Shape-anisotropic particles at curved fluid interfaces and role of Laplace pressure: a computational study

The self-assembly behavior of shape-anisotropic particles at curved fluid interfaces is computationally investigated by diffuse interface field approach (DIFA). A Gibbs-Duhem-type thermodynamic formalism is introduced to treat heterogeneous pressure within the phenomenological model, in agreement with Young-Laplace equation. Computer simulations are performed to study the effects of capillary forces (interfacial tension and Laplace pressure) on particle self-assembly at fluid interfaces in various two-dimensional cases. For isolated particles, it is found that the equilibrium liquid interface remains circular and particles of different shapes do not disturb the homogeneous curvature of liquid interface, while the equilibrium position, orientation and stability of a particle at the liquid interface depend on its shape and initial location with respect to the liquid interface. For interacting particles, the curvature of local liquid interfaces is different from the apparent curvature of the particle shell; nevertheless, irrespective of the particle shapes, a particle-coated droplet always tends to deform into a circular morphology under positive Laplace pressure, loses mechanical stability and collapses under negative Laplace pressure, while adapts to any morphology and stays in neutral equilibrium under zero Laplace pressure. Finally, the collective behaviors of particles and Laplace pressure evolution in bicontinuous interfacially jammed emulsion gels (bijels) are investigated.