Active colloidal particles differ from Brownian particles because they convert external energy, such as light, electric fields, magnetic fields, or chemical reactions, into directed motion. Here we characterize how the Janus balance and aspect ratio of active colloidal particles affect their propulsion dynamics. In this study, we synthesized 4μm spherical polystyrene (PS) active particles with varying platinum (Pt) coatings by embedding them in polyvinyl alcohol (PVA) films of different thicknesses. Due to partial embedding, particles in thicker films received a smaller amount of Pt coating when a deposition process was applied, whereas those in thinner films received more; these differences are characterized by scanning electron microscopy. This method was applied to spheres and two types of anisotropic active particles: end-coated ellipsoids and éclair-shaped ellipsoids. Image sequences taken by confocal laser scanning microscopy (CLSM) revealed that end-coated ellipsoid particles tended exhibited ballistic trajectories, whereas éclair-shaped ellipsoids preferentially followed helical paths, suggesting that variations in Pt-coated regions significantly impact propulsion behavior. These trajectories were identified in the two-dimensional propulsion profiles by distinguishing between the linear profile of the ballistic trajectory and the sinusoidal profile of the helical trajectory. To further investigate the effect of Janus balance and aspect ratio on active particle motion, we designed a molecular dynamics (MD) simulation framework to model ellipsoidal active particles with asymmetric distributions of Pt. We constructed coarse-grained ellipsoidal particles and divided their surfaces into 32 sub-regions. By selectively activating 2 to 5 adjacent sub-surfaces, we generated 28 distinct active configurations. The resulting simulation library provides a systematic correlation between the active region distribution and the propulsive trajectories of the particles. This simulation-based approach can serve as a valuable tool for guiding experimental studies, because synthesizing highly asymmetric Janus coatings and tracking their motion in real experiments pose significant challenges. The MD simulations therefore enhance understanding of active particle propulsion mechanisms and inform the design of tailored synthetic strategies for future applications in self-propelled colloidal systems.
