Position sensing and control of piezoelectric tubes for the atomic force microscope.

摘要

The Atomic Force Microscope (AFM) employes piezoelectric actuators for precise movements. Piezoelectrics have nonlinear properties such as hysteresis, creep, and nonlinear sensitivity that can distort AFM images. This dissertation presents a control system that uses sensing and feedback to reduce the effects of the piezo nonlinearity on images. An optical lever sensor was developed to measure the piezo's position by measuring the bending angle associated with the piezo's expansion. Using the sensor, a careful study of the piezo's behavior was made and a linear MIMO model was found. The model aided in design of controllers for tracking signals commonly used in AFM. The controllers were tested on a functioning AFM. Images of a calibration reference sample were taken with and without feedback. The image with position control had less distortion than the image without control.; The second part of the dissertation presents the development of an instrument for measuring protein-antibody binding using arrays of microcantilevers. The microcantilever deflect in response to surface strain caused by the selective binding of antibodies to a protein coating on the microcantilever. The instrument uses an automated scanning optical lever to measure the strain induced deflection of the microcantilevers.