Development of Material Characterization Techniques using Novel Nanoindendation Approaches on Hard and Soft Materials used in MEMS

Investigating and modeling the mechanical properties of materials is important for many applications. The most common technique used for mechanical characterization of materials is called nanoindentation. The currently available tools utilized in order to perform nanoindentation have their limitations in terms of sensitivities in force and displacement for a broad range of material properties. When it comes to investigation of soft materials, these limitations might be more detrimental. In this dissertation work, novel nanoindentation techniques have been developed with a multi-probe scanning force microscopy (SPM) system in order to ease the major problems encountered with standard Atomic Force Microscopy (AFM) or nanoindentation systems. Tuning forks are used as probes during nanoindentation. By using the newly developed nanoindentation techniques for quasi-static nanoindentation experiments, the force information is extracted through the displacement of the indenter probe measured by a second probe with ultraresolution. For dynamic nanoindentation, frequency modulation techniques have been used to extract force information from a single indenter tuningfork probe. Thanks to the high quality of resonance (Q factor) of tuning fork probes, force measurements can be performed with an ultra high resolution. The accurate measurements of material properties on soft materials is used in characterization of microfabricated pillar sensors which can be used in measuring nN level of cell traction forces in a biomedical application. The techniques developed in this research also enable the system as an ultra-sensitive force sensor to apply nN scale lateral and vertical loads on microfabricated structures or biological specimens.