Production of Nanoemulsions Using Anodic Alumina Membranes in a Stirred-Cell Setup

Oil-in-water nanoemulsions (NEs) were produced in a dead-end stirred cell setup for the first time using bespoke anodic alumina membranes (AAMs). The regular pore structure and narrow pore size distribution of AAMs enabled the formation of NEs with narrow size distributions. Rotational speed and membrane pore size were the key parameters in controlling the droplet size, with droplets as small as 144 ± 18 nm obtained using a membrane with a pore size of 58 ± 6 nm. Low values of the droplet diameter to pore diameter ratio, ranging from 1.8 to 3.5, were obtained, compared to typical literature values of ∼10. Literature droplet size prediction models for microemulsions overestimate results by up to ∼600%, whereas a model developed by the authors for NEs is much closer to experimental values. These results show that stable and controlled NEs can be produced for a variety of applications, ranging from consumer products to materials manufacturing, potentially at large scale.