ENGINEERING RESEARCH EQUIPMENT: A Combined Fluorescence Optical Microscope/Non-Contact Atomic Force Microscope for Monolayer and Multilayer Studies

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9622506 Zasadzinski New modes of imaging with scanning probe microscopes - non-contact, tapping, and friction or lateral force modes - have made it possible to image a variety of surfaces that had previously been difficult or impossible to OseeO. These new imaging modes take advantage of variations in surface chemistry, friction, compliance, charge, etc. to develop image contrast in addition to simple surface topography. For many of these modes, the AFM tip is either not in contact with or is gently tapped on the sample surface. Hence, much softer surfaces can be imaged than with conventional contact mode AFM and there is less tendency to rearrange loosely supported materials. It is proposed to upgrade the current contact mode AFM by purchasing a Nanoscope Multimode AFM and the necessary accessories to do non-contact and tapping mode imaging. These new imaging modalities will be applied to the ongoing studies of self-assembly and pattern formation in surfactant, lipid and proteins. These new imaging modes are proving to be extremely useful in examining complex fluid interfaces, surfactant, protein, and polymer adsorption, lateral phase separation in membranes, protein localization and diffusion, the kinetics and structures of self-assembled films, etc. This new apparatus will also allow us to characterize more realistic model membrane surfaces for force measurements with the Surface Forces Apparatus. To fully implement the new imaging modes, it is necessary to identify areas of interest on the surface prior to engaging the AFM. The best way to do this is by coupling the AFM to a high resolution optical microscope capable of fluorescence imaging. Fluorescence microscopy is one of the best ways of identifying lipid domains, specific proteins (via antibody labeling), adsorption etc. at the micron level. It would be a major advance to directly correlate the fluorescence images with molecular resolution AFM images. A custom fluorescence microscope has recently been built for examin ing monolayers at the air-water interface. A very similar instrument can be constructed to examine thin films on substrates prior to and during AFM imaging. With this combined capability, the principal investigator should be able to localize proteins, phase boundaries, etc. and correlate them with their macroscopic effects on bilayer properties. The transfer of the spontaneous patterns formed by various lipid mixtures at the air-water interface to substrates to be used as lithographic-style templates, the patterns formed by competitive self-assembly of mixtures of adsorbing species, and the initial stages of mineralization of surfaces, can also be studied. ***