Fig. 1

Tori with two types of surface coating. a A High-resolution transmission electron microscope (STEM) image of “glazed” Janus torus on a carbon lacey TEM grid. The metallic cap has been applied to the top of the tori. The scale bar is 3 μm. b SEM image of a “dipped” Janus tori on a carbon TEM grid. The bottom of the torus is “cut off” at the bottom to provide a stable base during printing and the metal evporation. The scale bar is 2.25 μm. c A graph representing the propulsion velocity dependence on the concentration of hydrogen peroxide. Red and orange horizontal bars are respectively the propulsion velocities glazed and dipped tori (with 40 nm Ni and 10 nm Pt) on a gold substrate at 0% H₂0₂. Green and yellow squares are respectively the propulsion velocities glazed and dipped tori (with 40 nm Ni and 10 nm Pt) on a gold substrate at 5% H₂0₂. Dark green diamond is the propusion velocity of glazed tori (with 40 nm Ni and 10 nm Pt)on a glass substrate at at 10% H₂0₂; and comparitively,teal diamond is the propulsion velocity of dipped tori (with 40 nm Ni and 10 nm Pt) on a gold substrate at 10% H₂0₂. Purple and dark blue triangles are, respectively, the propulsion velocities glazed (with 40 nm Ni and 10 nm Pt) and dipped tori (with 10 nm Ni and 40 nm Pt) on a gold substrate at 15% H₂0₂. Magenta, lime, and ice blue circles are the propulsion velocity of 3 μm diamater glazed tori, 7 μm glazed tori, and 7 μm dipped tori at 30% H₂0₂. The three tori have a coating of 40 nm Ni and 10 nm Pt. A full legend can be found in Supplementary Fig. 3 and in Supplementary Note 2. The error bars represent a unique standard deviation for that particular sample