(550h) Fundamentals of the Fluid Particle Dynamics Method for Simulating the Chemohydrodynamics of Passive and Active Colloids

There has been tremendous interest in recent years in the transport of colloidal particles driven by concentration gradients. For example, chemically active colloids can modify the concentration field of its surrounding, thus harvesting energy from the environment to self-propel and/or change the trajectory of neighboring colloids. Passive colloids can also migrate in response to a solute concentration gradient, a phenomenon known as diffusiophoresis. In either case, hydrodynamic interactions are also critical for accurately modeling systems of colloidal particles. To date, the most efficient methods to simulate chemohydrodynamics rely on Green's functions for the Laplace and Stokes operators that are only valid in the steady and dilute limits. However, many systems of interest display interesting behavior where these limits do not apply. The Fluid Particle Dynamics (FPD) method developed by Tanaka et al. is an interesting alternative that has the potential to efficiently and accurate simulate the full chemohydrodynamics of passive and active particles. We demonstrate the feasibility of this approach by simulating diffusiophoresis of colloidal particles, which compare favorably to known theories. We also demonstrate the capacity of the method to simulate self-diffusiophoresis by adding asymmetric chemical reactions to colloidal systems. Finally, we explore the computational and phenomenological limits of the method by simulating multi-particle phoretic motion coupled to complex concentration fields.