Fig. 4

Light-switchable rotation of a Si nanowire stepper motor. a, b Rotation angle versus time of a nanowire at different voltages (or electric field strengths) exposed to 318 mW cm⁻² 532-nm laser. a The E-field rotates at 1.49 Hz (in green). The stepper motor rotates synchronously with the E-field with a phase lag θ, at 20 Vpp (400V cm⁻¹) (in orange). Inset: the constant phase lag between the driving E-field and the rotating nanowire. b It switches to the out-phase oscillation mode at 12 Vpp (240 V cm⁻¹) (more details in Supplementary Note 7 and Supplementary Figs. 3, 4). Schematics show the relative positions of a rotating nanowire with the E-field at different time. c Average rotation speed of a micromotor versus driving voltage/electric field strength with (in blue) and without laser illumination (in orange). The driving E-field is 1.49 Hz, same as that the in-phase rotation of the nanowire (see Supplementary Movies 4, 5 for the curve in blue). d Average rotation speed of a micromotor versus rotation speed of the driving E-field at 30 Vpp (600 V cm⁻¹) with (in blue) and without laser illumination (in orange) (see Supplementary Movies 6, 7 for the curve in blue).