# Structurally Dependent Self-Propulsion Behaviors of Pt-SiO2 Micromotors

## TL;DR

This paper explores how the shape of Pt-SiO2 micromotors affects their movement in solution, revealing how structural changes influence propulsion behavior.

## Contribution

The study introduces a fabrication method for Pt-SiO2 micromotors and reveals how Pt distribution affects propulsion modes.

## Key findings

- Spherical Janus Pt-SiO2 micromotors show quasi-linear motion in hydrogen peroxide solutions.
- Dimeric and intermediate Pt-SiO2 structures exhibit quasi-circular motion due to Pt-dragging behavior.
- Pt distribution on the SiO2 surface modulates propulsion by altering the driving force direction.

## Abstract

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.