Ultrasound control of oil-in-oil Pickering emulsions preparation

Abstract

Particle-stabilised emulsions are of interest to many scientists in both academia and industry as they hold promise for numerous applications. There is a lot of research effort put into developing new methods for their fabrication. Often, different experimental techniques are used for monitoring the process of the emulsion formation. However, the control of the emulsion fabrication and its real-time characterisation is generally challenging. In this work, we propose a convenient method to control fabrication of Pickering emulsions using ultrasound. The benefit of acoustical measurements compared to other techniques is their ability to test the medium in a non-destructive way, without requiring special sample preparation (e.g. dilution like in the case of DLS or NMR) nor a usage of thin sample cells (e.g. in the case of optical microscopy). Here, ultrasonic measurements are able to follow droplets growth during the emulsion development using the limited coalescence approach. We found that ultrasonic attenuation increased with the droplet size within the time frame of droplet stabilisation. Following these changes in ultrasonic attenuation enabled the study of macroscopic behaviour—for example, estimation of a time when droplets achieve their final size and become fully covered by solid particles. These results are compared with the results obtained from the optical measurements. We also make an attempt to theoretically describe ultrasound propagation in particle-stabilised emulsions by comparing our experimental results with the scattering theory ECAH for emulsions.

The Effect of Particle Shell on Cooling Rates in Oil-in-Oil Magnetic Pickering Emulsions

“…The acoustic intensity was estimated as 17 W/cm 2 . As shown in our previous articles [15,23], for oil-in-oil emulsions ultrasonic homogenization resulted in the formation of small droplets barely coated by particles that we consistently called the pre-emulsion. An electric field was utilized to stabilize these droplets via consecutive events of coalescence.…”

Biocompatible Hydrogel-Based Liquid Marbles with Magnetosomes

“…Rather, they were involved in a kind of ‘wrestling’ (trying to push each other), or they ‘buried’ themselves in a bed of particles. This tendency of LMs to either coalesce or merely remain in contact without merging appears to be primarily influenced by the degree of coverage of both droplets with particles at the moment of contact or the presence of large pores in the coating, as we showed for Pickering emulsion droplets coalesced under electric fields [ 60 , 61 ]. However, in the case of LMs, a more detailed examination of the merging process uncovered additional factors influencing their behavior.…”

Pickering Emulsions as Templates for Architecting Composite Structures

“…29 Recently, Pickering surfactants have emerged for the stabilization of o/o emulsions, again imparting steric stabilization to the interface, and not solely relying on decreasing the interfacial tension. 26,30 For example, fumed silica particles, with hydrocarbon groups or fluorocarbon chains, fluoro-silicone particles, 31 plate-like fluorinated calcium lauryl taurate particles, 32 Shigaite-like clay, 33 polystyrene particles, 34 silica particles, 35 diblock copolymer particles, 36,37 alkylated cellulose, 38 and magnetic particles have been reported to stabilize these nonaqueous interfaces. 39 The Pentzer lab developed alkylated graphene oxide (GO) nanosheets for the stabilization of o/o emulsions (Figure 2).…”

“…Molecular brush surfactants have also been reported to stabilize o/o emulsions, even at high internal phase through interfacial jamming of the polymeric brushes . Recently, Pickering surfactants have emerged for the stabilization of o/o emulsions, again imparting steric stabilization to the interface, and not solely relying on decreasing the interfacial tension. , For example, fumed silica particles, with hydrocarbon groups or fluorocarbon chains, fluoro-silicone particles, plate-like fluorinated calcium lauryl taurate particles, Shigaite-like clay, polystyrene particles, silica particles, diblock copolymer particles, , alkylated cellulose, and magnetic particles have been reported to stabilize these nonaqueous interfaces …”