An optical trap is calibrated by measuring the escape force for polystyrene beads and its dependence on laser power.
Rotation of E.coli attached with one flagellum to a glass substrate is used for the investigation of the flagellar motor.
The torque excerted by the flagellar motor is determined in two ways:
- The angular velocity is measured, knowing the friction of the surrounding medium.
- The escape force for rotational motion is measured with optical tweezers.