Abstract:
Nonlinear and anisotropic mechanical behavior of skin is essential in various applications such as dermatology,
cosmetic products, forensic science, and computational studies. The present study quantifies the mechanical
anisotropy of skin using the bulge method and full-field imaging technique. In bulging, the saline solution at 37 �C mimics the in vivo body temperature and fluid conditions, and all experiments were performed in the control
environment. Assumption of thin spherical shell membrane theory and imaging techniques were implemented to
obtain the anisotropic stress strain relations. Further, stress strain relations at an interval of 10� were calculated
to obtain the variation in modulus with direction. Histological examinations were performed to signify the role of
the collagen fibers orientation on the mechanical properties. The maximum and minimum linear modulus and
collagen fiber orientation intensity were found in good agreement. The angular difference between maximum
and minimum linear modulus and orientation intensity was found 71� � 7� and 76� � 5� respectively, and the
percentage difference was 43.4 � 8.2 and 52.5 � 6.4 respectively. Further, a significant difference in the
maximum and minimum collagen orientation intensity between the untested and tested specimens indicates the
realignment of the fibers. Additionally, a cubic polynomial empirical relation was established to calculate the
quantitative variation in the apparent modulus with the directions, which serves for the anisotropic modeling of
the skin. The experimental technique used in this study can be applied for anisotropic quantification of planar
soft tissues as well as can be utilized to imitate the tissue expansion procedure used in reconstructive surgery.
