Gary Davies
Pickering emulsions were discovered over 100 years ago, and recently researchers have also discovered bijels and capillary suspensions. In these materials, colloidal particles are adsorbed to the interface between two immiscible liquids. Understanding the interaction between single particles and a liquid-liquid interface is crucial to our understanding of how such emulsions are stabilised.
Controlling the properties of colloidal particles in experiment is notoriously difficult. The ability to specify the contact-angle of spherical particles a priori is limited, particularly if one requires that all particles in a suspension are equally wettable. For anisotropic particles, ensuring that all particles have the same shape and wettability by the two liquids is a formidable challenge, and has non-trivial results for the stabilisation of emulsions and the dynamics of anisotropic particles at interfaces due to differing capillary and detachment forces.
Using a Shan-Chen lattice Boltzmann model with immersed extended rigid particles, it is possible to give spherical particles a well-defined arbitrary contact-angle. With our model, we investigated the detachment energy of spherical particles from liquid-liquid interfaces as a function of the particle contact-angle. We benchmarked our results against analytical solutions finding strong agreement. In so doing, we recovered a linear resistive force from the interface as predicted by de Gennes et al. Further, we simulated the detachment of prolate spheroids from an interface and determined their detachment energy as a function of aspect-ratio and wettability. Analytical solutions for the detachment of prolate spheroids are intractable due to the deformation of the three-phase contact-line.
In this presentation we compare the results of the detachment energy of prolate and oblate spheroids with those of spherical particles. The link between the dynamics of a single particle adsorbed to a liquid-liquid interface and the dynamics of emulsions and suspensions of many-particles will also be discussed.