(27a) Anisotropic Particle Interactions with Surfaces, Other Particles, and External Fields

Anisotropic colloidal particles are present in numerous natural and synthetic materials that are important to environmental, biological, and advanced material applications. Interactions of anisotropic particles with each other, surfaces, and external fields determines all of their behavior and properties. As such, it is essential to have physically realistic accurate models of anisotropic particle interactions to design, control, and optimize their behavior and properties in applications. In this work, we report closed-form analytical potentials for anisotropic particle interactions, which we also measure on the kT-scale via optical microscopy experiments. First, we present an interaction potential for arbitrarily oriented convex anisotropic particles with planar surfaces using DLVO half-space interactions in combination with the Derjaguin approximation. A relatively simple potential is obtained for all particles that can be described by the super-ellipsoid equation, which includes spheres, ellipsoids, cylinders, polygons, super-spheres, as well as many other shapes. We extend the analysis of particle-wall potentials to determine pair potentials between arbitrarily oriented anisotropic particles. Next, we report dipole-field and dipole-dipole potentials for super-ellipsoidal particles in AC electric fields. We demonstrate the validity of these potentials through measurements of single particles and quasi-2D phase behavior in combination with an inverse Monte Carlo analysis. Finally, we show that tuning electric field mediated potentials can be used to manipulate position, orientation, and assembly of super-ellipsoidal colloidal particles.