US Patent 7367242 Active sensor for micro force measurement

An active micro-force sensor is provided for use on a micromanipulation device. The active micro-force sensor includes a cantilever structure having an actuator layer of piezoelectric material and a sensing layer of piezoelectric material bonded together. When an external force is exerted on the sensor, the sensor deforms and an applied force signal is recorded by the sensing layer. The applied force signal is then fed back to the actuating layer of the sensor via a servoed transfer function or servo controller, so that a counteracting deformation can be generated by the bending moment from the servoed actuating layer to quickly balance the deformation caused by the external micro-force. Once balanced, the sensor beam comes back to straight status and the tip will remain in its equilibrium position, thus the sensor stiffness seems to be virtually improved so that the accurate motion control of the sensor tip can be reached, especially, at the same time, the micro-force can also be obtained by solving the counteracting balance voltage applied to the actuating layer.