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Dynamics of Confined Complex Suspensions (DYCOCOS)
Start date: Sep 1, 2014, End date: Aug 31, 2016 PROJECT  FINISHED 

"Soft condensed materials are ubiquitous in nature: from polymer melts to a human cell. These systems are characterized by complex order on mesoscale, a length scale a lot larger than the individual building blocks (e.g. atoms or molecules) but smaller than can be seen by naked eye. Examples of complex soft materials are provided by colloidal systems - 0.1-10 micron particles suspended in a homogeneous fluid or liquid crystals (LCs) which can have order (orientational/translation) but can flow like fluids. In anisotropic complex fluids the morphology of the phase is inherently connected to the dynamics (e.g. flow). Confinement effects also play a major role in technologically relevant configurations e.g. sedimentation or microfluidics.The candidate proposes computational research of the sedimentation dynamics of confined colloidal solutions as well as the dynamics and optics of liquid crystals in microfluidics (""optofluidics""). Confining walls hinder the sedimentation dynamics, leading to decreased draining. Very recent experiments showed an increased sedimentation velocity of colloids when confined in cylindrical capillaries (Heitkam et al. PRL (2013)). This serves as a natural starting point for the research. Subsequently, the studies will be expanded to include various confining geometries and interactions (particle-particle and particle-wall). Due to the coupling between the LC orientation and imposed flow, confining LCs in microfluidic channels allows optical manipulation (""optofluidics""). Proposed research of LC optofluidics will govern LCs with orientational (nematic) and combined orientational/translational (cholesteric) order.The results can be expected to have significant technological relevance, although the primary aim is to provide fundamental physics insights of the coupling between flow and order in confined complex fluids. This will be achieved by employing state-of-the-art simulations (lattice Boltzmann) in close contact with experiments."
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