Tailoring the Propulsion Dynamics of Rod-Shaped Colloidal Micromotors Driven by Passive Particles

Studying the interactions among the active and passive units in a heterogeneous fluid medium is an attractive regime in active matter systems. It is of paramount importance to investigate those systems not only to understand the complex dynamics behavior but also to design reconfigurable novel structures. Here, the light-activated rod-like colloidal micromotors show intriguing swimming patterns when attached to inert silica spheres. The active colloidal systems comprise rod-like swimmers made of semiconducting material like silica-titania, fabricated primarily by the Glancing Angle Deposition (GLAD)-based Physical Vapor Deposition (PVD) technique. The activity of the rods is solely triggered upon UV illumination, resulting in phoretic slip flows around the rods, which push them into a translational swimming mode. Interestingly, their swimming behavior changes upon encountering passive silica particles, transitioning from an inherent random path to spiral, linear, or orbital patterns depending on the number and size of the attached particles. Numerical modeling is also performed, which accurately predicts these behaviors, aligning with experimental results. This study not only advances the ability to control active particle behavior in inert colloidal fluid mediums but also enhances the understanding of similar cumbersome phenomena in other biological and artificial nonequilibrium systems.