Non-equilibrium flow at gradient surfaces: Fluid kinetics of droplets and particle motion

• Applicants: Professor Dr. Peter Müller-Buschbaum; Professor Dr. Manfred Stamm; Professor Dr. Fathollah Varnik
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2004 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5425061

Flow in nanoscale geometries is of importance in many areas as for example in chip production, printing techniques and bio-medical sensing devices. The experimental investigation focuses on non-equilibrium flow in nanoscale geometries to be generated by topographic or chemical surface structuring. The fluidics will be influenced by confinement given by nano-channels, which are produced via nano-scale phase separation of copolymers, by different surface functionalities, which may be similarly spatially structured, or by surface gradients, which are obtained with mixed polymer brushes. Flow will be investigated with solutions containing polymers and different liquids thus providing a tunable model system for the investigation of non-equilibrium flow. By variation of polymer concentration the viscosity is adjusted, and by the presence of a source or drain for the solution the non-equilibrium flow is controlled. Channeled substrates provide a confinement of the flowing solution into the restricted space of the channels and flow is investigated by microscopic and scattering techniques as a function of control parameters such as channel width, channel roughness or channel morphology. The surface can be modified by chemical reaction to provide specific functionality. For instance hydrophobic or hydrophilic behavior can be achieved, thus changing interaction between substrate and components of the solution. Chemically structured or gradient substrates provide a spatial variation of this interaction which with respect to nanofluidics could show a similar effect as channeled substrates. Thus both topographic and chemically structured functionalized model surfaces will be compared with respect to their influence on nanofluidics of polymer solutions and mixed liquids to provide a better understanding and possibly control of flow at nanoscopic level.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1164: Nano- and Microfluidics: Bridging the Gap between Molecular Motion and Continuum Flow
• Participating Person: Professor Dr.-Ing. Dierk Raabe