Production of solid-stabilised emulsions through rotational membrane emulsification: influence of particle adsorption kinetics

Abstract

There is currently a significant interest in the production of stable emulsions using particulate emulsifiers. A key design and manufacturing challenge in such systems is the production of emulsions with controlled droplet sizes and narrow polydispersity; one candidate production technique is membrane emulsification. In this study we demonstrate that under optimal conditions, highly stable near monodisperse tricaprylin droplets stabilised with 800 nm silica colloids can be achieved using Rotating Membrane Emulsification (RME). We report the influence of various mechanical and chemical parameters on the droplet sizes and size distributions. The optimal conditions for highly stable emulsions with narrow size distributions using the RME approach are described. Investigating the rotational speed and particle concentration in particular highlights the importance of particle adsorption kinetics onto a growing droplet on the detachment of that droplet from the membrane. The data clearly show that if the particles attach and adsorb to the interface before a critical droplet detachment time, stable monodisperse droplets are produced. However, if the adsorption time takes longer than this critical value, the partially stabilized droplets can coalesce and we observe a wider size distribution.

Pickering emulsions: Preparation processes, key parameters governing their properties and potential for pharmaceutical applications

“…Techniques derived from the DME principle using low shear forces acting on the surface of the membrane to detach the droplets are also used, such as the stirred-cell membrane emulsification (SCME) [95,110], the rotational membrane emulsification (RME) [97,111], the vibrational membrane emulsification (VME) [112] and the cross-flow membrane emulsification (XME) [97]. For the SCME (Figure 3d), an additional mechanical agitation is applied in the receptor chamber [95].…”

“…as the shear is low, there is no risk of disruption for sensitive particles or particles aggregates [97]; ii) producing small, size-controlled and uniform emulsions with low polydispersity [97,110,113]; iii) consuming low energy, inducing a low running cost [95]; and iv) producing no heat during the emulsification process, and thus limiting the risk of destabilization for thermosensitive particles and emulsions. [114], c) cross-flow membrane emulsification (XME), adapted from Yuan et al [115], d) rotational membrane emulsification (RME), adapted from Manga et al [111] and e) stirred-cell membrane emulsification (SCME).…”

“…Finally, an agitation/rotation speed increase leads to a droplet size decrease, because it induces an easier detachment of the droplets from the membrane [97,111]. At low rotation speed, the shear is very low.…”

Structured microparticles with tailored properties produced by membrane emulsification

“…Pickering particles are significantly larger than surfactant molecules (100 nm to 20 µm compared to 0.4−5 nm), which leads to slower kinetics of adsorption at the interface and higher energy barriers to adsorption and thus, ME must be performed at low transmembrane flux to allow enough time for stabilisation of growing droplets prior to pinch-off. As long as the particle adsorption time is shorter than the droplet formation time it is possible to produce well controlled droplet sizes (Manga et al, 2012). Yuan et al (2010) prepared O/W Pickering emulsions composed of ethyl acetate solutions stabilised by silica nanoparticles (80 or 800 nm) using a rotating membrane reactor with stainless steel membrane and cross-flow ME with a tubular multi-channel ceramic membrane.…”

Industrial lab-on-a-chip: Design, applications and scale-up for drug discovery and delivery

“…[154] or rotating [155][156][157] or vibrating [158,159] the membrane within otherwise static 17 continuous phase.…”