete solution contains all the required parts for any researcher’s needs, to start making droplets and emulsions out of the box.

It brings the many benefits of microfluidics, such as excellent monodispersity, reproducibility and scalability to your daily work, in order to achieve great science.

References