"Experimental Analysis of Artificial Cerebral Blood Vessels"
Experimental Analysis of Artificial Cerebral Blood Vessels
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The goal of this thesis is to validate a material for manufacturing of artificial cerebral blood vessels that can be used in a neurosurgical aneurysm clipping simulator. This validation consists of the four main points: fabrication of artificial simplified blood vessels, development of a testing-setup, experimental measurement of the artificial blood vessels and comparison with a simulation.
The artificial blood vessels were fabricated by silicone (Dragon Skin 10 (Smooth-On, Macungie, USA))) casting. The moulds were fabricated by material extrusion Fused Filament Fabrication (FFF) and material jetting (PolyJet). To test those silicone specimen, an artificial ?heart? was built. It consists of a piston pump that is powered by a stepper motor. To force the flow in one direction two check valves were designed and printed. A requirement for the pump was to be able to realize different pressure profiles. To control the pressure the setup was equipped with a pressure sensor that was hooked up to a microcontroller that moves the motor to fit the required pressure at the time. The Strain was measured with the digital image correlation system ARAMIS by GOM (Braunschweig, Germany).
To compare the measured surface strains to a simulation, a material model was calculated to base the simulation on. For this purpose tensile, compression and biaxial tests were performed. The data was then fitted to a hyperelastic material model in MCalibration (PolymerFEM, LLC, Massachusetts, USA) and the resulting parameters are used in Abaqus (Simulia, Dassault Systemes, Velizy-Villacoubay, France) to perform a simulation with the pressure values acquired from the experiment. Finally the results of the simulation and the experiment were compared.
The measurements of the manufactured artificial blood vessels show a very good agreement with the values obtained with the simulation based on the created material model. Thus, the behaviour of Dragon Skin 10 can be reproduced well with the help of the created material model. In the future, it could also be used to analyse more complex geometries that are unsuitable for optical measurement of the surface strain. The material is therefore suitable for producing artificial blood vessels for the aneurysm clipping simulator and for reproducing the behaviour when subjected to a pressure curve that mirrors the behaviour of cerebral blood pressure.