An indentation-based approach to determine the elastic constants of soft anisotropic tissues

Moghaddam, Amir Ostadi; Wei, Jie; Kim, Jiho; Dunn, Alison C.; Johnson, Amy J. Wagoner

doi:10.1016/j.jmbbm.2019.103539

Cited by 20 publications

(10 citation statements)

References 42 publications

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“…Often, complementary bulk tests, complicated data analysis, and specialized equipment are also required for the characterization, e.g., 41 . Our previous work 42 presented a simple indentation-based approach for the characterization of soft anisotropic tissues, but it was limited to mm-scale indenters, and thus, unsuitable for microscale characterization. While the indentation modulus provides a useful estimate of the mechanical properties, anisotropic characterization at microscale may provide further insights into the tissue microstructure and micromechanics.…”

Section: Discussionmentioning

confidence: 99%

An optomechanogram for assessment of the structural and mechanical properties of tissues

Lee

Moghaddam

Shen

et al. 2021

Sci Rep

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The structural and mechanical properties of tissue and the interplay between them play a critical role in tissue function. We introduce the optomechanogram, a combined quantitative and qualitative visualization of spatially co-registered measurements of the microstructural and micromechanical properties of any tissue. Our approach relies on the co-registration of two independent platforms, second-harmonic generation (SHG) microscopy for quantitative assessment of 3D collagen-fiber microstructural organization, and nanoindentation (NI) for local micromechanical properties. We experimentally validate our method by applying to uterine cervix tissue, which exhibits structural and mechanical complexity. We find statistically significant agreement between the micromechanical and microstructural data, and confirm that the distinct tissue regions are distinguishable using either the SHG or NI measurements. Our method could potentially be used for research in pregnancy maintenance, mechanobiological studies of tissues and their constitutive modeling and more generally for the optomechanical metrology of materials.

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Section: Discussionmentioning

confidence: 99%

An optomechanogram for assessment of the structural and mechanical properties of tissues

Lee

Moghaddam

Shen

et al. 2021

Sci Rep

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“…However, previous studies have focused isotropic materials. With anisotropic materials (such as fiber-reinforced, rock and rock mass materials, carbon/carbon composites, engineer steels etc) widely applied in engineering, it is necessary to extend indentation measurement to anisotropic fields [26][27][28][29][30][31][32]. Currently, on the one hand, the indentation theory of isotropic materials has extended to anisotropic materials, and some theoretical studies have been conducted [33][34][35][36][37][38][39].…”

Section: Introductionmentioning

confidence: 99%

Measuring elastic parameters of transversely isotropic materials by cylindrical indentation

Liao

Xie

2023

Meas. Sci. Technol.

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Based on the cylindrical indention experiments, a novel model has been established to characterize the elastic mechanical property of transversely isotropic materials. In the first place, the influences of different loading orientations for indentation, and elastic parameters of materials on the indentation modulus of transversely isotropic materials are analyzed by means of theoretical and dimensional analysis. In the second place, three dimensional (3D) indentation experiments that encompass the wide range of transversely isotropic material parameters are simulated by finite element (FE) approach. Each quantity (transversely isotropic Young’s modulus, EP, longitudinal Young’s modulus, EL, longitudinal shear modulus, GL, and loading orientation angle, ) how affects the normalized indentation modulus is investigated. Then, the dimensionless analytical relationship between indentation modulus and elastic parameters is put up at three different indentation orientation angles . To prove the correctness of the proposed model, several groups of transversely isotropic materials are selected as input parameters to carry out indentation numerical experiments and the error analysis is made in detail. Simultaneously, the technique is specialized to the particular case of a Zinc single crystal material to verify the accuracy of these formulas derived. These good agreements show that the proposed method is reliable and it could be used to quantify the elastic parameters of the transversely isotropic materials.

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“…Combined viscoelasticity and poroelasticity models have been applied with success; however, complications arise when considering possible interdependencies of these properties, and most necessarily assume isotropy of the sample. Another approach is to treat the sample as continuous but orthotropic, which can describe fiber-reinforced materials. Properties of very compliant or biologically derived samples can be fit with these models given the volume being probed is sufficiently small to be described by a particular, homogeneous constitutive response.…”

Section: Introductionmentioning

confidence: 99%

Soft Contact Mechanics with Gradient-Stiffness Surfaces

2022

Self Cite

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The stiffness in the top surface of many biological entities like cornea or articular cartilage, as well as chemically cross-linked synthetic hydrogels, can be significantly lower or more compliant than the bulk. When such a heterogeneous surface comes into contact, the contacting load is distributed differently from typical contact models. The mechanical response under indentation loading of a surface with a gradient of stiffness is a complex, integrated response that necessarily includes the heterogeneity. In this work, we identify empirical contact models between a rigid indenter and gradient elastic surfaces by numerically simulating quasi-static indentation. Three key case studies revealed the specific ways in which (I) continuous gradients, (II) laminate-layer gradients, and (III) alternating gradients generate new contact mechanics at the shallow-depth limit. Validation of the simulation-generated models was done by micro- and nanoindentation experiments on polyacrylamide samples synthesized to have a softer gradient surface layer. The field of stress and stretch in the subsurface as visualized from the simulations also reveals that the gradient layers become confined, which pushes the stretch fields closer to the surface and radially outward. Thus, contact areas are larger than expected, and average contact pressures are lower than predicted by the Hertz model. The overall findings of this work are new contact models and the mechanisms by which they change. These models allow a more accurate interpretation of the plethora of indentation data on surface gradient soft matter (biological and synthetic) as well as a better prediction of the force response to gradient soft surfaces. This work provides examples of how gradient hydrogel surfaces control the subsurface stress distribution and loading response.

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An indentation-based approach to determine the elastic constants of soft anisotropic tissues

Cited by 20 publications

References 42 publications

An optomechanogram for assessment of the structural and mechanical properties of tissues

An optomechanogram for assessment of the structural and mechanical properties of tissues

Measuring elastic parameters of transversely isotropic materials by cylindrical indentation

Soft Contact Mechanics with Gradient-Stiffness Surfaces

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