Cardiff University, School of Engineering, Cardiff CF24 3AA, United Kingdom.
J Mech Behav Biomed Mater. 2013 Feb;18:167-80. doi: 10.1016/j.jmbbm.2012.10.021. Epub 2012 Nov 19.
The mechanical characteristics of skin are extremely complex and have not been satisfactorily simulated by conventional engineering models. The ability to predict human skin behaviour and to evaluate changes in the mechanical properties of the tissue would inform engineering design and would prove valuable in a diversity of disciplines, for example the pharmaceutical and cosmetic industries, which currently rely upon experiments performed in animal models. The aim of this study was to develop a predictive anisotropic, hyperelastic constitutive model of human skin and to validate this model using laboratory data. As a corollary, the mechanical characteristics of human and murine skin have been compared. A novel experimental design, using tensile tests on circular skin specimens, and an optimisation procedure were adopted for laboratory experiments to identify the material parameters of the tissue. Uniaxial tensile tests were performed along three load axes on excised murine and human skin samples, using a single set of material parameters for each skin sample. A finite element model was developed using the transversely isotropic, hyperelastic constitutive model of Weiss et al. (1996) and was embedded within a Veronda-Westmann isotropic material matrix, using three fibre families to create anisotropic behaviour. The model was able to represent the nonlinear, anisotropic behaviour of the skin well. Additionally, examination of the optimal material coefficients and the experimental data permitted quantification of the mechanical differences between human and murine skin. Differences between the skin types, most notably the extension of the skin at low load, have highlighted some of the limitations of murine skin as a biomechanical model of the human tissue. The development of accurate, predictive computational models of human tissue, such as skin, to reduce, refine or replace animal models and to inform developments in the medical, engineering and cosmetic fields, is a significant challenge but is highly desirable. Concurrent advances in computer technology and our understanding of human physiology must be utilised to produce more accurate and accessible predictive models, such as the finite element model described in this study.
皮肤的力学特性极其复杂，传统的工程模型无法对其进行令人满意的模拟。预测人体皮肤行为并评估组织力学性能变化的能力将为工程设计提供信息，并在多个领域（例如制药和化妆品行业）具有重要价值，因为这些领域目前依赖于在动物模型上进行的实验。本研究的目的是开发一种预测各向异性的、超弹性的人体皮肤本构模型，并使用实验室数据对该模型进行验证。作为推论，比较了人体和鼠类皮肤的力学特性。采用圆形皮肤标本拉伸试验的新颖实验设计和优化程序，用于实验室实验以确定组织的材料参数。在从三个加载轴进行的单轴拉伸试验中，对离体的鼠类和人类皮肤样本进行了拉伸试验，每个皮肤样本使用一组材料参数。使用 Weiss 等人（1996 年）的横向各向同性、超弹性本构模型开发了一个有限元模型，并将其嵌入到一个 Veronda-Westmann 各向同性材料矩阵中，使用三个纤维族来创建各向异性行为。该模型能够很好地表示皮肤的非线性、各向异性行为。此外，对最优材料系数和实验数据的检查允许量化人类皮肤和鼠类皮肤之间的力学差异。皮肤类型之间的差异，尤其是在低负荷下皮肤的延伸，突出了鼠类皮肤作为人体组织生物力学模型的一些局限性。开发准确的、预测性的人体组织（如皮肤）计算模型，以减少、改进或替代动物模型，并为医学、工程和美容领域的发展提供信息，是一个重大挑战，但也是非常可取的。必须利用计算机技术和我们对人体生理学的理解的同步进展，以产生更准确和易于使用的预测模型，例如本研究中描述的有限元模型。
