(Droplet generation)

Colloidal clay in water suspensions are known to exhibit a multitude of bulk phases depending on initial colloidal concentration and ionic strength, and examples of this include repulsive Wigner colloidal glasses at low ionic strength and attractive gels at higher ionic strength due to screened electrostatic forces by the electrolyte. From confocal Raman microscopy combined with elasticity measurements, we inferred that clay trapped at quasi two-dimensional interfaces between oil and water also exhibit confined glass-like or gel-like states. The results can be important for the preparation of particles stabilized colloidal emulsions or colloidal capsules, and a better understanding of this phenomenon may lead to new emulsion or encapsulation technologies. Read more

Moreover, we prepared Pickering drops via electric field-driven self-assembly. We used direct current (DC) electric fields to induce mechanical stress on these drops, as a possible alternative to the use of, for example, fluid flow fields. Drop deformation was monitored as a function of the applied electric field strength. The deformation of pure silicone oil drops was enhanced when covered by insulating polyethylene (PE) particles, whereas drops covered by conductive clay particles could also change shape from oblate to prolate. We attributed these results to changes in the electric conductivity of the drop interface after adding particles, and have developed a fluid shell description to estimate the conductivity of Pickering particle layers that were assumed to be non-jammed and fluid-like. Retraction experiments in the absence of electric fields were also performed. Particle-covered drops retracted slower than particle-free drops, caused by increased viscous dissipation due to the presence of the Pickering particle layer. Read more

Later, stable oil in water emulsions were formed with hydrophilic Laponite RD® nanoparticles adsorbed at the interface of the oil phase and aqueous clay nanofluid in a T junction microfluidic chip. Emulsion stability up to at least 40 days could be observed. Read more