AFM technique development

In order to successfully explore our interest in the effect of surface properties on amyloid formation using AFM, full understanding of tip/sample interactions and technique development are crucial. As a result of this necessity, we are modeling in situ tapping mode AFM with numerical simulations to develop new ways of exploring surface properties. Our AFM model contains a feedback loop equipped with an integral and proportional gain allowing for the simulation of complete tapping modeAFM experiments with the cantilever imaging different types of surfaces with a range of morphologies and properties. Simulation can be carried out to explore the role of various imaging parameters (i.e. gains, scanning rates, operating frequencies, Q, and sample properties among others) on imaging stability and tip/sample forces.

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Understanding these dynamics has proven invaluable in the development scanning probe acceleration microscopy (SPAM) and will be applied to further innovation in the scanning probe field. SPAM makes it possible, for the first time, to reconstruct the tip/sample force during each individual tapping event in a tapping-mode AFMexperiment in fluids. Such tip/sample force interactions contain information about surface mechanical properties, such as modulus and adhesion. The ability to extract such information during a standard AFM experiment makes it possible to study—with nanoscale spatial resolution in real time—changes in these properties in response to environmental factors (e.g., pH, temperature, salt concentration). Since this technique can be applied in solution, it has enormous potential to probe biologically relevant problems, such as changes in the modulus of bilayers, cells, and other biological surfaces under the influence of external factors (e.g., cholesterol content and structure-modifying drugs).

Figure: The underlying principle behind scanning probe acceleration microscopy.