Abstract Skin is the outermost layer of the body and acts as a primary protective barrier against external agents such as heat, light, infection, and injury. Additionally, skin regulates the temperature of the body and the exchange of fluids. Skin contains a vast network of nerves, glands, and vessels that enable sensing of heat, touch, pressure and pain, and is also a crucial interface that regulates our body temperature and stores water and lipids to maintain a healthy metabolism. In order to fulfill such a broad range of functions throughout life, skin must be able to withstand and recover from significant deformation as well as mitigate tear propagation that can occur during growth, movement, and injuries affecting its integrity. Hence, characterizing the mechanical behavior of skin and understanding the underlying mechanisms of deformation at different spatial scales is essential in a large spectrum of applications such as surgery, cosmetics, forensics, biomimetics and engineering of protective gear or artificial grafts, among others. The present review draws a comprehensive list of experimental techniques that have been developed over the years to test skin’s nonlinear elastic, viscoelastic, and dissipative properties. To identify parameters affecting its behavior, a significant number of models have been developed, some of which are detailed here; they range from macroscopic constitutive laws to structurally-based formulations, involving nonlinear, dynamic, or damage-inducing processes. The principal structural elements within the dermis, and especially the arrangement and orientation of the collagen fibrils and fibers, are presented; their incorporation into the constitutive models is discussed. Future challenges and perspectives in implementing more accurate structural models are highlighted. Major efforts at developing and using synthetic skin are described.

中文翻译：

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皮肤材料科学：分析、表征和建模

摘要 皮肤是身体的最外层，是抵御外部因素（如热、光、感染和伤害）的主要保护屏障。此外，皮肤调节身体的温度和液体的交换。皮肤包含庞大的神经、腺体和血管网络，可以感知热量、触觉、压力和疼痛，同时也是调节体温和储存水分和脂质以维持健康新陈代谢的重要界面。为了在整个生命过程中实现如此广泛的功能，皮肤必须能够承受显着变形并从中恢复，并减轻在生长、运动和损伤过程中可能发生的撕裂传播，影响其完整性。因此，表征皮肤的机械行为并了解不同空间尺度下变形的潜在机制对于手术、化妆品、法医、仿生学和防护装备或人工移植物工程等广泛应用至关重要。本综述列出了多年来为测试皮肤的非线性弹性、粘弹性和耗散特性而开发的一系列实验技术。为了确定影响其行为的参数，已经开发了大量模型，此处详细介绍了其中的一些模型；它们的范围从宏观本构定律到基于结构的公式，涉及非线性、动态或损伤诱导过程。真皮内的主要结构元素，尤其是胶原原纤维和纤维的排列和方向；讨论了它们与本构模型的结合。强调了在实施更准确的结构模型方面的未来挑战和前景。描述了开发和使用合成皮肤的主要努力。