Hassan Zahouani
Professor, Ecole Centrale de Lyon
LTDS
Biography
Hassan Zahouani is a professor at École Centrale de Lyon (classes of excellence 1 and 2). He is also a lecturer at Halmstad University. His research focuses on the morphological and mechanical properties of living tissues and their evolution during aging.
For several years, Stanford University has published an international ranking of the world's top-performing scientists. Hassan Zahouani was ranked by this organization in 2021, 2022, 2023, 2024, and 2025, placing him among the top 2% of researchers. In 2024, he was cited as a Top Scholar among the top 0.5% of scientists worldwide by Scholar GPS.
Conference
Day 2
Session 3: Hydration evaluation, what's new?
Effect of hydration on the mechanical properties of the sub-skin layers
Water is the main component of our body, representing on average 70% of its total mass. This mass is 75% in infants and 65% in adults and can drop to 45% depending on body type and age. Most of this water, nearly 55%, is stored within our cells, which explains why dermatologists pinch the skin to assess its level of dehydration. Water is present throughout the skin, and its protection from external aggressors varies depending on the effectiveness of its barrier function.
This work investigates the effect of hydration on the viscoelastic behavior of the skin sublayers. Two approaches will be presented: the first method is based on the analysis of the indentation curve of a sphere under low load. The experimental model allows for the quantification of contact pressure across all skin sublayers, from the surface of the stratum corneum, by determining the elastic modulus of the epidermis, the superficial dermis, and the dermo-epidermal junction. The second approach involves non-contact loading based on the initiation of shear waves after impact by an airflow. Measuring the shear rates, elasticity, and viscosity across all layers allows for the quantification of the kinetics of hydration in the short and long term.