Mechanics of human vocal folds layers during finite strains in tension, compression and shear

Abstract

During phonation, human vocal fold tissues are subjected to combined tension, compression and shear loadings modes from small to large finite strains. Their mechanical behaviour is however still not well understood.Herein, we complete the existing mechanical database of these soft tissues, by characterising, for the first time, the cyclic and finite strains behaviour of the lamina propria and vocalis layers under these loading modes. To minimise the inter or intra-individual variability, particular attention was paid to subject each tissue sample successively to the three loadings. A nonlinear mechanical behaviour is observed for all loading modes : a J-shape strain stiffening in longitudinal tension and transverse compression, albeit far less pronounced in shear, stress accommodation and stress hysteresis whatever the loading mode. In addition, recorded stress levels during longitudinal tension are much higher for the lamina propria than for the vocalis.Conversely, the responses of the lamina propria and the vocalis in transverse compression as well as transverse and longitudinal shears are of the same orders of magnitude. We also highlight the strain rate sensitivity of the tissues, as well as their anisotropic properties.

Dynamic Biomechanical Analysis of Vocal Folds Using Pipette Aspiration Technique

“…Results issued by Cochereau et al [ 27 ] also show different elasticity between VF pairs in tension measurements and thus substantiate our results. We want to point out that this conclusion is based on the measurement of three larynges and does not have the statistical power to make general claims.…”

A micro-mechanical model for the fibrous tissues of vocal folds

“…The identification of the histo-mechanical parameters of the model was performed by adjusting its predictions to biomechanical data recently acquired on human vocal-fold tissues [20]. To do so, a representative set of lamina propria and vocalis sublayers (hereinafter noted as LP i and V i , i ∈ [1,2]) was selected from the reported database.…”

“…Despite the considerable progress made in 3D microimaging [43,52,18,73,51,32,3,48], vocal folds, along with their fibrous architectures, are hardly observable in vivo [71,23]. Although a large biomechanical database has been collected on excised vocal folds over the last twenty years [17,87,49,74,16,20], the 3D microscale rearrangement of the loaded tissues is still to be explored. Conversely, the development of macroscopic (tissue scale) or micro-mechanical (fiber scale) models of phonation is a promising alternative to gain an in-depth understanding of the vocal-fold biomechanics : • In macroscopic approaches, phenomenological exponential and power-law functions are commonly proposed to describe the stressstrain responses typically observed when deforming soft biological tissues [6,45,46,58,59,72].…”

“…Within this context, the present work proposes a micro-mechanical model able to reproduce the nonlinear anisotropic mechanical properties of vocal-fold layers (i.e., lamina propria, vocalis) subjected to multiaxial finite strains, from the knowledge of their 3D fibrous architecture. It combines the use of ex vivo database acquired on human vocal-fold microstructures over the past ten years, with a recent study on their finite strain macroscale mechanics in longitudinal tension, as well as transverse compression and longitudinal shear [20]. The paper is structured as follows.…”

Soft Contact Mechanics with Gradient-Stiffness Surfaces

“…However, cells and tissues often exhibit a layered, or laminate, structure . This structure can facilitate a variety of functions including mass transport, − thermal insulation, and managing mechanical stress. , One system of particular interest is that of the eye: the tough sclera maintains the intraocular pressure, but that mechanically strong tissue is topped with the more compliant layer of stratified epithelial cells, which is again topped by flexible microvilli and glycocalyx, finally manifesting in the viscous, aqueous gel of the tear film (Figure A). From a mechanical perspective, the monotonic increase in compliance through these layers can be considered a gradient of stiffness decreasing toward the outer surface.…”