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Session: Poster session I
Session starts: Thursday 24 January, 15:00

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Thomas van Kempen (Eindhoven University of Technology)
Gerrit Peters (Eindhoven University of Technology)
Frans van de Vosse (Eindhoven University of Technology)

Abstract:
Blood clot formation serves to stop blood loss in case of a vascular injury but can also occur intravascularly, for instance after rupturing of an atherosclerotic plaque which may lead to myocardial infarction. The blood clot forms as a platelet plug and is subsequently stabilized by a network of fibrin fibers that forms within the clot. Fibrin increases the mechanical rigidity of the clot and is therefore of major importance for the mechanical properties of the clot [1]. The mechanical properties of the fibrin network play a role in many diseases but are nevertheless poorly understood. Therefore a constitutive model is developed to study the mechanical properties of the fibrin network based on structural quantities such as the size of the fibers and their stiffness. The fibrin network is modelled as a viscoelastic solid using the Kelvin-Voigt model, often represented as an elastic spring parallel to a viscous dashpot. By relating the shear modulus and viscosity of the model to the temporal fibrin concentration, the network formation is modelled as a transition from a viscous fluid to a viscoelastic solid. Model output is compared with rheometer experiments in which the network formation is followed in time by imposing an oscillatory shear deformation. Networks are formed with various initial fibrin concentrations under a range of frequencies. The model is able to describe the viscoelastic properties of the developing fibrin network as measured in the experiments. Three free parameters are used to fit the model to experimental results. The kinetic rate constant, that governs the kinetics of the network formation, does not very with initial concentration or frequency. The mass-length ratio of the fibers increases with concentration indicating that the fibers become thicker if more fibrin is initially available. The friction coefficient, that represents viscous drag within the fibers, decreases with frequency. Using the mass-length ratio of the fibers, the model is used to estimate the length and diameter of the fibers which gives values within the expected range found experimentally [2]. The results show that the fibrin network behaves as a viscoelastic solid, justifying the choice of the Kelvin-Voigt model. It is concluded that the model is able to describe the viscoelastic properties of the developing fibrin network.