Interfacial Configurations of Lens-Shaped Particles

We study the configuration behaviors of non-spherical lens-shaped particles at a fluid-fluid interface. The attachment energies of truncated spheres and biconvex particles are calculated numerically to determine the thermodynamically stable configuration of the particles at the interface. When the particle is rotated 180° perpendicular to the interface, two energy minima are observed in the attachment energy profile. One corresponds to equilibrium and the other to a metastable orientation. The high energy barrier between the two energy minima indicates that the particle with the metastable condition is not spontaneously converted to the equilibrium state, such that the interface adsorption and orientation behaviors of the particles are irreversible and are determined stochastically. A further comprehensive investigation of the interfacial pinning phenomena of the truncated or biconvex boundary and free-rotation of the particles is also performed for different wettability and geometric factors. This study offers simple design rules for the synthesis of anisotropic particles used as a solid surfactant.