Analysis of thermal drift in atomic force microscopy and design of compensating MEMS-based micro-stage

Abstract

Single-molecule force spectroscopy has become a powerful research area. The most commonly used single-molecule force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy (AFM). For accuracy of the experiments in all three techniques, the ability to measure the position of the probe is critical. Thermal drift in the experimental setup is detrimental for the stability and accuracy of measurements. Temperature uctuation in an AFM setup causes cantilever de ection. For long time scale experiments in AFM, ambient temperature stability becomes the main concern as AFM cantilever is usually a bimaterial structure and sensitive to temperature gradient. Thermal drift in AFM can be harmful for biomolecules anchored between a cantilever and a stationary sample surface as the force on the molecules increases if the cantilever de ects towards the surface. In addition, thermally induced de ection causes false force readings and a shift in zero-force level. In this thesis, the analysis of thermal drift in AFM cantilevers by thermal drift modeling and experimental characterization of the thermal drift in AFM cantilever is reported. With MEMS technology, various thermomechanically matched micro-stages in order to compensate the thermal drift in AFM cantilevers are designed. Lastly, fabrication process for the MEMS micro-stages, which is a 3-mask process, is developed.