Collaborative Research: Intentionally Nonlinear Design of High-frequency Atomic Force Microscopy for Enhanced Material Characterization

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Since its development in the early 1980s, atomic force microscopy (AFM) has been one of the most useful imaging tools in the fields of nano- and biosciences. This award supports theoretical and experimental studies of a new type of AFM realized through constructive use of intentional nonlinear resonance enabling the utilization of high-frequency measurements for sensing. Apart from proving the efficacy of the concept of constructive utilization of intentional nonlinearity in nano/micro designs to achieve performance not otherwise attainable, in a broader sense this project's approach can act as a testbed for assessing how strong nonlinearity incorporated into a complex mechanical system can lead to drastic performance gains. This work can be potentially transformative, since it can provide a new paradigm of intentionally nonlinear AFM technology based on higher-frequency sensing, with demonstrated capacity for drastically enhanced sensitivity and performance. The gained AFM sensing capability will be an incomparable tool in fields such as nano- and bio-sciences.Detailed analytical, computational and experimental studies will be performed of a new, microcantilever beam design enabling higher-frequency nonlinear AFM. Under dynamic mode operation an intentionally designed 1:n internal resonance between the two leading bending modes of the AFM microcantilever incorporating an inner Silicon paddle, leads to magnification of high-frequency harmonics in the paddle response, which is the basis for AFM of improved sensitivity. The research team will develop the significantly enhanced AFM measurements of sample material properties and topography, achieved through sensing of higher harmonics in the response. The research team will systematically study, optimize, extend and validate this promising concept through theoretical studies to characterize the paddle's response to different types of interaction forces, and will perform an extended series of experimental tests to assess the sensitivity of high-order internal resonance designs to changes in topology and material properties. Moreover, multi-paddle AFM designs incorporating multiple simultaneous internal resonances will be analyzed for quantitative characterization, whereas related microfabrication issues will also be addressed.