The skin, being a multi-layered material, is responsible for protecting the human body from the mechanical, bacterial, and viral insults. The skin tissue may display different mechanical properties according to the anatomical locations of a body. However, these mechanical properties in different anatomical regions and at different loading directions (axial and circumferential) of the mice body to date have not been determined. In this study, the axial and circumferential loads were imposed on the mice skin samples. The elastic modulus and maximum stress of the skin tissues were measured before the failure occurred. The nonlinear mechanical behavior of the skin tissues was also computationally investigated through a suitable constitutive equation. Hyperelastic material model was calibrated using the experimental data. Regardless of the anatomic locations of the mice body, the results revealed significantly different mechanical properties in the axial and circumferential directions and, consequently, the mice skin tissue behaves like a pure anisotropic material. The highest elastic modulus was observed in the back skin under the circumferential direction (6.67 MPa), while the lowest one was seen in the abdomen skin under circumferential loading (0.80 MPa). The Ogden material model was narrowly captured the nonlinear mechanical response of the skin at different loading directions. The results help to understand the isotropic/anisotropic mechanical behavior of the skin tissue at different anatomical locations. They also have implications for a diversity of disciplines, i.e., dermatology, cosmetics industry, clinical decision making, and clinical intervention.

Skin as an external membrane has a key asset in the human body, i.e. heat balance and protection from the peripheral mechanical loads. The mechanical properties of the skin tissue are almost intricate under various loading conditions that may also differ according to the anatomical locations of a body. Although the mechanical properties of the skin tissue have been largely studied using different testing methods as well as different material models, the time-dependent viscoelastic mechanical behavior of the skin in different anatomical regions has not been quantified via the Quasilinear viscoelastic model. In this study, the quasi-linear viscoelastic mechanical properties of the rat back and abdomen skins were computed under uniaxial loading. The relaxation test was carried out on the back and abdomen of eight rats and afterward the quasi-linear viscoelastic coefficients were calculated by fitting the quasi-linear viscoelastic model to the experimental stress-relaxation data. The results revealed that the peak stress in the abdomen skin samples is slightly higher than that of the back ones. Besides, the stress reached to a balance in 100 s for both the back and abdomen skin tissues in tension. The findings of this study may have implications not only for understanding the viscoelastic timedependent mechanical behavior of the back and abdomen skin tissues but also to give a biomechanical awareness in a variety of areas such as tissue engineering, dermatology, and cosmetics industry.

Skin tissue is not only responsible for thermoregulation but also for protecting the human body from mechanical, bacterial, and viral insults. The mechanical properties of skin tissue may vary according to the anatomical locations in the body. However, the linear elastic and nonlinear hyperelastic mechanical properties of the skin in different anatomical regions and at different loading directions (axial and circumferential) so far have not been determined. In this study, the mechanical properties during tension of the rat abdomen and back were calculated at different loading directions using linear elastic and nonlinear hyperelastic material models. The skin samples were subjected to a series of tensile tests. The elastic modulus and maximum stress of the skin tissues were measured before the incidence of failure. The nonlinear mechanical behavior of the skin tissues was also computationally investigated through a constitutive equation. Hyperelastic strain energy density function was calibrated using the experimental data. The results revealed the anisotropic mechanical behavior of the abdomen and the isotropic mechanical response of the back skin. The highest elastic modulus was observed in the abdomen skin under the axial direction (10 MPa), while the lowest one was seen in the back skin under axial loading (5 MPa). The Mooney-Rivlin material model closely addressed the nonlinear mechanical behavior of the skin at different loading directions, which can be implemented in the future biomechanical models of skin tissue. The results might have implications not only for understanding of the isotropic and anisotropic mechanical behavior of skin tissue at different anatomical locations but also for providing more information for a diversity of disciplines, including dermatology, cosmetics industry, clinical decision making, and clinical intervention.