DFG Priority Program SPP 1164
Nano- & Microfluidics:
Bridging the Gap between
Molecular Motion and Continuum Flow
Hydrodynamic interactions along and between polymers in simple flow fields
| Project Leader: | Prof. Dr. Walter Zimmermann Universität Bayreuth Lehrstuhl für Theoretische Physik I Bayreuth |
Summary
A number of spectacular and fascinating flow phenomena in polymer
solutions are known for a long time but their physical basis is still
poorly understood. Due to their technological importance and a wide
range of applications, previous studies were undertaken mostly by
chemical and mechanical engineers with emphasis of practical aspects. A
thorough understanding of the polymer dynamics at the nano- and
microscale for both, macroscopic polymer flows and the recently studied
nano- and microscaled channel flows is challenging, but a
necessity also for substantial improvements in applications.
Flow induced deformations of polymers, which take place at the nano- and micrometer scale can be observed only recently. The second major effect of the complex polymer-flow interaction is the opposite, namely that the polymer motion causes flow perturbations which are yet experimentally unobserved but which have dramatic consequences for microscopic and macroscopic polymer flows.
Any moving part of a polymer perturbs the fluid motion and this in turn perturbs the motion of other parts of the polymer. This so-called hydrodynamic interaction (HI) depends on the polymer conformation, it is nonlinear and decreases only slowly with the distance between the interacting parts. It affects the Brownian motion of single polymers and also causes an interaction of non-overlapping neutral polymers. Despite these important facts the Hl is often neglected in mesoscopic models. Depending on the type of polymer motion, the size of the polymer and its internal structure, on the environment of the polymer and the surface structure of channel boundaries, the Hl may be more or less important, but this is not known a priory. Therefore, the aim of this project is to determine the Hl effects for a variety of “model experiments” on polymers, vesicles and actin networks in flows.
The projects includes the dynamics of tethered polymers in periodically and randomly time dependent plug flow and shear flow (Batchelor limit), as well as the dynamics of free polymers in shear flows, the investigation of semiflexible polymer brushes in narrow channels, the rotational viscosity of colloidal particles with a polymer coat the crossstreamline migration of deformable objects in plane Poiseuille flow, possibly fluctuations of the solvent and the suspended particles that are modified in shear flow, i.e. by inertia effects.
Some of these theoretical ideas have already inspired experiments and most of the subjects addressed in this project are planned in close collaboration with experimental groups.
Flow induced deformations of polymers, which take place at the nano- and micrometer scale can be observed only recently. The second major effect of the complex polymer-flow interaction is the opposite, namely that the polymer motion causes flow perturbations which are yet experimentally unobserved but which have dramatic consequences for microscopic and macroscopic polymer flows.
Any moving part of a polymer perturbs the fluid motion and this in turn perturbs the motion of other parts of the polymer. This so-called hydrodynamic interaction (HI) depends on the polymer conformation, it is nonlinear and decreases only slowly with the distance between the interacting parts. It affects the Brownian motion of single polymers and also causes an interaction of non-overlapping neutral polymers. Despite these important facts the Hl is often neglected in mesoscopic models. Depending on the type of polymer motion, the size of the polymer and its internal structure, on the environment of the polymer and the surface structure of channel boundaries, the Hl may be more or less important, but this is not known a priory. Therefore, the aim of this project is to determine the Hl effects for a variety of “model experiments” on polymers, vesicles and actin networks in flows.
The projects includes the dynamics of tethered polymers in periodically and randomly time dependent plug flow and shear flow (Batchelor limit), as well as the dynamics of free polymers in shear flows, the investigation of semiflexible polymer brushes in narrow channels, the rotational viscosity of colloidal particles with a polymer coat the crossstreamline migration of deformable objects in plane Poiseuille flow, possibly fluctuations of the solvent and the suspended particles that are modified in shear flow, i.e. by inertia effects.
Some of these theoretical ideas have already inspired experiments and most of the subjects addressed in this project are planned in close collaboration with experimental groups.