Recent developments in manufacturing emulsions and particulate products from double emulsion templates using membrane and microfluidic devices

Membrane and microfluidic devices are relatively new tools for the highly controlled production of multiple emulsions. This review focuses on the recent developments in this area, ranging from the production of multiple emulsions of different types and morphologies (e.g. multiple core-shell structures, outer drops with controlled number of internal droplets, etc) to highly sophisticated functional products such as polymerosomes, asymmetric lipid vesicles, and core-shell particles. Other emerging technologies that extend the capabilities into different membrane materials and operation methods (such as rotating stainless steel membrane with laser drilled pores) and manufacturing approaches (extrusion of pure to-be-dispersed phase or coarsely emulsified feeds) are introduced. The use of microfluidic devices such as T-junctions, flow focusing devices and silicon microchannel array devices is also reviewed. The results of experimental work carried out by cited researchers in the field together with those of the current authors are presented in a tabular form in a rigorous and systematic manner. These demonstrate a wide range of products that can be manufactured from multiple emulsions using different membrane and microfluidic approaches. Opportunities for creation of new and novel entities are highlighted for low throughput applications (medical diagnostics, healthcare) and for large scale productions (consumer and personal products).