Christoph A. Weber
PhD student in the group of Prof. Erwin Frey, LMU Munich
2007 – 2008
Diploma Thesis in the group of Prof. Erwin Frey, LMU Munich
Topic of Diploma Thesis: “Modeling of Free Flow Isoelectric Focusing”
2003 – 2008
Diploma in Physics at the LMU Munich
Scholarship of the IDK-NBT (Elite Network of Bavaria)
1.) Active Fluids:
The collective motion of animal groups like flocks of birds, swarms of fishes or herds of wildebeests are fascinating spectacles in nature due to the emergence of dynamic patterns which entend on length scales much larger than the size of the individuals. Individuals driven by an intrinsic force belong to a broad class of systems called active fluids. The fluid-like character stems from the large amount of individuals while the activity could be of various origin. On the micrometer scale further representative of the class of active fluids are self-propelled bacteria and biofilaments driven by molecular motors. Interestingly, all active systems are non-equilibrium systems, show coherent motion accompanied by patterns on large length scales. From a theoretical point of view, two questions about active fluid systems are of central interest: What is the origin of pattern formation and how generic is the origin of the particular active systems considered?
A special active fluid is the high density motility assay, where actin filaments move across a 2d lawn of molecular motors. The molecular motors hydrolyse ATP to drive the actin filaments by the so called power stroke. At sufficient high densities beautiful patterns emerge extending from coherently moving clusters, swirls and density waves. The theoretical tools to account for the origin of pattern formation are kinetic equations on the one hand and numerical approaches on the other hand.
2.) Modeling of transport processes in microfluidic devices:
The miniaturization of chemical and physical devices comes along with new physical phenomena, mostly based on the increased significance of surface forces in comparision to body forces. Famous examples for such surface forces are electroosmosis, capillar forces or surface tension. To ensure the functionality of these devices, e.g. in mixing or separation, it is essential to understand the dominant physics involved. Then, even an improvement of the devices‘ results, e.g. the resolution of separation is feasible.
The projects concern the modeling of the electrophoretic separation methods, for example Free Flow Isoelectric Focusing. There, amphoteric molecules like proteins are exerted to a convective, continuous flow while being separated in two fields: a chemical pH-gradient and an electric field. The related resolution is excellent and predestines this technique for medical diagnostic and lab-on-chip due its continuity.
A further project is the modeling of a convective flow device to exert transient chemoattractant fields on cells attached to a surface. Here the central aim is to develope a theoretical framework to understand the impact of the parameters on the hydrodynamic equations as well as to explore the limits of the experimental device.
V. Schaller, C. A. Weber, E. Frey, A. Bausch:
"Polar Pattern Formation: Hydrodynamic coupling of driven filaments"
Soft Matter, Advance Online Publication (2011)
V. Schaller, C. A. Weber, C. Semmrich, E. Frey, A. R. Bausch:
"Polar patterns of driven filaments"
Nature 467, 73–77 (2010)