Application note: Multiple emulsions
Traditionally, batch methods are used to produce emulsions in industry. The use of bulk mixing allows to produce huge quantities of emulsions but to the detriment of quality. Indeed, the shear distribution in a bulk mixer is various, leading to numerous particles sizes and a low encapsulation rate in the case of API encapsulation or double emulsion production (core-shell particles). [I] A fortiori, batch method makes the control of multiple emulsions more complex, i.e. the encapsulation of a precise number of droplets of liquid A in a droplet of liquid B.
In general, the use of microfluidics helps to reach low size dispersity and so monodispersed emulsions with a high control over both the size and structure can be obtained. [II] Microfluidic tools are also used to create emulsions of varying compositions. With this technology, it is possible to produce water–in-oil–in-water (W/O/W) emulsions or oil–in-water–in-oil (O/W/O) emulsions. A microfluidic device developed by Secoya Technologies – called the RayDrop® – allows to easily produce such highly controlled emulsions. Examples of applications in double emulsion can be found in the white paper entitled Generation of microcapsules, available on our website https://secoya-tech.com/documents/.
Inspired by the publication of LI, Er Qiang and al. [III], we wanted to demonstrate the possibility to produce multiple emulsions using the RayDrop®. For instance, these multiple emulsions are precursors in the creation of solid microcapsules used for triggered release. [I] Furthermore, these multicompartmental microspheres are interesting to co-encapsulate incompatible solutions (which would react if they were in contact). [IV]
In this Application Note, aqueous droplets (called “core”) in an oily droplet (called “shell”) are obtained using the combination of two RayDrop® devices placed in series. The influence of the fluidic parameters on the number of cores contained in the oily shell is underlined in this application note.
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