Chapter 3 Skin Biothermomechanics

The development and widespread use of thermal therapies for skin diseases and injuries with advances in laser, microwave, and similar technologies have not been built upon the detailed understanding of the biothermomechanical–neurophysiological behavior of skin tissue. The emerging studies on skin biothermomechanics are therefore important for it attempts to understand macroscale tissue response to heat-induced microstructural transformations. Skin biothermomechanics is highly interdisciplinary, involving bioheat transfer, burn damage, biomechanics, and physiology. This chapter presents firstly the various theoretical approaches for determining the thermal, thermomechanical, and thermal pain response in skin tissue induced by transient heating. Given the complicated microstructure of skin tissue and its relatively lengthy thermal relaxation time, both Fourier and non-Fourier bioheat transfer models are employed. While insightful, the predictive capability of the current theoretical modeling is, nonetheless, limited by the comparatively few relative experimental studies on temperature-dependent properties of the skin tissue. To better understand the variation in skin properties with temperature and the corresponding collagen denaturation, focus is then placed upon the experimental characterization of the thermomechanical behavior of skin tissue. Uniaxial and biaxial hydrothermal tensile testing systems as well as hydrothermal compressive testing system are purposely designed and built which, together with a commercially available dynamic mechanical analyzer, are employed to obtain suitable data to quantify the influence of temperature and the corresponding thermal damage on the mechanical performance of skin tissue, including tensile, compressive, and viscoelastic behaviors.