%0 Book Section %1 statphys23_0637 %A Viallat, A. %A Abkarian, M. %A Vezy, C. %B Abstract Book of the XXIII IUPAP International Conference on Statistical Physics %C Genova, Italy %D 2007 %E Pietronero, Luciano %E Loreto, Vittorio %E Zapperi, Stefano %K blood cells flow red shear statphys23 topic-7 vesicles %T Deformation and dynamics of viscoelastic shells under flow. Giant vesicles and red blood cells %U http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=637 %X Giant lipid vesicles and red blood cells belong to a class of deformable fluid objects of several microns of tens of microns and which present a surface composed of a conservative area membrane. In this sense, these objects differ from droplets ou bubbles, whose area can vary when the droplet or the bubble is deformed. We are interested to the behavior of these objects when their mechanical properties are varied : fluid or elastic membrane, viscous or viscoelastic inner medium. We present an experimental and theoretical description of the tumbling, tanktreading and swinging motion of viscous vesicles and elastic red blood cells in a shear flow. In particular, we reveal that under moderate shear stress ($\eta\gamma\approx0.1$ Pa) red blood cells present an oscillation of their inclination (swinging) superimposed to the long-observed steady tanktreading (TT) motion. A model based on a fluid ellipsoid surrounded by a visco-elastic membrane initially unstrained (shape memory) predicts all observed features of the motion: an increase of both swinging amplitude and period (1/2 the TT period) upon decreasing $\eta\gamma$, a $\eta\gamma$-triggered transition towards a narrow $\eta\gamma$-range intermittent regime of successive swinging and tumbling, and a pure tumbling at low $\eta\gamma$-values. We finally explore the flow at the surface of strongly adhering giant lipid vesicles submitted to an external shear flow. The surface flow is divided into two symmetric quadrants and present two stagnation points (SP) on each side of the vesicle meridian plane. The position of these stagnation points highly depends on the adhesion strength, characterized by the ratio of the contact zone diameter to the vesicle diameter. Contrary to the case of non adhesive vesicles, streamlines do not lie in the shear plane. By avoiding the motionless contact zone, streamlines result in three-dimensional paths, strongly asymmetric away from the SP. Additional shearing dissipation may occur on the membrane surface as we observed that the mean rotational velocity of the membrane increases towards the vesicle SP, and is mainly determined by the adhesion induced vesicle shape.

@incollection{statphys23_0637, abstract = {Giant lipid vesicles and red blood cells belong to a class of deformable fluid objects of several microns of tens of microns and which present a surface composed of a conservative area membrane. In this sense, these objects differ from droplets ou bubbles, whose area can vary when the droplet or the bubble is deformed. We are interested to the behavior of these objects when their mechanical properties are varied : fluid or elastic membrane, viscous or viscoelastic inner medium. We present an experimental and theoretical description of the tumbling, tanktreading and swinging motion of viscous vesicles and elastic red blood cells in a shear flow. In particular, we reveal that under moderate shear stress ($\eta\dot{\gamma}\approx0.1$ Pa) red blood cells present an oscillation of their inclination (swinging) superimposed to the long-observed steady tanktreading (TT) motion. A model based on a fluid ellipsoid surrounded by a visco-elastic membrane initially unstrained (shape memory) predicts all observed features of the motion: an increase of both swinging amplitude and period (1/2 the TT period) upon decreasing $\eta\dot{\gamma}$, a $\eta\dot{\gamma}$-triggered transition towards a narrow $\eta\dot{\gamma}$-range intermittent regime of successive swinging and tumbling, and a pure tumbling at low $\eta\dot{\gamma}$-values. We finally explore the flow at the surface of strongly adhering giant lipid vesicles submitted to an external shear flow. The surface flow is divided into two symmetric quadrants and present two stagnation points (SP) on each side of the vesicle meridian plane. The position of these stagnation points highly depends on the adhesion strength, characterized by the ratio of the contact zone diameter to the vesicle diameter. Contrary to the case of non adhesive vesicles, streamlines do not lie in the shear plane. By avoiding the motionless contact zone, streamlines result in three-dimensional paths, strongly asymmetric away from the SP. Additional shearing dissipation may occur on the membrane surface as we observed that the mean rotational velocity of the membrane increases towards the vesicle SP, and is mainly determined by the adhesion induced vesicle shape.}, added-at = {2007-06-20T10:16:09.000+0200}, address = {Genova, Italy}, author = {Viallat, A. and Abkarian, M. and Vezy, C.}, biburl = {https://www.bibsonomy.org/bibtex/273b581fb4511f0c28552897e22363f0f/statphys23}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Pietronero, Luciano and Loreto, Vittorio and Zapperi, Stefano}, interhash = {cb1f248c6cbf6e8dfd55651c5f799857}, intrahash = {73b581fb4511f0c28552897e22363f0f}, keywords = {blood cells flow red shear statphys23 topic-7 vesicles}, month = {9-13 July}, timestamp = {2007-06-20T10:16:25.000+0200}, title = {Deformation and dynamics of viscoelastic shells under flow. Giant vesicles and red blood cells}, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=637}, year = 2007 }