The goal of this project is to simultaneously map the mechanical properties, and characterize the structure, of a biological sample using a scanning probe microscope (SPM). The main part of the SPM is a cantilever, that may be visualized as a miniature diving board with a sharp tip attached to the underside of the free end. The fixed end of the cantilever is moved up and down in a controlled way, as a sample is passed under the sharp tip. The challenge addressed by this project is to infer both the surface topography and the mechanical properties of the sample from the way the cantilever bends as it is moved up and down, and the sample moves beneath it. Extracting this data is challenging, because it can be difficult to separate the influences of the different components of the forces exerted by the moving surface. Use of the SPM on biological materials is further complicated by operational limits needed to avoid damaging delicate samples, and by the need to sometimes characterize samples in a liquid environment. This project considers how the excitation motion may be adjusted based on the cantilever response to provide the best possible measurement. Changes in mechanical properties of biological samples have been related to the progression of numerous diseases, including fibrosis, cancer initiation and metastasis. The ability to reliably measure these properties will advance diagnostic tests for these conditions. The project includes outreach to middle- and high-school students through tours and presentations under well-established programs at Iowa State University.
This project aims to improve the performance and build new functions of scanning probe microscopes (SPM) in poro- and visco- elasticity mapping of a broad variety of biological materials, using control-based approaches. The specific objectives are to (1) formulate a nanomechanical characterization methodology with optimal excitation force design to enable excitation of sample visco- and poro- elastic behavior; (2) build a new control-based adaptive SPM imaging technique with sample deformation quantification and real time force and speed optimization based on optimal output transition design; (3) achieve high-speed nanomechanical property mapping through formulating new data-driven inversion-based control approach to compensate for dynamics coupling and system uncertainty; and (4) implement and evaluate the nanomechanical property mapping scheme on SPM and then to develop an integrated software platform to synchronize the SPM mapping with optical-based bio-structure quantification.
