The atomic force microscope (AFM) is an instrument that allows the interrogation and manipulation of matter at the atomic scale and has revolutionized science and engineering. AFM based nano-interrogation includes, topographic imaging where one is interested in recreating an image of a sample, and material characterization where one wishes to determine intrinsic material properties. The primary drawback of AFMs is their low speed especially when interrogating soft matter, e.g., polymers and biological samples. This research involves the study of advanced signal processing algorithms that will allow simultaneous topographic imaging and materials characterization at ultra-high speeds and high fidelity. This will significantly accelerate the knowledge discovery process in domains such as material science, where the focus is often on fast evaluation of new materials. The investigator will promote cross-fertilization of ideas between the signal processing and the AFM communities by organizing joint workshops. The findings will be integrated into the curriculum via lab components and modules.
The AFM uses a cantilever with a sharp tip that deflects based on inter-atomic forces; interrogation is performed by sensing and interpreting this deflection signal. This research focuses on the dynamic mode operation (the preferred mode for interrogating soft material), where the cantilever is typically excited sinusoidally and gently taps the medium. Current methods work by analyzing the steady state cantilever trajectory and are fundamentally limited in speed by the time-constants of the cantilever dynamics. This research will study order-of-magnitude improvements in speed by leveraging (a) the systems viewpoint and (b) newer AFM techniques such as multi-frequency excitation. Signal processing algorithms for simultaneously detecting topographic features and/or material property changes will be studied and exhaustively tested on experimental data.
