We plan to study the deformation of single vesicles and red blood cells in hydrodynamic flow fields around them and their mutual interacting with the flow field. The coupling of the shear flow to the deformation and motion of individual soft object gives rise to complex dynamic phenomena such as a rotation of the membrane surface around its inner volume (tank treading), oscillatory (“swinging”) and unsteady (tumbling). In this experimental study we want to characterize these deformations and regimes of motion especially with respect to the viscoe-lastic material properties of soft objects in different shear flow fields. In order to create such flow fields, we intend to design microfluidic channels of varying geometry by soft lithography. The viscoelastic properties of vesicles should be altered by driving the lipid membrane through its temperature-induced fluid-gel transition or to use a binary or ternary mixture of cholesterol and lipids. The latter ones are also known to form domains (“rafts”) of either mi-croscopic or submicroscopic size. In accordance, the cholesterol content of red blood cells is planned to be varied as it is known to be of eminent biological and medical relevance. Furthermore, the deformability of RBCs changes with aging of cells or in diseases such as malaria, hypercholesterolemia and diabetes mellitus .
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