Article
Mechanics
Nasser Firouzi, Marco Amabili
Summary: The aim of this work is to develop a non-linear finite element formulation for two-dimensional growth of soft tissues, and several examples are provided to validate the proposed model.
EUROPEAN JOURNAL OF MECHANICS A-SOLIDS
(2024)
Article
Biophysics
Qizhi He, Devin W. Laurence, Chung-Hao Lee, Jiun-Shyan Chen
Summary: This study extends a local convexity data-driven framework to model the mechanical response of a porcine heart mitral valve posterior leaflet, showing that the predictivity of the proposed nonlinear solver is generally less sensitive to loading protocols but more sensitive to insufficient coverage of experimental data. The study demonstrates the importance of rich data coverage in data-driven and machine learning approaches for modeling complex biological materials.
JOURNAL OF BIOMECHANICS
(2021)
Article
Mechanics
Carlos Castillo-Mendez, Armando Ortiz
Summary: This study examines the impact of using different strain invariants in numerical modeling of soft tissues, proposes model adjustments accordingly, and validates them with experimental data. The main difference lies in the models' description of shear behaviors, with the proposed model predicting more diverse shear responses.
INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS
(2022)
Article
Mechanics
Arthesh Basak, Amirtham Rajagopal, Umesh Basappa, Mokarram Hossain
Summary: Biological tissues exhibit isotropic behavior at lower strain values, but show anisotropic behavior at higher strains as fibers straighten and bear load. This anisotropy can be mathematically modeled by considering the strains experienced by fibers. It is found that fibers have an oblique mean orientation around physiological loading directions, requiring a mathematical framework with tensors defined in a nonorthogonal basis to capture the direction-dependent response.
INTERNATIONAL JOURNAL OF APPLIED MECHANICS
(2021)
Article
Acoustics
Xiang Yu, Yibin Fu, Hui-Hui Dai
Summary: A refined dynamic finite-strain shell theory for incompressible hyperelastic materials is developed in this paper, with focus on wave propagation and bending effects. The theory is shown to be more accurate than membrane theory in studying wave propagation, and the bending effect plays an important role in certain wave modes. Effects of pressure, axial pre-stretch, and fiber angle on dispersion relations are also discussed.
JOURNAL OF SOUND AND VIBRATION
(2021)
Article
Engineering, Multidisciplinary
Patrick E. Farrell, Luis F. Gatica, Bishnu P. Lamichhane, Ricardo Oyarzua, Ricardo Ruiz-Baier
Summary: The study presents a mixed finite element method adapted from the three-field formulation for hyperelastic materials, showing high numerical efficiency and convergence properties. The method exhibits good numerical performance and physical fidelity when dealing with incompressibility constraints in solid mechanics.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2021)
Article
Engineering, Mechanical
Suhib Abu-Qbeitah, Mahmood Jabareen, Konstantin Y. Volokh
Summary: In this study, a finite element formulation is developed to model quasi-static crack propagation in hyperelastic solids using the material-sink approach. Breakage of molecular bonds leads to material separation and appearance of new crack surfaces. The diffusion of bond breakage causes localized material loss. To account for this, mass density is considered as a variable that decreases in the damaged area. Mathematically, mass balance is included as an additional law to regularize the computational model. The developed finite element formulation has displacement and density degrees of freedom and a monolithic approach is applied for stable solution of the nonlinear problem. Numerical examples demonstrate the robustness of the proposed approach for modeling aneurysm material fracture.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2023)
Article
Materials Science, Multidisciplinary
Stephan Teichtmeister, Gerhard A. Holzapfel
Summary: This study focuses on modeling cross-links in collagenous tissues and proposes a planar continuum model to characterize their mechanical properties. By considering dispersed fibers and randomly distributed cross-links, the study reveals the mechanical behavior of these tissues. The findings provide important insights into the microstructural mechanisms in semi-flexible biopolymer gels.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2022)
Article
Chemistry, Multidisciplinary
Hegeng Li, Hongzhen Liu, Mingze Sun, YongAn Huang, Lizhi Xu
Summary: Recent advancements in soft functional materials have provided opportunities for developing bioelectronic devices with tissue-like mechanical properties. These devices, when integrated into the human body, could offer advanced sensing and stimulation for medical purposes. The challenge lies in creating 3D interfaces between soft electronic tools and complex biological organs and tissues, with various innovative approaches being explored to address this issue, promising opportunities for further scientific research and technological innovation.
ADVANCED MATERIALS
(2021)
Article
Biophysics
Jonas F. Eichinger, Maximilian J. Grill, Iman Davoodi Kermani, Roland C. Aydin, Wolfgang A. Wall, Jay D. Humphrey, Christian J. Cyron
Summary: The study presents a novel computational framework based on the finite element method to simulate key mechanobiological mechanisms of mechanical homeostasis. The framework replicates many experimental observations on short time scales, providing a systematic tool for future research on mechanical homeostasis.
BIOMECHANICS AND MODELING IN MECHANOBIOLOGY
(2021)
Article
Engineering, Biomedical
Takashi Funai, Hiroyuki Kataoka, Hideo Yokota, Taka-Aki Suzuki
Summary: This study proposes a strain-energy function that ensures a monotonically increasing trend of stress-strain relationships for biological soft tissues. By using the convexity of invariants, a polyconvex form of the function was derived to reproduce the desired trend, and its applicability was confirmed through curve fitting with different biological soft tissues.
BIO-MEDICAL MATERIALS AND ENGINEERING
(2021)
Article
Mechanics
Shiheng Zhao, Zheng Chang
Summary: In this study, a model of linear elastic wave propagation in a finitely pre-stretched soft fiber was established based on the small-on-large theory, with the longitudinal (L-) and transverse (T-) wave velocities being validated. It was found that the variation of L-wave velocity with increasing pre-stress depends on the concavity of the stress-strain curve, while the increase of T-wave velocity is independent of constitutive models. The study also revealed that the velocities of both L- and T-waves are more significantly affected in compressible fibers compared to nearly-incompressible ones.
INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES
(2021)
Article
Materials Science, Multidisciplinary
Felipe T. Stumpf, Gustavo L. F. Gotz, Daniel M. De Leon
Summary: In this work, a parametric optimization framework is developed to deal with fiber-reinforced elastomeric matrices. The main goal is to study the efficiency of a local-based derivative-free algorithm in the optimization of problems considering finite deformation and material nonlinearity assumptions in fiber composite design. The methodology can easily be implemented in existing finite element codes and the results show the pros and cons of both types of optimization.
MECHANICS OF MATERIALS
(2023)
Article
Engineering, Biomedical
Jonas F. Eichinger, Daniel Paukner, Roland C. Aydin, Wolfgang A. Wall, Jay D. Humphrey, Christian J. Cyron
Summary: Cells in soft biological tissues regulate the mechanical state of the extracellular matrix to ensure structural integrity and functionality, known as mechanical homeostasis. This process plays a crucial role in diseases like aneurysms and cancer. By combining experiments, computer simulations, and theoretical analysis, a likely candidate for the target quantity that cells regulate has been identified on short time scales and in simplified tissue models.
ACTA BIOMATERIALIA
(2021)
Article
Multidisciplinary Sciences
Chunxiang Wang, Yingdan Wu, Xiaoguang Dong, Milena Armacki, Metin Sitti
Summary: Compared with conventional medical imaging, implanted electronic sensors can continuously monitor advanced physiological properties of soft biological tissues. However, they are invasive and could cause inflammation. Here, we propose a minimally invasive method using wireless miniature soft robots to sense tissue physiological properties in situ. By controlling robot-tissue interaction with external magnetic fields, tissue properties can be recovered precisely from robot shape and magnetic fields, as visualized by medical imaging. We demonstrate that the robot can traverse tissues with multimodal locomotion and sense adhesion, pH, and viscoelasticity on ex vivo porcine and mice gastrointestinal tissues, tracked by x-ray or ultrasound imaging.
Article
Biophysics
Alireza Jafarinia, Gian Marco Melito, Thomas Stephan Mueller, Malte Rolf-Pissarczyk, Gerhard A. A. Holzapfel, Guenter Brenn, Katrin Ellermann, Thomas Hochrainer
Summary: The morphological parameters of the dissected aorta, including the false lumen (FL) diameter and the size and location of intimal tears, play a crucial role in the formation of FL thrombosis in Type B aortic dissection (TBAD). When the FL diameter is larger than the true lumen diameter, there is a higher risk of partial thrombosis. Additionally, a higher ratio of distal to proximal tear size increases the risk of FL patency. These parameters are important in classifying the morphology of FL into patent, partially thrombosed, and fully thrombosed.
BIOMECHANICS AND MODELING IN MECHANOBIOLOGY
(2023)
Article
Engineering, Biomedical
Emmanouil Agrafiotis, Christian Mayer, Martin Grabenwoeger, Daniel Zimpfer, Peter Regitnig, Heinrich Maechler, Gerhard A. Holzapfel
Summary: This study examined the effects of thoracic endovascular repair (TEVAR) on the biomechanical properties of the aorta. It found that TEVAR resulted in reduced aortic distensibility, stiffness mismatch, and histological remodeling of the aortic wall. These findings have implications for improving stent-graft design and minimizing complications.
ACTA BIOMATERIALIA
(2023)
Article
Engineering, Biomedical
Anna Pukaluk, Heimo Wolinski, Christian Viertler, Peter Regitnig, Gerhard A. Holzapfel, Gerhard Sommer
Summary: This study focuses on the changes in collagen and elastin microstructure in the aortic adventitia under macroscopic equibiaxial loading. The results show that collagen fibers in the adventitia divide into two families under loading, while elastin fibers do not show clear orientation. These findings provide important insights into the stretching process of the aortic wall.
ACTA BIOMATERIALIA
(2023)
Article
Engineering, Biomedical
Francesco Giovanniello, Meisam Asgari, Ivan D. Breslavsky, Giulio Franchini, Gerhard A. Holzapfel, Maryam Tabrizian, Marco Amabili
Summary: In this study, scaffolds with ideal static and dynamic mechanical properties, similar to natural human aortas, were successfully obtained through an optimized decellularization protocol. This provides an ideal choice for developing innovative aortic grafts.
ACTA BIOMATERIALIA
(2023)
Article
Engineering, Multidisciplinary
Kevin Linka, Adrian Buganza Tepole, Gerhard A. Holzapfel, Ellen Kuhl
Summary: Choosing the best constitutive model and parameters in continuum mechanics has traditionally relied on user experience and preference. This paper proposes a new method that autonomously discovers the best model and parameters to explain experimental data using a neural network. The method is robust and satisfies physical constraints, and has the potential to revolutionize the field of constitutive modeling. Evaluation: 8 points
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2023)
Article
Engineering, Multidisciplinary
Will Zhang, Javiera Jilberto, Gerhard Sommer, Michael S. Sacks, Gerhard A. Holzapfel, David A. Nordsletten
Summary: Biomechanics is important in diagnosing and treating heart conditions. Computational models can provide personalized treatment options but require accurate constitutive equations for biomechanical behavior prediction. A fractional viscoelastic modeling approach that accurately captures the viscoelastic response of the human myocardium was previously developed. This approach has comparable computational costs and only requires two additional material parameters. In this study, the implementation of this approach in Finite Element Analysis was presented, numerical properties were examined, and the physiological implications were explored.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2023)
Article
Biotechnology & Applied Microbiology
Manuel P. Kainz, Alexander Greiner, Jan Hinrichsen, Dagmar Kolb, Ester Comellas, Paul Steinmann, Silvia Budday, Michele Terzano, Gerhard A. Holzapfel
Summary: A novel nonlinear poro-viscoelastic computational model based on the Theory of Porous Media was proposed to describe the mechanical response of brain tissue. Indentation experiments were conducted on a tailor-made hydrogel mimicking brain tissue, and an inverse parameter identification scheme was used to extract the optimal constitutive model parameters. The model was validated through finite element simulations.
FRONTIERS IN BIOENGINEERING AND BIOTECHNOLOGY
(2023)
Review
Cardiac & Cardiovascular Systems
Colton J. Ross, Arshid Mir, Harold M. Burkhart, Gerhard A. Holzapfel, Chung-Hao Lee
Summary: Hypoplastic Left Heart Syndrome (HLHS) is a congenital heart defect that requires a three-stage surgical palliation. Tricuspid regurgitation (TR) occurs in 25% of patients undergoing this procedure and is associated with increased mortality risk. Valvular anomalies and geometric properties are identified as the main predictors for poor prognosis in HLHS patients with TR. Future studies should focus on engineering-based metrics, multivariate analysis, and predictive models to determine the predictors of TR onset during the three palliation stages. These efforts will lead to the development of innovative tools for surgical timing decisions, prophylactic surgical valve repair, and improvement of current intervention techniques.
JOURNAL OF CARDIOVASCULAR DEVELOPMENT AND DISEASE
(2023)
Article
Engineering, Biomedical
Will Zhang, Majid Jadidi, Sayed Ahmadreza Razian, Gerhard A. Holzapfel, Alexey Kamenskiy, David A. Nordsletten
Summary: This study introduces a new viscoelastic constitutive model for the human femoropopliteal artery, which accurately describes its mechanical characteristics and time-dependent behavior. The model improves the accuracy of computational simulations and expands our knowledge of arterial mechanophysiology.
ACTA BIOMATERIALIA
(2023)
Article
Engineering, Biomedical
Federica Cosentino, Selda Sherifova, Gerhard Sommer, Giuseppe Raffa, Michele Pilato, Salvatore Pasta, Gerhard A. Holzapfel
Summary: This study investigates regional differences in ascending thoracic aortic aneurysms (ATAAs) in humans, highlighting the impact of fiber dispersion on microstructural properties and providing important biomechanical data for improving current risk stratification strategies.
ACTA BIOMATERIALIA
(2023)
Article
Engineering, Biomedical
Mohammad Javad Sadeghinia, Hans Martin Aguilera, Stig Urheim, Robert Matongo Persson, Vegard Skalstad Ellensen, Rune Haaverstad, Gerhard A. Holzapfel, Bjorn Skallerud, Victorien Prot
Summary: This study examines the mechanical behavior of Barlow and FED tissue by using biaxial mechanical tests and second harmonic generation microscopy. The results show that the Barlow sample and the most affected FED sample have different mechanical behavior and collagen structure compared to the other FED samples. The finite element model constructed based on this study shows good agreement with echocardiography and provides essential data for understanding the relationship between collagen microstructure and degenerative mitral valve mechanics.
ACTA BIOMATERIALIA
(2023)
Article
Mechanics
Daniel Ch. Haspinger, Gerhard A. Holzapfel
Summary: This study systematically analyzes the descriptive and predictive capabilities of the GST and AI approaches for modeling arterial mechanical behavior. Results show that there is no statistically significant difference in the descriptive features and minor deviations in the predictive aspects of the two modeling approaches.
EUROPEAN JOURNAL OF MECHANICS A-SOLIDS
(2023)
Article
Materials Science, Multidisciplinary
Maximilian P. Wollner, Michele Terzano, Malte Rolf-Pissarczyk, Gerhard A. Holzapfel
Summary: This article develops a material model capable of reproducing anisotropy, viscoelasticity, stress softening, and permanent set by merging several pre-existing frameworks. Each constitutive effect is discussed separately in terms of its thermodynamics and mechanical interpretation and successively built on top of each other. The pseudo-elastic approach to permanent set occupies a special place in the formulation, with a novel discussion of its applicability to generic deformations. The capabilities and possible shortcomings of the formulation are highlighted and a simple numerical algorithm for stress computation is presented.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2023)
Article
Multidisciplinary Sciences
Misael Dalbosco, Michele Terzano, Thiago A. Carniel, Eduardo A. Fancello, Gerhard A. Holzapfel
Summary: This study presents a multi-scale computational analysis of abdominal aortic aneurysms (AAAs), which suggests that the formation of aneurysms disrupts the micro-mechanics of healthy tissue and triggers collagen growth and remodeling through mechanosensing cells. This leads to changes in the macro-mechanics and microstructure of the tissue at a cellular scale.
JOURNAL OF THE ROYAL SOCIETY INTERFACE
(2023)
Article
Multidisciplinary Sciences
Michele Terzano, Maximilian P. Wollner, Manuel P. Kainz, Malte Rolf-Pissarczyk, Nils Gotzen, Gerhard A. Holzapfel
Summary: In situ tissue engineering provides a innovative solution for replacing valves and grafts in cardiovascular medicine. The mechanical behavior of the polymeric scaffold and its short-term response are studied using simulations and experiments.
JOURNAL OF THE ROYAL SOCIETY INTERFACE
(2023)
