Structurally Dependent Self-Propulsion Behaviors of Pt-SiO₂ Micromotors

The structural dependence of self-propelled motion in micro/nanomotors is essential for effectively predicting and controlling their dynamic behaviors. In this study, platinum-silica (Pt-SiO₂) micromotors, with structures ranging from spherical Janus to dimer configurations, are fabricated through conventional template-assisted deposition, followed by annealing. These structures are used to investigate how geometry influences motion. Our results demonstrate that the architecture of the Pt-SiO₂ micromotor strongly affects its propulsion mode and trajectory in solution. When immersed in a hydrogen peroxide (H₂O₂) solution, spherical Janus Pt-SiO₂ micromotors exhibit quasi-linear motion, driven by the Pt side (Pt pushing). In contrast, dimeric structures and intermediate forms varied from Janus to dimer display quasi-circular trajectories with continuously changing directions, characteristic of Pt-dragging motion. We reveal that these distinct propulsion behaviors stem from differences in the spatial distribution of Pt on the SiO₂ sphere surface. Variations in Pt distribution alter the exposed silica surface area-rich in hydroxyl groups-which modulates the driving force and causes the resultant force acting on the micromotor to deviate from its mass center axis (or the axis connecting the mass centers of the Pt component and silica sphere), thereby inducing circular motion. This study offers a versatile strategy for fabricating Pt-SiO₂ micromotors with tailored structures and advances the fundamental understanding of structure-dependent self-propulsion mechanisms.