Thermo-mechanical response of multilayer skin tissue under laser irradiation: Coupling bioheat transfer and nonlinear plate theory

This study presents a coupled thermo-mechanical model to investigate the three-dimensional response of multilayer skin tissue under flat-top laser irradiation. The Pennes bioheat transfer equation is reformulated to derive an analytical solution for the three-dimensional temperature field using the method of separation of variables combined with Newton-Cotes quadrature. Based on the temperature distribution, the Timoshenko-Mindlin plate theory is applied to construct nonlinear governing equations for transversely isotropic skin composed of the epidermis, dermis, and subcutaneous layers. The mechanical response is solved using the finite difference method and Newmark integration. Parametric studies reveal that shorter-wavelength lasers lead to greater thermal stress and deformation, while increased blood perfusion mitigates surface stress due to enhanced heat dissipation. A smaller laser spot radius results in higher stress concentrations because of increased energy density. The model’s predictions agree well with numerical simulations, confirming its capability to capture the evolution of internal stress in skin tissue under laser exposure. The analytical solution of the 3D temperature field provides a theoretical foundation for optimising laser parameters in thermal therapies.