Passive piezoelectric shunt control of an Atomic Force Microscope microcantilever

When operating an Atomic Force Microscope (AFM) in tapping mode the quality (Q) factor of the cantilever probe places a limitation on scan speed and image resolution. This paper introduces piezoelectric shunt control as a new method of controlling the Q factor of a piezoelectric AFM microcantilever. Using this method the mechanical damping of the cantilever is controlled by an electrical impedance placed in the oscillation circuit. It is shown that this control method is equivalent to a feedback system and standard control design techniques can be used to obtain the desired Q factor. A synthetic impedance was designed to allow easy modification of the control parameters in real-time. Control parameters were designed to minimize the Q factor of a commercially available AFM microcantilever and experimental results demonstrate a reduction in Q factor from 297.6 to 35.5, which is equivalent to a 13 dB reduction of the resonance peak.