scholarly journals Poisson's Contraction and Fiber Kinematics in Tissue: Insight From Collagen Network Simulations

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
R. C. Picu ◽  
S. Deogekar ◽  
M. R. Islam
Keyword(s):  
Mouse Skin ◽  
Tissue Mechanics ◽  
Collagen Gels ◽  
Fiber Network ◽  
Collagen Orientation ◽  
Strain Behavior ◽  
Small Strains ◽  
Confining Effect ◽  
Highly Nonlinear ◽  
Network Simulations

Connective tissue mechanics is highly nonlinear, exhibits a strong Poisson's effect, and is associated with significant collagen fiber re-arrangement. Although the general features of the stress–strain behavior have been discussed extensively, the Poisson's effect received less attention. In general, the relationship between the microscopic fiber network mechanics and the macroscopic experimental observations remains poorly defined. The objective of the present work is to provide additional insight into this relationship. To this end, results from models of random collagen networks are compared with experimental data on reconstructed collagen gels, mouse skin dermis, and the human amnion. Attention is devoted to the mechanism leading to the large Poisson's effect observed in experiments. The results indicate that the incremental Poisson's contraction is directly related to preferential collagen orientation. The experimentally observed downturn of the incremental Poisson's ratio at larger strains is associated with the confining effect of fibers transverse to the loading direction and contributing little to load bearing. The rate of collagen orientation increases at small strains, reaches a maximum, and decreases at larger strains. The peak in this curve is associated with the transition of the network deformation from bending dominated, at small strains, to axially dominated, at larger strains. The effect of fiber tortuosity on network mechanics is also discussed, and a comparison of biaxial and uniaxial loading responses is performed.

3D network simulations of paper structure

2012 ◽  
Vol 27 (2) ◽  
pp. 256-263 ◽  
Author(s):  
S. Lavrykov ◽  
B. V. Ramarao ◽  
S. B. Lindström ◽  
K. M. Singh
Keyword(s):  
Fiber Network ◽  
Small Strains ◽  
Simulation Techniques ◽  
3D Network ◽  
Sheet Structure ◽  
Network Simulations ◽  
Fiber Dimensions ◽  
Pressing Operation ◽  
Paper Structure ◽  
The Impact

Abstract The structure of paper influences its properties and simulations of it are necessary to understand the impact of fiber and papermaking conditions on the sheet properties. We show a method to develop a representative structure of paper by merging different simulation techniques for the forming section and the pressing operation. The simulation follows the bending and drape of fibers over one another in the final structure and allows estimation of sheet properties without recourse to arbitrary bending rules or experimental measurements of density and/or RBA. Fibers are first modeled as jointed beams following the fluid mechanics in the forming section. The sheet structure obtained from this is representative of the wet sheet from the couch. The pressing simulation discretizes fibers into a number of solid elements around the lumen. Bonding between fibers is simulated using spring elements. The resulting fiber network was analyzed to determine its elastic modulus and deformation under small strains. The influence of fiber dimensions, namely fiber lengths, widths and thicknesses as well as bond stiffnesses on the elasticity of the network are studied. A brief account of inclusion of fines, represented by individual cubical elements is also shown.

scholarly journals Percolation of collagen stress in a random network model of the alveolar wall

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dylan T. Casey ◽  
Samer Bou Jawde ◽  
Jacob Herrmann ◽  
Vitor Mori ◽  
J. Matthew Mahoney ◽  
...  
Keyword(s):  
Connective Tissue ◽  
Network Model ◽  
Random Network ◽  
Collagen Fibers ◽  
Tissue Mechanics ◽  
Alveolar Wall ◽  
Stress Strain ◽  
Fiber Network ◽  
Strain Behavior ◽  
Nonlinear Stress

AbstractFibrotic diseases are characterized by progressive and often irreversible scarring of connective tissue in various organs, leading to substantial changes in tissue mechanics largely as a result of alterations in collagen structure. This is particularly important in the lung because its bulk modulus is so critical to the volume changes that take place during breathing. Nevertheless, it remains unclear how fibrotic abnormalities in the mechanical properties of pulmonary connective tissue can be linked to the stiffening of its individual collagen fibers. To address this question, we developed a network model of randomly oriented collagen and elastin fibers to represent pulmonary alveolar wall tissue. We show that the stress–strain behavior of this model arises via the interactions of collagen and elastin fiber networks and is critically dependent on the relative fiber stiffnesses of the individual collagen and elastin fibers themselves. We also show that the progression from linear to nonlinear stress–strain behavior of the model is associated with the percolation of stress across the collagen fiber network, but that the location of the percolation threshold is influenced by the waviness of collagen fibers.

scholarly journals Lung tissue mechanics as an emergent phenomenon

2011 ◽  
Vol 110 (4) ◽  
pp. 1111-1118 ◽  
Author(s):  
Béla Suki ◽  
Jason H. T. Bates
Keyword(s):  
Mechanical Behavior ◽  
Lung Tissue ◽  
Computational Models ◽  
Tissue Mechanics ◽  
Dynamic Interactions ◽  
Strain Behavior ◽  
Tissue Resistance ◽  
Highly Nonlinear ◽  
Nonlinear Stress ◽  
Macro Scale

The mechanical properties of lung parenchymal tissue are both elastic and dissipative, as well as being highly nonlinear. These properties cannot be fully understood, however, in terms of the individual constituents of the tissue. Rather, the mechanical behavior of lung tissue emerges as a macroscopic phenomenon from the interactions of its microscopic components in a way that is neither intuitive nor easily understood. In this review, we first consider the quasi-static mechanical behavior of lung tissue and discuss computational models that show how smooth nonlinear stress-strain behavior can arise through a percolation-like process in which the sequential recruitment of collagen fibers with increasing strain causes them to progressively take over the load-bearing role from elastin. We also show how the concept of percolation can be used to link the pathologic progression of parenchymal disease at the micro scale to physiological symptoms at the macro scale. We then examine the dynamic mechanical behavior of lung tissue, which invokes the notion of tissue resistance. Although usually modeled phenomenologically in terms of collections of springs and dashpots, lung tissue viscoelasticity again can be seen to reflect various types of complex dynamic interactions at the molecular level. Finally, we discuss the inevitability of why lung tissue mechanics need to be complex.

Polarized Light Microscopy for Analyzing Tissue Mechanics During In Vitro Acupuncture

2008 ◽  
Author(s):  
Lowell Taylor Edgar ◽  
Margaret Julias ◽  
David I. Shreiber ◽  
Helen M. Buettner
Keyword(s):  
Connective Tissue ◽  
Light Microscopy ◽  
Type I Collagen ◽  
Polarized Light ◽  
Tissue Mechanics ◽  
Polarized Light Microscopy ◽  
Tissue Response ◽  
Type I ◽  
Collagen Gels

Acupuncture is a traditional therapy originating in China almost 2000 years ago. Acupuncture has slowly been growing in popularity in the West, and clinical evidence has shown the potential for acupuncture as a low-cost ‘alternative’ therapy for an assortment of ailments [1]. The practice of acupuncture involves inserting fine needles into the skin followed by needle manipulation, usually by rotation. Recent studies by Langevin et al demonstrate that this rotation causes the subcutaneous connective tissue to couple to and wind around the needle [2–4], which suggests that mechanotransduction in the connective tissue might play a role in the therapeutic mechanisms that underlay acupuncture [2, 3]. To begin to decompose and quantify this complex mechanism at the tissue level in a controlled setting, we have simulated acupuncture in type I collagen gels in vitro, and have developed algorithms to quantify the tissue response following imaging with polarized light microscopy (PLM).

On the Biaxial Mechanical Response of Porcine Tricuspid Valve Leaflets

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Keyvan Amini Khoiy ◽  
Rouzbeh Amini
Keyword(s):  
Tricuspid Valve ◽  
Computational Models ◽  
Mechanical Response ◽  
Ex Vivo ◽  
Biaxial Stress ◽  
Strain Behavior ◽  
Highly Nonlinear ◽  
Rapid Transition ◽  
Biaxial Tensile Testing ◽  
The Right

Located on the right side of the heart, the tricuspid valve (TV) prevents blood backflow from the right ventricle to the right atrium. Similar to other cardiac valves, quantification of TV biaxial mechanical properties is essential in developing accurate computational models. In the current study, for the first time, the biaxial stress–strain behavior of porcine TV was measured ex vivo under different loading protocols using biaxial tensile testing equipment. The results showed a highly nonlinear response including a compliant region followed by a rapid transition to a stiff region for all of the TV leaflets both in the circumferential and in the radial directions. Based on the data analysis, all three leaflets were found to be anisotropic, and they were stiffer in the circumferential direction in comparison to the radial direction. It was also concluded that the posterior leaflet was the most anisotropic leaflet.

Mechanical properties and mechanical behavior of (SiO2)f/SiO2 composites with 3D six-directional braided quartz fiber preform

2012 ◽  
Vol 19 (2) ◽  
pp. 113-117 ◽  
Author(s):  
Yong Liu ◽  
Zhaofeng Chen ◽  
Jianxun Zhu ◽  
Yun Jiang ◽  
Binbin Li
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Thermal Structure ◽  
Three Dimensional ◽  
Shear Loading ◽  
Failure Behavior ◽  
Fiber Volume ◽  
Strain Behavior ◽  
Highly Nonlinear ◽  
Nonlinear Stress

Abstract(SiO2)f/SiO2 composites reinforced with three-dimensional (3D) six-directional preform were fabricated by the silicasol-infiltration-sintering method. The nominal fiber volume fraction was 47%. To characterize the mechanical properties of the composites, mechanical testing was carried out under various loading conditions, including tensile, flexural, and shear loading. The composite exhibited highly nonlinear stress-strain behavior under all the three types of loading. The results indicated that the 3D six-directional braided (SiO2)f/SiO2 composites exhibited superior flexural properties and good shear resistant as compared with other types of preform (2.5D and 3D four-directional)-reinforced (SiO2)f/SiO2 composites. 3D six-directional braided (SiO2)f/SiO2 composite exhibited graceful failure behavior under loading. The addition of 5th and 6th yarns resulted in controlled fracture and hence these 3D six-directional braided composites could possibly be suitable for thermal structure components.

scholarly journals Three-Dimensional Quantification of Collagen Microstructure During Tensile Mechanical Loading of Skin

2021 ◽  
Vol 9 ◽  
Author(s):  
Alan E. Woessner ◽  
Jake D. Jones ◽  
Nathan J. Witt ◽  
Edward A. Sander ◽  
Kyle P. Quinn
Keyword(s):  
Mechanical Loading ◽  
Collagen Fiber ◽  
Volume Fraction ◽  
Second Harmonic ◽  
Three Dimensional ◽  
Mouse Skin ◽  
3D Analysis ◽  
Tissue Deformation ◽  
Fiber Network ◽  
Micro Scale

Skin is a heterogeneous tissue that can undergo substantial structural and functional changes with age, disease, or following injury. Understanding how these changes impact the mechanical properties of skin requires three-dimensional (3D) quantification of the tissue microstructure and its kinematics. The goal of this study was to quantify these structure-function relationships via second harmonic generation (SHG) microscopy of mouse skin under tensile mechanical loading. Tissue deformation at the macro- and micro-scale was quantified, and a substantial decrease in tissue volume and a large Poisson’s ratio was detected with stretch, indicating the skin differs substantially from the hyperelastic material models historically used to explain its behavior. Additionally, the relative amount of measured strain did not significantly change between length scales, suggesting that the collagen fiber network is uniformly distributing applied strains. Analysis of undeformed collagen fiber organization and volume fraction revealed a length scale dependency for both metrics. 3D analysis of SHG volumes also showed that collagen fiber alignment increased in the direction of stretch, but fiber volume fraction did not change. Interestingly, 3D fiber kinematics was found to have a non-affine relationship with tissue deformation, and an affine transformation of the micro-scale fiber network overestimates the amount of fiber realignment. This result, along with the other outcomes, highlights the importance of accurate, scale-matched 3D experimental measurements when developing multi-scale models of skin mechanical function.

scholarly journals Micromechanics of cellularized biopolymer networks

2015 ◽  
Vol 112 (37) ◽  
pp. E5117-E5122 ◽  
Author(s):  
Christopher A. R. Jones ◽  
Matthew Cibula ◽  
Jingchen Feng ◽  
Emma A. Krnacik ◽  
David H. McIntyre ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Optical Tweezers ◽  
Collagen Fiber ◽  
Type I Collagen ◽  
Qualitative Difference ◽  
Type I ◽  
Dependent Manner ◽  
Adhesion Forces ◽  
Collagen Gels ◽  
Fiber Network

Collagen gels are widely used in experiments on cell mechanics because they mimic the extracellular matrix in physiological conditions. Collagen gels are often characterized by their bulk rheology; however, variations in the collagen fiber microstructure and cell adhesion forces cause the mechanical properties to be inhomogeneous at the cellular scale. We study the mechanics of type I collagen on the scale of tens to hundreds of microns by using holographic optical tweezers to apply pN forces to microparticles embedded in the collagen fiber network. We find that in response to optical forces, particle displacements are inhomogeneous, anisotropic, and asymmetric. Gels prepared at 21 °C and 37 °C show qualitative difference in their micromechanical characteristics. We also demonstrate that contracting cells remodel the micromechanics of their surrounding extracellular matrix in a strain- and distance-dependent manner. To further understand the micromechanics of cellularized extracellular matrix, we have constructed a computational model which reproduces the main experiment findings.

Collagen-Agarose Co-Gels as a Model for Collagen-Matrix Interaction in Soft Tissue

2011 ◽  
Author(s):  
Spencer P. Lake ◽  
Sadie Doggett ◽  
Victor H. Barocas
Keyword(s):  
Collagen Fiber ◽  
Type I Collagen ◽  
Soft Tissues ◽  
Experimental System ◽  
Model System ◽  
Type I ◽  
Collagen Gels ◽  
Fiber Network ◽  
Fibrillar Material

Connective soft tissues have complex mechanical properties that are determined by their collagen fiber network and surrounding non-fibrillar material. The mechanical role of non-fibrillar material and the nature of its interaction with the collagen network remain poorly understood, in part because of the lack of a simple experimental model system to examine and quantify these properties. The development of a simple but representational experimental system will allow for greater insight into the interaction between fibers and the non-fibrillar matrix. Reconstituted Type I collagen gels are an attractive model tissue for exploring micro- and macroscale relationships between constituents (e.g., [1–2]), but standard collagen gels lack the non-fibrillar components (i.e., proteoglycan, minor collagens, etc.) present in native tissue. A recent study [3] added low quantities of agarose to collagen gels, which dramatically increased the shear storage modulus with minimal changes to the collagen fiber network. In this study, we suggest that collagen-agarose co-gels can serve as a model system to investigate the mechanical role of non-fibrillar ECM. Even though agarose is relatively compliant at low concentrations, and collagen fibers are very stiff in tension, we hypothesized that the presence of agarose in co-gels would have a pronounced effect on structural response and mechanical behavior in tensile loading. Therefore, the objective of this study was to examine the properties of collagen-agarose co-gels to understand better the nature of, and the relationships between, the collagen fiber network and non-fibrillar matrix of simplified tissue analogs.

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