(572g) Predicting Trajectories of Catalytically-Driven Self-Propelling Particles Under Geometric Asymmetries and Surface Heterogeneities

Colloidal particles can self-propel in response to various stimuli, including catalytic reactions, temperature gradients, and alternative AC fields. These particles have potential applications in areas such as drug delivery, self-healing materials, and delivery of chemical agents in porous media. While previous theoretical studies of self-propelling particles have mainly focused on predicting their translational and rotational velocities, collective behavior, and motion under confinement and non-Newtonian fluids, predicting the trajectories of self-propelling particles due to geometric and surface heterogeneities remains a significant gap in the literature.

In this talk, we will describe recent developments in our group's work on catalytically-driven particles, including:

(a) The motion of catalytic bent rods: Using slender-body theory, we derive the circular motion of bent-rods that self-propel due to catalytic reactions. We show that the relative arm length and angle between the two arms determine the radius of the circle and frequency of rotation, and we demonstrate how changing the angle between the arms in real time can be used to trace predefined trajectories.

(b) The effect of arbitrary interaction potential length-scale: Current literature estimates the translation and rotational velocity by integrating slip velocity over the surface, but this result is only valid in the limit of thin interaction lengthscale. To address this gap, we employ Lorentz reciprocal theorem and resistance-mobility formulations to derive concise expressions that predict the particle's translation and rotational velocities for arbitrary interaction potential. We demonstrate that the interaction potential length scale significantly affects the particle trajectories and that our approach overcomes some of the limitations of the widely used slip velocity approach.

(c) The impact of patch shape on catalytic spherical particles: Using non-axisymmetric spherical harmonic solutions and Lorentz reciprocal theorem, we obtain the trajectories of spherically catalytic particles with arbitrary-shaped patches. Our results reveal that particle trajectories are helical and that the patch shape affects the particle dynamics, which controls the pitch, radius, and orientation of the helical trajectories.

Relevant publications:

1. Ganguly & Gupta (2023). Physical Review Fluids
2. Roychowdhury, Ganguly, Gupta (2023), under preparation