Estimating material parameters of human skin in vivo

Abstract

An accurate mathematical representation of the mechanical behaviour of human skin is essential when simulating deformations occurring in the skin during body movements or clinical procedures. In this study constitutive stress-strain relationships based on experimental data from human skin in vivo were obtained. A series of multiaxial loading experiments were performed on the forearms of four age- and gender matched subjects. The tissue geometry, together with recorded displacements and boundary forces, were combined in an analysis using finite element modelling. A non-linear optimization technique was developed to estimate values for the material parameters of a previously published constitutive law, describing the stress-strain relationship as a non-linear anisotropic membrane. Ten sets of material parameters where estimated from the experiments, showing considerable differences in mechanical behaviour both between individual subjects as well as mirrored body locations on a single subject. The accuracy of applications that simulate large deformations of human skin could be improved by using the parameters found from the in vivo experiments as described in this study.

A review of tissue-engineered skin bioconstructs available for skin reconstruction

“…Such techniques include transforming the static tests into an oscillatory mode, but also by the measurement of shear wave propagation, and suction cup techniques, often with the use of ultrasound scanning to identify movements in underlying tissues. More recently, considerable progress has been made in the modelling of the viscoelastic properties of skin; for instance a model using only four parameters has been developed by Khatyr et al (2004) which describes the behaviour of skin well, and sets of important material parameters which should be considered in modelling skin have been identified by Kvistedal & Nielsen (2009). Of particular interest when considering the interface of biomaterials with native skin are the findings of Holt et al (2008) while measuring the viscoelasticity of skin under low shear and low frequency conditions.…”

Mathematical and computational modelling of skin biophysics: a review

“…As alluded to in Introduction section, the skin is a very complex biological system featuring a multitude of coupled physical processes acting in concert, or sequentially, as for instance, in the case of wound healing where a cascade of biochemical and mechanobiological events is triggered by an injury [12]. From the mechanical and material science point of view, the skin is primarily a multi-phasic and multi-scale structure which, as a result, encompasses a rich set of mechanical properties and constitutive behaviours [13,14]. The biological nature of this structure renders these properties very dynamic, particularly over a lifetime, and like most biological tissues, there is a strong variability according to body site, individuals, age, sex, ethnicity and exposure to specific environmental conditions [15,16].…”

“…uniaxial and biaxial tensile tests [34, [40][41][42], multi-axial tests [13,43], application of torsion loads [44], indentation [45], suction [39,[46][47][48][49] and bulge testing [50]. More recent techniques have focused on the experimental characterization of the mechanical properties of the epidermis [51][52][53] which are particularly relevant for cosmetic and pharmaceutical applications.…”

3D characterization of viscoelastic hydrostatic pressure field in human skin in vivo: numerical contact-free creep tests

“…Previous research has established that the human skin is a stratified medium composed of non-homogeneous, anisotropic, non-linear viscoelastic materials subject to pre-stress in vivo [17][18][19]. It is organized in four main layers which are, from the skin outer surface inwards: the stratum corneum (SC), the viable epidermis (VE), the dermis (DE) and the hypodermis (HY) [20].…”