Improving the engine power of a catalytic Janus-sphere micromotor by roughening its surface

Microspheres with catalytic caps have become a popular model system for studying self- propelled colloids. Existing experimental studies involve predominantly “smooth” particle surfaces. In this study we determine the effect of irregular surface deformations on the propulsive mechanism with a particular focus on speed. The particle surfaces were deformed prior to depositing a catalytic layer which resulted in the formation of nanoscopic pillars of catalyst. These features were shown to boost speed (~2×) when the underlying surface deformations are small (nanoscale), whilst large deformations afforded little difference despite a substantial apparent catalytic surface area. Colloids with deformed surfaces were more likely to display a mixture of rotational and translational propulsion than their “smooth” counterparts.