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Hans-Georg Braun
Surface and interface engineering
Previous and current research
Understanding and tuning the interaction of biological entities with material surfaces is one goal of Molecular Bioengineering.
From the material science point of view surface engineering contributes significantly to this objective. As part of the surface engineering approach our work focuses on the realization of chemical microheterogeneous surfaces with lateral patterns in between 100 nm and several 10 µm.
As one major topic we study the influence of chemical heterogenities on structure formation of liquid phases in contact with the micropatterned surfaces. The spatial control of liquid phases on microstructured surfaces offers an promising route to realize planar microfluidic structures and to design microstructured fluid environments acting as containments for chemical and biochemical reactions as well as confinements for self-organization processes.
The experimental tools for surface patterning include soft lithography and electron beam lithography. Characterization of microheterogeneous surfaces uses Low Voltage Scanning Electron Microscopy (LVSEM), AFM- and various light microscopic techniques. The physicochemical processes under investigation include wetting, dewetting and ordering phenomena in particular crystallization processes in ultrathin films.
Self-organized amino terminated polyethyleneoxide lamella additionally patterned by electron beam lithography
Microdroplet array prepared by dip-coating of liquid phase on microheterogenized surface
Future prospects and goals
Beside the engineering of solid surfaces future work will also include the preparation, characterization and use of microstructured liquid/liquid interfaces and the self-assembly of lipids and photopolymerizable interfacial compounds based on diacetylene units. The polymeric membranes obtained by topochemical photopolymerizations of the diacetylenes show intense fluorescence which is related to the conformation of the polyconjugated polymer chains. The onset of fluorescence can be triggered by external stresses and is therefore an interesting opportunity to sensor local stresses at membranes and soft interfaces.
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Selected publications
Salzer, R., Zimmerer, C., Kitsche, M., Steiner, G. & Braun, H.-G.: Molecular imaging of microstructured polymer surfaces. Progr. Colloid Polym. Sci. 132, 7–15 (2006)
Meyer, E. & Braun, H. G.: Film formation of crystallizable polymers on microheterogeneous surfaces. JOURNAL OF PHYSICS-CONDENSED MATTER 17, S623–S635 (2005)
Wang, M. T., Braun, H. G., Kratzmüller, T. & Meyer, E.: Patterning polymers by microfluid-contact printing. ADVANCED MATERIALS 13, 1312–1317 (2001)
Meyer, E. & Braun, H. G.: Controlled dewetting processes on microstructured surfaces a new procedure for thin film microstructuring. MACROMOLECULAR MATERIALS AND ENGINEERING 276, 44–50 (2000).
Kratzmüller, T., Appelhans, D. & Braun, H. G.: Ultrathin microstructured polypeptide layers by surface-initiated polymerization on microprinted surfaces. ADVANCED MATERIALS 11, 555–+ (1999)