Phase change material-enhanced shoe sole for foot sole thermal regulation to prevent hyperthermia

Along with the aesthetics and comfort of the shoes, the thermal characteristics of the shoes are one of the most important factors that should be considered in their design. In weight-bearing activities of daily living, the foot plantar temperature can increase considerably which can be uncomfortable and lead to injuries. Most literature has focused on the mechanical behavior of the shoe sole to accommodate cushioning. In this study, a shoe sole design that can accommodate appropriate thermal properties to prevent excessive foot temperature rise during activities of daily living was investigated. As it is challenging to find a material that has both suitable thermal and mechanical properties, in this study, a Phase Change Material (PCM) -enhanced shoe sole was innovated and proposed. In this design, a structured porous layer is embedded inside the shoe sole, in which the pore space is filled with PCM. Different low-temperature PCMs were proposed and simulated. Among them, paraffin wax (RT35) and PEG 900 showed outstanding performance. It was shown that using these PCM-enhanced shoe soles can keep foot soles cool, after 30 minutes of slow walking. These sole designs were also effective in keeping the foot sole cool during intensive activities like jogging or running