Kausik Das

Thesis Advisor: Dr. Ali Nadim (Claremont Graduate University - Institute of Mathematical Sciences)

Second Reader: Dr. Maria Cameron (University of Maryland - Department of Mathematics)

Contact: kdas@hmc.edu

Modeling self-diffusiophoretic Janus particles in fluid

We explore spherical Janus particles in which a chemical reaction occurs on one face, depleting a substrate in the suspending fluid, while no reaction occurs on the other face. The steady state concentration field is governed by Laplace’s equation with mixed boundary conditions. We use the collocation method to obtain numerical solutions to the equation in spherical coordinates. The asymmetry of the reaction gives rise to a slip velocity that causes the particle to move spontaneously in the fluid through a process known as self-diffusiophoresis. Using the Lorentz reciprocal theorem, we obtain the swimming velocity of the particle. We extend the results to Janus particles with arbitrary surface coverage, maximizing the swimming velocity as a function of the size of the reaction site.