Adhesive and Mechanical Behavior of Short Molecules

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Molecular self-assembled monolayers (SAMs) are highly organized surface films, one molecule (2-3 nm) thick, composed of short organic molecules which assemble like stalks of wheat on a wheat field. They govern the structure and mechanical and adhesive behavior of the films. SAMs are important for a wide range of engineered systems, from adhesives to micromachine lubricants to nanolithography and nanostructured devices and materials. In all cases, the adhesive, frictional and mechanical behavior must be understood for the design of systems that make use of SAMs However, very little is known about this behavior, particularly under combined loadings.The hypothesis for this study is that the mechanical behavior of SAMs may be obtained from molecular analyses of relatively simple stress states and used in continuum analyses of more complex stress states that arise in nanoindentation experiments and in the growing array of SAM-based materials systems and structures. This hypothesis will be examined for several different SAMs and surfaces using molecular analyses of a broader range of simple characterizing stress states and time scales, and normal indentation experiments coupled with tangential loading using interfacial force microscope probes.The project will provide broadly trained students who will be productive working in interdisciplinary environments at universities or in industry. One undergraduate student will also be incorporated in the project. Texas demographics are such that the undergraduate body at UT-Austin has a significant Hispanic representation (~20% in the ASE Department), who we successfully encourage to participate in our undergraduate outreach programs.