Experimental and theoretical investigations of the dynamics of collective phenomena in blood II: Towards a physically more realistic model

• Applicants: Professor Dr. Thomas Franke; Professor Dr. Fathollah Varnik
• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
• Term: from 2007 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 58652358

• Final Report Year: 2018

Final Report Abstract

Within this project, various aspects of the rheology and dynamics of dense suspensions of non-aggregating RBCs have been investigated via computer simulations and experiments. Important progress has been made regarding effective suspension viscosity, yield stress and shear-induced diffusion. The issue of collective dynamics has been also addressed and its relevance has been highlighted. Moreover, experiments have been performed to explore the lift forces for the important biomedical application of cell sorting. Yield stress has been rationalized by considering the energy stored in a deformed cell. The main idea here is that, in the limit of vanishing shear rate, red blood cells do not need to deform if the concentration is below a critical value, φc. Thus, the amount of deformation and the associated stress is a function of distance to φc. Using elastic properties of a single cell on the one hand and the packing-induced deformation on the other hand, a set of scaling relations is worked out and the dependence of yield stress on packing fraction is predicted. Moreover, it is also shown that yield stress obeys a generic critical jamming behavior. Moreover, a dissipation ansatz has been invoked to relate shear-induced diffusion to the suspension’s effective viscosity, resulting in D ∼ η 1/2 . This prediction has been shown to be in line with results obtained from extensive numerical simulations. Importantly, the theoretical arguments used to rationalize simulation results on RBC suspensions do not rely on the particular shape of RBCs. It would be interesting to explore these predictions for other types of athermal capsule suspensions both regarding rheological response and shear-induced diffusion. Another issue for further research concerns the length scale associated with jamming transition and its putative divergence.

Publications

• "Crossover from tumbling to tank-treading-like motion in dense simulated suspensions of red blood cells", Soft Matter 9, 9008 (2013)
  T. Krüger, M. Gross, D. Raabe, F. Varnik
  
• "Particle stress in suspensions of soft objects", Phil. Trans. R. Soc. A 369, 2414–2421 (2011)
  T. Krüger, F. Varnik, D. Raabe
  
• "Separation of blood cells using hydrodynamic lift", Appl. Phys. Lett. 100, 183701 (2012)
  T.M. Geislinger, B. Eggert, S. Braumnüller, L. Schmid, and T. Franke
  
• "Sorting of circulating tumor cells (MV3-melanoma) and red blood cells using non-inertial lift", Biomicrofluidics 7, 044120 (2013)
  T.M. Geislinger and T. Franke
  
• "Acoustic modulation of droplet siye in a T-junction", Appl. Phys. Lett. 104, 133501 (2014)
  L. Schmid and T. Franke
  
• "Fluctuations and diffusion in sheared athermal suspensions of deformable particles", Europhys. Letters 108 , 68006 (2014)
  M. Gross, T. Krüger, F. Varnik
  
• "Hydrodynamic lift of vesicles and red blood cells in flow — from Fåhræus & Lindqvist to microfluidic cell sorting", Advances in Colloid and Interface Science 208, 161 (2014)
  T.M. Geislinger and T. Franke
  
• "Rheology of dense suspensions of elastic capsules: normal stresses, yield stress, jamming and confinement effects", Soft Matter 10, 4360 (2014)
  M. Gross, T. Krüger, F. Varnik
  
• "Hydrodynamic and label-free sorting of circulating tumor cells from whole blood", Appl. Phys. Lett. 107, 203702 (2015)
  T.M. Geislinger, M.E.M. Stamp, A. Wixforth, and T. Franke