Mechanical Loading for Modifying Tissue Water Content and Optical Properties

Abstract

The majority of the physical properties of tissue depend directly on the interstitial or intracellular concentration of water within the epidermal and dermal layers. The relationship between skin constituent concentrations, such as water and protein, and the mechanical and optical properties of human skin is important to understand its complex nature. Localized mechanical loading has been proven to alter optical properties of tissue, but the mechanisms by which it is accomplished have not been studied in depth. In this thesis, skinâ s complex nature is investigated experimentally and computationally to give us better insight on how localized mechanical loading changes tissues water content and its optical properties. Load-based compression and subsequent increased optical power transmission through tissue is accomplished to explore a relationship between localized mechanical loading and tissue optical and mechanical properties. Using Optical Coherence Tomography (OCT), modification of optical properties, such as refractive index, are observed to deduce water concentration changes in tissue due to mechanical compression. A computational finite element model is developed to correlate applied mechanical force to tissue strain and water transport. Comprehensive understanding of the underlying physical principles governing the optical property changes within skin due to water concentration variation will enable future development of applications in the engineered tissue optics field.