A biphasic multilayer computational model of human skin

David Sachs,Sebastian Kozerke,Edoardo Mazza,Adam Wahlsten,Gaetana Restivo

doi:10.1007/s10237-021-01424-w

Abstract

The present study investigates the layer-specific mechanical behavior of human skin. Motivated by skin’s histology, a biphasic model is proposed which differentiates between epidermis, papillary and reticular dermis, and hypodermis. Inverse analysis of ex vivo tensile and in vivo suction experiments yields mechanical parameters for each layer and predicts a stiff reticular dermis and successively softer papillary dermis, epidermis and hypodermis. Layer-specific analysis of simulations underlines the dominating role of the reticular dermis in tensile loading. Furthermore, it shows that the observed out-of-plane deflection in ex vivo tensile tests is a direct consequence of the layered structure of skin. In in vivo suction experiments, the softer upper layers strongly influence the mechanical response, whose dissipative part is determined by interstitial fluid redistribution within the tissue. Magnetic resonance imaging-based visualization of skin deformation in suction experiments confirms the deformation pattern predicted by the multilayer model, showing a consistent decrease in dermal thickness for large probe opening diameters.

Highlights

Understanding and correctly predicting the mechanical properties of human skin are essential for medical applications
In order to characterize the mechanical properties of skin in vivo, several methods were proposed such as suction (Müller et al 2018; Diridollou et al 1998, 2000; Barbarino et al 2011), indentation (Virén et al 2018; Abellan et al 2013; Iivarinen et al 2014) and in-situ tension (Flynn et al 2011; Bhushan et al 2010)
Model parameters for each layer were determined based on an iterative procedure aiming at representing ex vivo uniaxial as well as in vivo suction observations

Summary

Introduction

Understanding and correctly predicting the mechanical properties of human skin are essential for medical applications. Investigating and unveiling the underlying mechanical and mechanobiological processes require accurate models of the skin’s response under diverse conditions of mechanical loading. In order to characterize the mechanical properties of skin in vivo, several methods were proposed such as suction (Müller et al 2018; Diridollou et al 1998, 2000; Barbarino et al 2011), indentation (Virén et al 2018; Abellan et al 2013; Iivarinen et al 2014) and in-situ tension (Flynn et al 2011; Bhushan et al 2010). Uniaxial tension (Wahlsten et al 2019; Ní Annaidh et al 2012), biaxial tension (Tonge et al 2013) and shear experiments (Soetens et al 2018; Lamers et al 2013; Geerligs et al 2011) were performed to determine mechanical properties of skin ex vivo. Model formulations include the hyperelastic isotropic neo-Hookean

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Discussion

Conclusion