Fig. S5.

Motor speed is independent of laser intensity. (A–C) Motor speed for gold beads attached to Na⁺ motors (black) and laser power (red) verus time, showing that the motor speed is not affected by the laser light on a timescale of minutes. For B and C, laser power was adjusted by hand by rotating a half-wave plate. Increasing laser power shows no obvious effect on motor speed. (D) Motor speed versus laser power measured over six motors, each recorded for 400–800 s, including the motors shown in B and C. The speed of an additional 25 motors was observed in real time but not recorded, as laser power was varied; these motors showed a similar independence of motor speed on laser power. Laser intensity was measured in arbitrary units (a.u.) via the voltage of the QPD; a laser intensity of ∼1 a.u. was used for low-load gold bead experiments.