h1

%0 Thesis
%A Hirschwald, Lukas Tobias
%T Hemodynamics in blood-contacting devices with triply periodic minimal surfaces for extracorporeal blood therapies
%V 50
%I Rheinisch-Westfälische Technische Hochschule Aachen
%V Dissertation
%C Aachen
%M RWTH-2025-01571
%B Aachener Verfahrenstechnik series - AVT.CVT - Chemical process engineering
%P 1 Online-Ressource : Illustrationen
%D 2025
%Z Veröffentlicht auf dem Publikationsserver der RWTH Aachen University
%Z Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2025
%X Extracorporeal organ support devices are life-saving in cases of lung or kidney failure. They bridge the time until the organ heals or is transplanted, which can take weeks or months. These support devices replace the organ's function by exchanging breathing gases or unwanted species over hollow fiber membranes. While short-term support is generally considered safe, long-term application often leads to severe complications. Until now, research has focused on improving biocompatibility by modifying the membrane's surface to reduce immune reactions that trigger blood clotting and eventually cause the device to malfunction. However, unphysiological flow conditions also trigger blood clotting. Additionally, commercial support devices suffer from an uneven flow distribution that leads to a broad residence time distribution (RTD) and unbalanced mass transfer driving forces. In order to exploit the device's full capacity, uniform residence times and homogeneous driving forces are essential. Recently, triply periodic minimal surfaces (TPMS) have emerged as novel topologies to substitute hollow fiber membranes in blood-contacting devices. They offer more design freedom and increase mass transfer at lesser artificial surfaces by introducing secondary flows that reduce boundary layer effects. However, the influence of TPMS topologies on hemodynamics have hardly been investigated. In this thesis, I employed computational fluid dynamics simulations, human whole blood experiments, and simulative optimization to evaluate and optimize the hemodynamics in differently designed modules with isometric and anisometric TPMS topology compared to a conventional tubular architecture. The simulations, validated by RTD experiments, highlighted the advantageous topology of TPMS that notably enhanced the flow distribution. By post-experimental computed tomography scanning, the location and amount of formed blood clots were visualized and quantified. The blood clot locations largely matched regions of elevated shear rates predicted by the simulations, emphasizing the importance of physiological hemodynamics. Furthermore, the blood clot amounts revealed significantly less clotting in the anisometric TPMS module compared to the tubular module. Further improvement of the RTD was simulatively achieved through Bayesian optimization by subdividing the module's fluid volume into independent domains and varying the domains' permeability. With this procedure, the RTD can be optimally tailored within a given external shape, e.g., a lung lobe, to enable the design of patient-individualized devices. Overall, my work demonstrated that anisometric TPMS topologies with anisotropic properties have the potential to significantly improve hemodynamics in blood-contacting devices. Deploying anisometric TPMS as substitutes for hollow fiber membranes could be a major step forward in the long-term application and even implantability of lung or kidney replacement systems.
%F PUB:(DE-HGF)11 ; PUB:(DE-HGF)3
%9 Dissertation / PhD ThesisBook
%R 10.18154/RWTH-2025-01571
%U https://publications.rwth-aachen.de/record/1004690