Collaborative Research: Structure and Dynamics of Liquid Interfaces Studied by X-Ray and Neutron Scattering

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Non-Technical AbstractMuch of the biological activity of cells takes place on membranes. Consequently, a focus of research on biosensors is the construction of artificial membranes supported on semiconductor surfaces. The goal of the present work is to investigate the structural and dynamic properties of such supported membranes using a sophisticated technique known as coherent x-ray scattering. The results of measurements will be used to construct hydrodynamic models of membrane motion and to determine the values of important physical parameters such as the surface tension, viscosity and elastic moduli. The research will begin on lipid bilayers supported on a substrate and probe the changes in their dynamics as membranes are freed from the substrate by adding intermediate cushioning layers such as cellulose films, or by tethering the membranes above the substrate with proteins. The results of this research will have significant impact on the application of polymer films in composites, adhesives, packaging, biocompatible materials, and biosensors. Students, including from underrepresented groups, will be trained in the use of state-or-the-art synchrotron x-ray facilities at national laboratories.Technical AbstractThis project will study the structure and dynamics of liquid interfaces including both polymeric fluid interfaces and lipid bilayers using grazing incidence x-ray scattering and x-ray Photon Correlation Spectroscopy (XPCS) which utilizes coherent x-ray beams. Coupled with theoretical treatments of viscoelastic hydrodynamics, this work will provide methods of analyzing the interface tension, viscosity and elastic moduli of thin liquid films. Anomalous dynamical behavior in the vicinity of the glass transition temperature for polymeric films will be examined. The work on polymers will provide the starting point for studies of the dynamical fluctuations in lipid bilayer membrane systems. Supported membranes in water on bare or cushioned substrates provide oriented films of sufficient surface area to study with techniques such as x-ray or neutron scattering, XPCS or neutron spin echo. The structure, conformation and dynamics of these layered systems will be studied to elucidate the viscosities and elastic moduli of membranes under various conditions. The results of this research will have significant impact on the application of polymer films in composites, adhesives, packaging, biocompatible materials, and biosensors. Students, including from underrepresented groups, will be trained in the use of state-or-the-art synchrotron x-ray facilities at national laboratories.