Dielectrophoretic measurement of bacterial motor characteristics

Two methods of measuring bacterial motor characteristics using AC field effects in a microfabricated electrode system are presented. One is the measurement of the external force-velocity characteristics (F-v) of swimming bacteria. Electrostatic orientation of bacteria parallel to the field lines is used to guide the bacterial locomotion along a line. Dielectrophoresis is used to apply an external force, either forward or backward, to the swimming bacteria, and the velocity of locomotion is measured to obtain the F-v curve. The other approach is to measure torque-speed characteristics (T-w) of the motor. Electrorotation is used to apply external torque to the tethered cells, and by changing the applied torque and measuring the rotation speed, the T-ω curve is obtained. The results show that the motor generates approximately constant torque in the measured range of ω (0-100 Hz), regardless of the direction of rotation