Review paper Innovations in high throughput manufacturing of uniform emulsions and capsules Qingchun Yuan, Richard A. Williams * , Nita Aryanti Institute of Particle Science and Engineering, School of Process, Environmental and Materials Engineering, University of Leeds, Leeds LS 2 9JT, United Kingdom article info Keywords: Membrane emulsification Uniform emulsion Microcapsule Encapsulation abstract Membrane emulsification has been widely used in the manufacture of uniform soft and hard spherical particles. It is used to create uniform emulsion droplets whose sizes can be closely controlled. A disperse liquid phase is pressurised to permeate into the pores of a membrane, forming droplets in a drop-by-drop manner in a continuous phase on the other side of the membrane. The droplets formed are detached by applying well controlled detachment forces, which are result from the cross-flow of the continuous phase over the membrane surface, or the rotation of the membrane in the continuous phase. These two tech- nologies are called cross-flow and rotating membrane emulsification, respectively. This paper presents examples of uniform complex spheres, sized from sub-micrometers to a few hundred micrometers, pre- pared using a pilot scale cross-flow membrane emulsification rig and a bentchtop rotating reactor. Emul- sion stabilisation strategies vary from using small molecular surfactants, nanoparticles to surfactant free interfacial polymerisation. The examples demonstrate the advantages and versatility in formulation and manufacture of precisely size- and structure-controlled products using membranes. Ó 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved. Contents 1. Introduction ......................................................................................................... 599 1.1. Membrane emulsification ......................................................................................... 600 1.2. Droplet formation and size control ................................................................................. 601 1.3. Productivity .................................................................................................... 601 2. Experimental ........................................................................................................ 602 2.1. Materials ...................................................................................................... 602 2.2. Rotor–stator homogenisation ...................................................................................... 602 2.3. Cross-flow membrane emulsification................................................................................ 602 2.4. Rotating membrane emulsification ................................................................................. 603 2.5. Particle analysis ................................................................................................. 603 3. Results and discussions ................................................................................................ 604 3.1. Size control of membrane emulsification ............................................................................ 604 3.2. Encapsulation .................................................................................................. 605 3.3. Particle emulsifiers in membrane emulsification ...................................................................... 605 4. Summary remarks .................................................................................................... 607 References .......................................................................................................... 607 1. Introduction Uniform droplets and capsules with closely defined sizes have become increasingly important in product formulations such as food, pharmaceutical, household and personal care sectors [1,2]. Emulsion droplets – as perfect spherical templates – can be used to manufacture various structures soft and hard to meet different application requirements. Conventionally, highly intensive turbu- lence is generated through high speed stirring, rotor–stator homogenisation, high pressure homogenisation or high frequency ultrasonication to break the disperse liquid phase and form drop- lets in an immiscible continuous phase. In these conventional methods, the disperse/continuous phases and emulsifiers are 0921-8831/$ - see front matter Ó 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved. doi:10.1016/j.apt.2010.08.001 * Corresponding author. Tel.: +44 113 3432801. E-mail address: r.a.williams@leeds.ac.uk (R.A. Williams). Advanced Powder Technology 21 (2010) 599–608 Contents lists available at ScienceDirect Advanced Powder Technology journal homepage: www.elsevier.com/locate/apt