SWISSMECH Seminar : Multiscale mechanics of human skin
Event details
| Date | 15.12.2022 |
| Hour | 16:00 › 17:00 |
| Speaker |
Prof. Edoardo Mazza Experimental Continuum Mechanics, ETH Zürich Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf |
| Location | Online |
| Category | Conferences - Seminars |
| Event Language | English |
Abstract: The mechanical properties of human skin are linked to its function at both tissue and cell length scale. In fact, the tissue has to provide sufficient compliance to enable body movements, but it also forms a mechanically stable barrier against external loads. At cell length scale, the mechanical properties of the extracellular matrix influence the behavior of dermal cells, e.g. during tissue repair and skin growth.
We combined ex-vivo multiaxial tensile experiments with in-vivo suction measurements and 3D tissue imaging in order to develop a multilayer poroelastic model of human skin. Each skin layer is represented as a biphasic material, with the solid part characterized by a fiber network and a compressible matrix, while interstitial fluid flow is driven by gradients of the chemical potential, which result from the boundary conditions imposed and the fixed charge distribution in the tissue. The corresponding mechanical response indicates an average stiffness akin to a modulus in the range of 100 kPa. However, testing on the macroscale does not allow characterizing the mechanical microenvironment of dermal cells, for which several orders of magnitude lower stiffness has been reported.
We rationalized the discrepancy between micro- and macroscale mechanics using a hybrid discrete-continuum model representative of the heterogeneous microstructure of the dermis. Fibers are modeled as nonlinear elastic connectors. Biphasic continuum elements provide a representation of interstitial fluid, proteoglycans and other non-collagenous ECM components. Model parameters were selected to provide a reasonable fit for experimental data at macro- and microscales.
The resulting multiscale model representation of skin allows to investigate the relationship between tissue microstructure and its fracture properties, and specifically to understand the deformation mechanisms contributing to its high defect tolerance. Moreover, simulation of skin stretch in-vivo provides quantitative information on the associated changes in cell-perceived stiffness and chemical potential of the interstitial fluid, and both are expected to influence the behavior of resident cells during skin homeostasis and repair.
We combined ex-vivo multiaxial tensile experiments with in-vivo suction measurements and 3D tissue imaging in order to develop a multilayer poroelastic model of human skin. Each skin layer is represented as a biphasic material, with the solid part characterized by a fiber network and a compressible matrix, while interstitial fluid flow is driven by gradients of the chemical potential, which result from the boundary conditions imposed and the fixed charge distribution in the tissue. The corresponding mechanical response indicates an average stiffness akin to a modulus in the range of 100 kPa. However, testing on the macroscale does not allow characterizing the mechanical microenvironment of dermal cells, for which several orders of magnitude lower stiffness has been reported.
We rationalized the discrepancy between micro- and macroscale mechanics using a hybrid discrete-continuum model representative of the heterogeneous microstructure of the dermis. Fibers are modeled as nonlinear elastic connectors. Biphasic continuum elements provide a representation of interstitial fluid, proteoglycans and other non-collagenous ECM components. Model parameters were selected to provide a reasonable fit for experimental data at macro- and microscales.
The resulting multiscale model representation of skin allows to investigate the relationship between tissue microstructure and its fracture properties, and specifically to understand the deformation mechanisms contributing to its high defect tolerance. Moreover, simulation of skin stretch in-vivo provides quantitative information on the associated changes in cell-perceived stiffness and chemical potential of the interstitial fluid, and both are expected to influence the behavior of resident cells during skin homeostasis and repair.
Practical information
- Informed public
- Registration required
- This event is internal
Organizer
- Prof. George Haller, ETHZ Prof. John Kolinski, EPFL