Berlin 2008 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 11: DRG-DPG SYMPOSIUM Rheology III

CPP 11.1: Talk

Tuesday, February 26, 2008, 10:00–10:15, C 264

Blood-Rheology on single drops before, during and after coagulation — •Wolfgang Pechhold, Theresia Groß, and Hubert Dammann — Institute for dynamic Materials Testing (IdM) at the University Ulm

Blood is a complex fluid in many respects. It contains about 45 p.c. of hematocrit (RBC, WBC and platelets) in low viscous plasma (1,8 mPa s), with dissolved proteins and clotting factors, including fibrinogen (2%). We report on its viscoelastic characterization (η = η'-iη") in the frequency range 1 Hz to 3 kHz using the dynamic squeeze flow of the Piezo Axial Vibrator (PAV) which needs only a droplet (10-50μl) of blood or plasma: in the anticoagulated state we varied the hematocrit from 0 to 92 p.c. and found an exponential increase of viscosity above 40 p.c. In full blood we measured η in the course of time before and during coagulation and found a strong gap dependence in the clotted state in both, intrinsic and extrinsic, clotting. Adding Heparin to the blood droplet, the clotting time becomes prolonged and exceeds 100 min for 1800 I.E. per 5 l. In platelet-free plasma no intrinsic coagulation takes place, and in high platelet-concentration (1,2 E6/mm3) we did not find any change in clotting time up to 3600 I.E. per 5 l Heparin added. For the used blood in all measurements of the coagulated state, i.e. after fibrin forming, the viscous part clearly dominated at all frequencies.