Investigation on Surface Forces Measurement Using Force-Balanced MEMS Sensor

In order to avoid the displacement of the AFM cantilever in surface forces measurement, a force-balanced MEMS sensor is developed. The probe of the sensor is a pendulous micromachined sensing element, which can be considered as a pair of differential capacitors. When the sensor is designed as a closed-loop system, the electrostatic force feedback can balance the surface force supplied on the sensing probe, and maintain the pendulum of the probe at the balance position. Consequently, when using the force-balanced MEMS sensor, the surface force between two surfaces can be measured with precisely controlled distance, and the displacement of the conventional cantilever is avoided. Experiment on surface force measurement between the pendulum surface of the probe and a ball´s surface is performed, as the distance between the two surfaces is controlled by a nanopositioner.