Over the past few decades, core-shell microcapsules have been extensively used for the delivery and release of materials in the pharmaceutical, cosmetic, and food industries [1]. The encapsulation of Active Pharmaceutical Compounds in core-shell microcapsule is of great interest for several purposes: taste and odor masking, controlled release of drugs… In pharmaceutics the possibility to encapsulate drugs, nutrients, and living cells that can be protected by a solid biocompatible shell in order to target a specific site is an intense field of research.

However, classical methods of microencapsulation, like coacervation, spray drying, solvent evaporation, etc, require complex process and equipment and make difficult to control the size and load of the microcapsules.

In contrast, microfluidics allows to produce monodisperse double emulsions which lead to monodispersed microcapsules with a high control over both the size and the structure. Microfluidics tools are also used in order to create capsules of varying compositions. With this technology, it is possible to encapsulate aqueous or oily phases. The encapsulation of aqueous phases allows the capsule to contain proteins or active pharmaceutical ingredients (APIs). On the other hand, oily phases containing lipophilic or poorly water-soluble drugs can also be encapsulated. Moreover, capsules can be used for drug delivery or acid-triggered gastric delivery depending on the composition of the shell.

In this Application Note, capsules are formed by consolidating shell phase of the resulting double emulsions by UV-crosslinking of polymers [2] and photoinitiator used as shell phase. Core and continuous phases are aqueous phases non-miscible with the shell. Fine control of the fluid flows leads to defined capsule and shell dimensions. In-situ polymerization is achieved, meaning that the droplets are exposed to UV-light while still being moving forward in the output tubing connected to the Raydrop®. Hard shell microcapsules are thus directly collected in the collection vial. The in-situ process allows to avoid coalescence and deformation of the droplets that can arise in an ex-situ process where the droplets are polymerized after collection.


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