Modelling the structure and mechanical properties of skin

Abstract

The mechanical properties of skin are primarily determined by the structure and properties of individual components within the dermis. In order to understand and to quantify the relationship between microstructure and mechanical function of skin, a structure-based biomechanical model of skin was developed. Firstly, an imaging study was performed to extract quantitative data on collagen fibre orientation. Based on observations from confocal laser scanning microscopy (CLSM) images, a conceptual model, expressed in terms of a density distribution function to describe collagen orientation, was proposed. It was demonstrated that two parameters of this distribution may be directly determined using CLSM image analysis. An important advantage of this approach is that model parameters can be estimated directly from observable microstructural features. To characterise the mechanical response of skin, multiaxial tensile experiments were performed on porcine skin in vitro. Displacement fields at each deformation step were determined using a cross-correlation technique. A modelling framework was developed to simulate the experiments, whereby measured forces were applied to finite element models that were created to represent the geometries of the tissue samples. Parameters of the chosen structure-based constitutive relation were identified using nonlinear optimisation. The imaging techniques, experimental set-up and development of the biomechanical skin model have contributed to increased understanding of the in-plane, anisotropic, nonlinear, mechanical behaviour of skin.