Fig. 3: Coupling to the bacterial flagellar motor.
From: An optically driven microstructure for torque measurement in rotary molecular motors
a Sketch of the experimental setup. A four-arm light-mill is attached to the motor through a 1.6 μm bead. b Trajectory in the x − y plane of an attached light-mill rotating around the flagellar motor axis at a radius r ≈ 1μm. c Instantaneous angular velocity ω as a function of the angle and for P = 0.32. The black dashed line represents a best-fitting curve as explained in the text. d Values of τ1/τ0 and τ4/τ0 (see Eq. (5)) as a function of power. e Orange dots plot the time-averaged rotational speed 〈ω〉 as a function of the laser power. Blue dots plot the angle-averaged speed \(\overline{\omega }\). The dashed green line is the expected curve if we assume that the motor torque is constant and equal to Tm = Tfree (estimated from the motor rotating a bead). The light-mill drag γ and the power to torque coefficient τ0 are those obtained from calibration performed before the light-mill was attached
