Figure 1: Ribbons of dipolar Janus rods at zero magnetic field.

(a) Representative optical image of a concentrated suspension of the dipolar Janus rods. The image includes some solitary uncoated particles, which do not interfere with the dipolar assembly. Scale bar, 5 μm. Inset: representative scanning electron microscopy image of individual rods with schematic representation, in which blue represents the nickel-coated side and white the bare silica side. Scale bar, 0.5 μm. (b) Liquid-crystal-like deformation modes of a colloidal ribbon, images accompanied by schematic illustrations. For clarity, the Janus feature is not illustrated. Scale bar, 2 μm. (c) End-on view of a ribbon in a small vertical field (1.6 G), accompanied by schematic illustrations highlighting the trans and cis bonds. Yellow arrows denote the dipole moment of each rod. Red lines highlight trans and cis bonds. Scale bar, 2 μm.