Lakhani Piyush, Dwivedi Krashn K, Kumar Navin
Department of Mechanical Engineering, Indian Institute of Technology Ropar, Rupnagar, 140001, Punjab, India.
Center for Biomedical Engineering, Indian Institute of Technology Ropar, Rupnagar, 140001, Punjab, India.
J Mech Behav Biomed Mater. 2020 Apr;104:103693. doi: 10.1016/j.jmbbm.2020.103693. Epub 2020 Feb 11.
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.
皮肤的非线性和各向异性力学行为在皮肤病学、化妆品、法医学和计算研究等各种应用中至关重要。本研究使用鼓胀法和全场成像技术对皮肤的力学各向异性进行量化。在鼓胀过程中，37°C的盐溶液模拟体内体温和流体条件，所有实验均在控制环境中进行。采用薄球壳膜理论假设和成像技术来获得各向异性应力应变关系。此外，计算了间隔10°的应力应变关系，以获得模量随方向的变化。进行组织学检查以表明胶原纤维取向对力学性能的作用。发现最大和最小线性模量与胶原纤维取向强度吻合良好。最大和最小线性模量与取向强度之间的角度差分别为71°±7°和76°±5°，百分比差分别为43.4±8.2和52.5±6.4。此外，未测试和测试样本之间最大和最小胶原取向强度的显著差异表明纤维发生了重新排列。此外，建立了一个三次多项式经验关系来计算表观模量随方向的定量变化，这用于皮肤的各向异性建模。本研究中使用的实验技术可用于平面软组织的各向异性量化，也可用于模拟重建手术中使用的组织扩张过程。
