Manufacture of large uniform droplets using rotating membrane emulsification

Abstract

A new rotating membrane emulsification system using a stainless steel membrane with 100 µm laser drilled pores was used to produce oil/water emulsions consisting of 2 wt. % Tween 20 as emulsifier, paraffin wax as dispersed oil phase and 0.01-0.25 wt. % Carbomer (Carbopol ETD 2050) as stabilizer. The membrane tube, 1 cm in diameter, was rotated inside a stationary glass cylinder, diameter of 3 cm, at a constant speed in the range 50-1500 rpm. The oil phase was introduced inside the membrane tube and permeated through the porous wall moving radially into the continuous phase in the form of individual droplets. Increasing the membrane rotational speed increased the wall shear stress which resulted in a smaller average droplet diameter being produced. For a constant rotational speed, the average droplet diameter increased as the stabilizer content in the continuous phase was lowered. The optimal conditions for producing uniform emulsion droplets were a Carbomer content of 0.1-0.25 wt. % and a membrane rotational speed of 350 rpm, under which the average droplet diameter was 105-107 µm and very narrow coefficients of variation of 4.8-4.9 %. A model describing the operation is described and it is concluded that the methodology holds potential as a manufacturing protocol for both coarse and fine droplets and capsules.

Production of molecularly imprinted polymer particles with amide-decorated cavities for CO 2 capture using membrane emulsification/suspension polymerisation

“…Membrane emulsification is a "bottom-up" approach based 58 on injection of one liquid through a microporous membrane into another immiscible liquid 59 phase, leading to generation of uniform droplets [29]. Continuous membrane emulsification 60 systems enable large-scale production and can involve oscillatory (pulsed) flow of the 61 continuous phase [29,30] or nonstationary membrane, such as rotating [31] The MIP particles were synthesised through the following five steps:…”

Effect of dispersed phase viscosity on maximum droplet generation frequency in microchannel emulsification using asymmetric straight-through channels

“…Various membrane configurations have been investigated for direct ME including cross-flow systems (Vladisavljević and Schubert, 2003a), rotating stainless steel tube with laser drilled pores (Vladisavljević and Williams, 2006), vibrating microsieve membrane (Holdich et al 2010) and stirred cell with flat-disc membrane (Egidi et al 2008). ME enables production of emulsions over a wide range of mean droplet sizes from about 0.3 µm to several hundred µm with a width of the particle size distribution typically in the range of 0.3−0.6 as measured by relative span factor (Table A1) or above 10% in terms of coefficient of variation (CV).…”

Structured microparticles with tailored properties produced by membrane emulsification

“…It is especially important in PME, where whole emulsion, rather than a pure dispersed phase, is pressed through the membrane. Typical microsieves used in ME are nickel microengineered membranes manufactured using UV-LIGA process (Nazir et al, 2011;Schadler and Windhab, 2006;Egidi et al, 2008), silicon nitride Aquamarijn microsieves fabricated by reactive ion etching (RIE) (van Rijn et al, 1997), stainless steel membranes fabricated by pulsed laser drilling (Dowding et al, 2001;Vladisavljević and Williams, 2006;Geerken et al, 2008) or end-milling , and microchannel arrays fabricated in single crystal silicon by Deep Reactive Ion Etching (DRIE) (Kobayashi et al, 2003) or in PMMA by X-ray lithography and wet etching (Kobayashi et al, 2008b). The fabrication of microengineered membranes for ME is described by Vladisavljević et al (2012).…”

“…The surface shear can be decoupled from the cross flow by rotating or vibrating the membrane within a static continuous phase (Holdich et al, 2010;Zeng et al, 2013;Gomaa et al, 2014;Vladisavljević and Williams, 2006) or introducing forward and backward flow pulsations in cross flow . The advantages of pulsed cross flow over rotating or vibrating membrane are: (i) liquid pulsations require less energy than membrane oscillations or rotations because liquids are less dense than solids and have a lower inertia; (ii) the energy consumption to maintain pulsed flow is independent on membrane area, whereas energy input to maintain membrane vibrations or rotations is in proportion with membrane dimensions, and (iii) pulsed cross flow can be extended to a baffled reactor, connected in series to the membrane module, to achieve simultaneous drop generation and reaction in the produced emulsion .…”