Greiner, Alexander

• Experiments, modelling and computational simulations to characterize the porous and viscous behaviour of human brain tissue

  (Third Party Funds Single)

  Project leader: Silvia Budday, Paul Steinmann
  Term: 1. July 2021 - 30. April 2024
  Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
  Abstract

  Computational modelling in biomechanics can provide important insights into the underlying mechanisms of cerebral pathologies that go far beyond the possibilities of traditional methods. The improvement of current prevention and treatment strategies via numerical simulation can only be achieved with a realistic biomechanical model for brain tissue. Understanding and characterizing its short- and long-term biomechanical response, and linking it to its underlying microstructure is essential to develop reliable models. We aim to characterize the mechanical response of brain tissue via the development of a biphasic constitutive model based on a comprehensive set of experimental data. To achieve this goal, the work program is divided into four specific aims: (1) We will devise new experimental set-ups to adequately characterize the visco-porous nature of brain tissue under arbitrary loading conditions. There are very few published studies characterizing the porous effects in brain tissue, all restricted to a single loading mode. Yet, we need to to fit multiple loading conditions simultaneously for the identified model parameters to produce accurate computational results. (2) We will elucidate the relation between the macroscopic mechanical response and the tissue microstructure through microstructural investigations of the tested samples, and, potentially, identify structural model parameters. These investigations are key to confirming our assumptions that porous and viscous phenomena observed in experiments are intrinsically linked to the tissue components, and the interconnectivity of cells. (3) We will develop a poro-viscoelastic model to capture, at the continuum level, the individual effects of the fluid and solid components, and their interaction. The experimental findings in (1) and the structural parameters identified in (2) will enable us to replace phenomenological constitutive equations, previously used to describebrain tissue behaviour, with comprehensive microstructurally motivated material laws. A robust finite element framework will allow for the successful implementation of the proposed model. (4) We will accurately calibrate the model parameters through an inverse material parameter identification scheme and evaluate their physical meaning considering the observed porous and viscous phenomena. The outcome of the project will be a better understanding of the role porous and viscous effects have in the response of brain tissue to mechanical loading. We will have linked the miscrostructure of the tissue to its macroscopic behaviour via experimental and computational investigations. With the resulting calibrated model, we will further explore how structure and mechanical response are linked, as well as demonstrate the potential for application of the proposed model in clinically-relevant problems.

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• Experimente, Modellierung und Computersimulationen zur Charakterisierung des porösen und viskosen Verhaltens von menschlichen Gehirngewebe

  (Third Party Funds Single)

  Project leader: Paul Steinmann
  Term: 1. July 2021 - 30. April 2024
  Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
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• BRAIn mechaNIcs ACross Scales: Linking microstructure, mechanics and pathology

  (Third Party Funds Single)

  Project leader: Silvia Budday
  Term: 1. October 2019 - 30. September 2025
  Acronym: BRAINIACS
  Funding source: DFG-Einzelförderung / Emmy-Noether-Programm (EIN-ENP)
  URL: https://www.brainiacs.forschung.fau.de/
  Abstract

  The current research project aims to develop microstructurallymotivated mechanical models for brain tissue that facilitate early diagnosticsof neurodevelopmental or neurodegenerative diseases and enable the developmentof novel treatment strategies. In a first step, we will experimentallycharacterize the behavior of brain tissue across scales by using versatiletesting techniques on the same sample. Through an accompanying microstructuralanalysis of both cellular and extra-cellular components, we will evaluate thecomplex interplay of brain structure, mechanics and function. We will alsoexperimentally investigate dynamic changes in tissue properties duringdevelopment and disease, due to changes in the mechanical environment of cells (mechanosensing),or external loading. Based on the simultaneous analysis of experimental andmicrostructural data, we will develop microstructurally motivated constitutive lawsfor the regionally varying mechanical behavior of brain tissue. In addition, wewill develop evolution laws that predict remodeling processes duringdevelopment, homeostasis, and disease. Through the implementation within afinite element framework, we will simulate the behavior of brain tissue underphysiological and pathological conditions. We will predict how known biologicalprocesses on the cellular scale, such as changes in the tissue’smicrostructure, translate into morphological changes on the macroscopic scale,which are easily detectable through modern imaging techniques. We will analyzeprogression of disease or mechanically-induced loss of brain function. The novelexperimental procedures on the borderline of mechanics and biology, togetherwith comprehensive theoretical and computational models, will form thecornerstone for predictive simulations that improve early diagnostics of pathologicalconditions, advance medical treatment strategies, and reduce the necessity ofanimal and human tissue experimentation. The established methodology will furtheropen new pathways in the biofabrication of artificial organs.

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• Multiscale modeling of nervous tissue: comprehensively linking microstructure, pathology, and mechanics

  (FAU Funds)

  Project leader: Silvia Budday
  Term: 1. July 2018 - 30. June 2019
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Laboratory Training Biomechanics

since 2023