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Logo: Institute of Continuum Mechanics/Leibniz Universität Hannover
Logo Leibniz Universität Hannover
Logo: Institute of Continuum Mechanics/Leibniz Universität Hannover
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Biomechanics

Computational modeling of in-stent restenosis

 

Supervisor:

M. Marino

Funded by:

Masterplan SmartBiotecs, MWK (Lower Saxony, Germany)

Brief description:

This project aims to develop a computational tool for the modeling of the long-term behaviour of stent deployment, with a special focus on both current and prospective approaches. A multiscale description of arterial constitutive behaviour will be employed, including possible damage due to the stenting procedure. Moreover, the chemo-biological mechanisms underlying the growth and remodelling due to wound healing in tissues will be introduced. Therefore, a multiphysics computational framework will be developed and applied for the analysis of both metal and drug-eluting stents. The project will allow to identify the dominant mechanisms driving in-stent restenosis, deciphering the role of the different molecular species in the pathological remodeling of arteries. The final target is to optimise the clinical outcome of current approaches and propose targeted therapeutic approaches.

 

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Patient-Specific FSI Analysis of the Blood Flow in the Thoracic Aorta

Bild zum Projekt Patient-Specific FSI Analysis of the Blood Flow in the Thoracic Aorta

Supervisor:

P. Wriggers, B. Avci

Researcher:

B. Avci

Brief description:

The complexity of numerical modeling and simulation of blood flow in patient-specific thoracic aorta geometries leads to a number of major computational challenging issues. For instance, for an adequate simulation of the flow and pressure field, the incompressible Navier-Stokes equations have to be solved with the assumption that the relatively thin blood vessels suffer large displacements and undergo large elastic or visco-elastic deformations caused by the pulsatile blood flow. Subsequently, inaccurate predictions would be obtained for the hemodynamic quantities with the very simplifying rigid-wall assumption (CFD modeling). Moreover, when applying only the CFD modeling approach the essential phenomena of pressure wave propagation in cardiovascular systems are disregarded, however these phenomena are of major relevance for clinical practice. Accordingly, strongly coupled FSI schemes are inevitable for comprehensive blood flow simulations in arterial systems, and as blood and vascular walls have comparable densities, monolithic or at least partitioned strongly coupled FSI schemes are required for solving the multi-physics problem with its inherent significant added-mass effects.

 

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Interface effects and ingrowth behaviour of magnesium sponges as bioresorbable bone-replacement material

Bild zum Projekt Interface effects and ingrowth behaviour of magnesium sponges as bioresorbable bone-replacement material

Supervisor:

P. Wriggers

Researcher:

A. Krüger

Funded by:

DFG

Brief description:

Within this project sponge-like structures made of magnesium alloys are being developed and investigated as bone-replacement material. The advantage of magnesium is that it naturally occurs in the body and that it degrades gradually. The developed implants will be investigated regarding to the occurring interface effects in cooperation with the Institute of Material Science of the Leibniz University Hanover and the Surgical and Gynaecological Small Animal Clinic of the Ludwig-Maximilians-University Munich. Finite element methods are extensively used for the development and investigation of the sponges. Based on in vitro and in vivo results the simulation model will be build up and validated. The simulation model includes the interface effects, like degradation of the implant and ingrowth behaviour of the bone into the sponge structure. The change of the mechanical properties during the degradation has to be considered in the simulations.

 

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Simulation of atherosclerotic plaque impact on the red blood cells dynamics in arteries

Bild zum Projekt Simulation of  atherosclerotic plaque impact  on the red blood cells dynamics  in arteries

Supervisor:

P. Wriggers

Researcher:

M.R.Hojjati

Funded by:

DAAD

Brief description:

Atherosclerosis, a coronary disease, is one of the main cause of mortality in the many countries. Atherosclerosis emerges as a results of hardening and narrowing of the blood vessels , caused by the gradual accumulation of deposits on the inside of arteries walls. This finally leads to atherosclerotic plaque. In this work, The impact of atherosclerotic plaque on red blood cells (RBC) dynamics in the blood vessels is studied. A fluid-solid interaction (FSI) analysis is developed. For the fluid phase, a mesh-less Lagrangian method is adopted which is called smoothed particle hydrodynamics (SPH). RBCs are considered to be the solid phase and are assumed to behave like deformable solid floated in the blood. A strong two way coupling is developed in the context of immersed boundary method (IBM) to capture the accurate fluid-solid interaction.

 

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Numerical Simulation and Experimental Validation of Biofilm Growth

Bild zum Projekt Numerical Simulation and Experimental Validation of 
Biofilm Growth

Supervisor:

P. Wriggers , M. Stiesch

Researcher:

M. Soleimani

Brief description:

Biofilms are bacterial colonies growing on solid-fluid interfaces, wherever enough dissolved nutrients are available. Their formation is a complex process in the sense that several Physical phenomena (Reaction-Diffusion-Advection, Sedimentation, Erosion, Fluid-Solid-Interaction) are coupled and consequently different time-scales are involved. In this project, the focus is on the biofilm formation in a flow chamber which resembles the mouth cavity in the vicinity of dental implants. The goal is to develop a computational tool capable of simulating the biofilm growth. Numerical solution of the Navier–Stokes equation in domains with complex boundaries that dynamically change as a result of biological diffusion-reaction, detachment and sedimentation in biofilm growth presents a very serious challenge to grid-based methods. In this project, a fully Lagrangian particle approach(mesh-less method) based on smoothed particle hydrodynamics (SPH) is developed.

 

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Gekoppelte Simulation von Aerosolströmungen in asthmatischen Bronchien

Bild zum Projekt Gekoppelte Simulation von Aerosolströmungen in asthmatischen Bronchien

Supervisor:

P. Wriggers, B. Avci

Researcher:

J. Stasch, J.-P. Fürstenau

Funded by:

Leibniz Universität Hannover, Wege in die Forschung

Brief description:

Das Ziel dieses Projektvorhabens ist es, auf Basis eines gekoppelten 3D Mehrfeldmodells die partikelbeladene Luftströmung in gesunden sowie in asthmatisch verengten Bronchien anhand von numerischen Simulationen zu studieren.

 

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SFB 599 TP R6 – Degradable Osteosynthese

Bild zum Projekt SFB 599 TP R6 – Degradable Osteosynthese-Systeme

Supervisor:

P. Wriggers

Researcher:

S. Besdo

Funded by:

DFG im Rahmen des SFB 599

Brief description:

Within the framework of SFB 599 osteosynthesis systems for fracture stabilization out of magnesium alloys are being developed. The advantage of magnesium is that the body needs it for its metabolism and it degrades over time. Due to the mechanical properties and the degradation of magnesium alloys, it is necessary to adjust the implant design. First, the primary stability of implant-bone composite is investigated using finite element analysis, before the implants are tested on animals. In a second step, the degradation has to be integrated into the simulation. Therefore, different simulation methods have been developed and should be adapted to results from in vitro experiments. Furthermore, the magnesium degradation will be considered in the simulation of bone healing.

 

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SFB 599 TP D1 – Functionalized middle ear prostheses

Bild zum Projekt SFB 599 TP D1 – Funktionalisierte Mittelohrprothesen

Supervisor:

P. Wriggers

Researcher:

S. Besdo, D. Doniga-Crivat

Funded by:

DFG im Rahmen des SFB 599

Brief description:

The participating institutions in the sub-project D1 of the SFB 599 (Institute of Inorganic Chemistry, LUH, Helmholtz Centre for Infection Research, Ear, Nose and Throat Clinic, Hannover Medical School, IKM) have the aim to develop an optimized middle ear prosthesis. This is done through the use of newly developed biomaterials on the one hand and by using simulation techniques to optimize the design on the other hand. During the last funding period, the focus of the simulation was on the healthy ossicular chain. In the third period the contact between the implant and the tympanic membrane should be simulated. Polymer cushions will be used to create a tissue-friendly interface that enables a uniform loading of the eardrum.

 

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Improvement of cardiovascular Implants and a FE-Framework for Degradation of Mg-Alloys

Bild zum Projekt Weiterentwicklung von kardiovaskulären Implantaten und finite Element Modellierung der Degradation von Mg-Legierungen

Supervisor:

P. Wriggers, J. Lamon, S. Besdo

Researcher:

M. Weidling

Funded by:

DFG within IRTG 1627

Brief description:

A surgical option is to replace damaged myocardial tissue, e. g. after a heart attack, with tissue transplants. Problematic is the minor initial strength of these biological grafts to resist loads of the high pressure system. Therefore, scaffolds are developed to mechanically support these grafts. Until now, developed scaffolds do not achieve the required durability. With use of the finite element method, simulations are performed where the scaffolds are deformed according to the heart movement. This allows identifying highly strained regions within the implant that need design changes. Another approach to reduce stresses is preforming scaffolds according to the heart curvature preoperatively. Further, new scaffold designs are developed and tested.  Scaffolds are made from magnesium alloys, which can be resorbed by the body. This degradation affects the mechanical behavior of the implants under load. There are FE simulations developed in which the magnesium degradation is considered.

 

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Investigation of the behavior of the crystalline lens accommodation by introducing femtosecond laser-induced (fs-laser) cut surfaces

Bild zum Projekt Untersuchung des Akkommodationsverhaltens der Augenlinse nach Einbringung Femtosekun-den-Laser-induzierter (fs-Laser) Schnittflächen

Supervisor:

S. Besdo

Funded by:

DFG im Normalverfahren

Brief description:

This project is conducted in cooperation with the Laser Zentrum Hannover eV. With age, the ability of the human eye lens to adjust from the distant view of the near vision increases. There is still no satisfactory method of treatment for the so called pres-byopie. However, it was shown that it is possible to influence the flexibility of the lens by introducing micro-cuts with a femtosecond laser (fs-Lentotomie). The aim of this project is to develop a method which makes it possible to predict the changes of accommodation behavior of ophthalmic lenses after cutting using finite element analyses.

 

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Design and Control of Additive Manufacturing Processes for Medical Silicone

 

Researcher:

M.Sc. Philipp Hartmann

 

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High Performance Computing of Stereolithography Processes

 

Researcher:

M.Sc. Sandeep Kumar

 

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Improved Frictional Models for Pile Installations

 

Researcher:

M.Sc. Ajay Harish

 

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A 3D CAD/CAE integration using isogeometric symmetric Galerkin boundary element method