Great advances in scientific discovery and human progress have often followed the development of new scientific tools that allow us to "see" well beyond our everyday experience. The Atomic Force Microscope (AFM) is one such tool that has revolutionized materials science by its ability to visualize a wide variety of materials under different conditions with the resolution of an atom. In the past, AFM has been used to render contrast at one frequency but these days it is possible to observe multi-spectral contrast in images at many different frequencies: in effect like an optical microscope being able to observe contrast through different filters. This research project will allow Purdue University researchers to work closely with an industrial partner, Oxford Instruments-Asylum. The team will innovate methods to convert this multi-spectral contrast to quantitative physical properties to help in the design and discovery of next-generation materials for biomedical, energy storage, and consumer products. A comprehensive theoretical and experimental research and outreach program is planned to significantly advance the state-of-the art of multi-frequency AFM through a collaboration between Purdue University, Oxford Instruments-Asylum, a leader in the multi-frequency AFM market, and KTH, Sweden. The project also involves development of new courses in polymer interactions and multi-frequency AFM for students and enhancement of Virtual Environment for Dynamic AFM capability for multi-frequency AFM operation for polymers which will greatly benefit students and other researchers.
The most important multi-frequency Atomic Force Microscopy modes today can be conceptually understood as nonlinear systems with slow and fast timescale dynamics. This project will undertake analytical perturbative, continuation, and experimental approaches to analyze these problems to yield a rich harvest of predictive insight into microcantilever motions, stability, bifurcations, and chaos. On one hand, this information will help operate multi-frequency AFM's in stable regimes, while on the other hand, the insight will help guide the operating conditions most appropriate to generate contrast on a specific material. Additionally, sophisticated computational tools and experimental validation will allow an unprecedented correlation between experimental observables in multi-frequency Atomic Force Microscopy and the local properties of soft polymeric materials used in electronics, biomedical devices, and consumer products. These tools will be made available to hundreds of researchers worldwide through the software suite Virtual Environment for Dynamic Atomic Force Microscopy on the cyber-infrastructure of nano-HUB. The work is a comprehensive study of the dynamical foundations of multi-frequency AFM, a next emerging frontier in the evolution of Atomic Force Microscope towards a truly functional, quantitative nanoscale imaging technology. The findings will be transferred to industry through the close collaboration with Oxford Instruments (Asylum). While the focus of the project is on multifrequency Atomic Force Microscopy, there is a clear trend towards multiple frequency methods across many imaging technologies; for example, in contrast enhanced ultrasound, electrical impedance tomography, and microwave imaging to name a few. Thus the approaches developed in this work could not only spill over to multi-frequency imaging methods in other biomedical or materials instrumentation but could also create opportunities for multi-spectral monitoring in micro- and nano-electromechanical systems.
