Fig. 4

High-resolution scanning transmission electron microscopy (STEM) micrographs. a An image of the swimming orientation for tori with 40 nm nickel and 10 nm platinum. The Janus glazed  tori rest with their polymer structure near the substrate, and the patchy tori swim platinum-leading face forward. b A secondary-electron STEM image focused on the cross section of a single layer in the 3D printed structure. The scale bar is 3.25 μm. c A secondary-electron STEM image of the different materials deposited on separate layers of the tori. The nickel forms a smooth structure while the platinum nucleates into droplets on the binding layer. The scale bar is 300 nm. d A bright-field image of platinum contamination (in white) on the first polymer layer in the tori. The platinum contamination is responsible for an enhanced conductivity on the surface of the polymer. The scale bar is 200 nm. e A dark-field image of the platinum droplets on the uniform nickel binding layer. The platinum formed droplets \(\sim\)20 nm in diameter. The scale bar is 100 nm. f An image of the swimming orientation for tori with 10 nm nickel and 40 nm platinum. The Janus tori rest with their metal cap near the substrate, and the patchy tori swim polymer-leading. g Cross-sectioned, dark-field image of a tori coated in 10 in nickel and 40 nm platinum. We see a clear separation between the carbon polymer, nickel binding layer, and catalytic platinum layer. The scale bar is 700 nm. h A close-up, dark-field image at the interfaces between platinum and and nickel. We observe a smooth platinum layer ~200 nm thick. i Secondary-electron imaging (on STEM) of the smooth platinum layer. The platinum layer covered almost entirely the nickel binding layer. The scale bar is 200 nm