The Stratum Corneum (SC) is the outermost layer of the human skin that essentially provides mechanical protection and a controlled barrier to the external environment. A.

s a result, the SC is in constant interaction with the outside environment and contributes immensely towards appearance, texture and feel of the skin. Recent studies have shown that the SC mechanical properties alter the biomechanical response of aging skin and also impact the stress state of the underlying tissue. Therefore, knowledge of the mechanical behavior of the SC is very important for clinical and cosmetic research, such as the development of personal care products and the understanding of skin abnormalities. As the SC has a complex hierarchical structure, it is essential to understand its behavior at different length scales, for a good understanding of the overall mechanical behavior of the SC. Currently most of the available in-silico mechanical models of skin define the SC at the tissue level. A cellular scale numerical model would help us understand the biomechanical and clinical implications of changes in the SC microstructure on its mechanical properties. Therefore, The aim of this thesis is to propose a multiscale computational framework that can quantify the mechanical behavior of the SC at tissue level with respect to the changes in its cellular microstructure. As the SC can be treated as a natural composite material, micromechanics provides us with the tools for analyzing its mechanical behavior.

The cellular scale unit cell is defined in terms of three main mechanical components of the SC, namely corneocytes, lipids and corneodesmosomes. Input parameters for the model are obtained from the in-vitro morphological and mechanical data available in literature. Finite element simulations are carried out for different load cases in order to calculate the overall properties of the SC from the cellular scale unit cell. From the mechanics point of view, in order to understand the scale and boundary conditions effects on the SC moduli, the model response to uniform displacement, uniform traction and periodic boundary conditions is studied. The parametric studies using periodic boundary conditions on the unit cell reveal corneodesmosomes to be an efficient target to effectively reduce the SC modulus. Within the framework of the proposed model, the results also point to morphological and mechanical changes in the inter-cellular space to be the major cause for changing the SC Young's modulus with relative humidity.