Fig. 3: Friction anisotropy on MoS₂.

a Ratios of friction forces (see Methods) recorded on SiO₂ and MoS₂, as a function of rotation angle, extracted from a scan of 8 µm × 8 µm in size. Periodic behavior with nearly twofold symmetry is observed. b Friction force recorded on MoS₂ as a function of rotation angle, extracted from a scan of 50 nm × 50 nm in size. Periodic behavior with nearly fourfold symmetry is observed. c Friction force recorded on MoS₂ as a function of rotation angle, extracted from a scan of 1.5 µm × 1.5 µm in size, showing non-periodic character. Error bars represent standard deviations.