Biomechanical characterization of porcine skin under focal compressive loading with varied edge radii

There is a lack of scientific literature on the biomechanics of skin injury under focal compressive loading at various edge radii. It is understood that interactions with very small edge radii produce laceration, but as edge radii increase, the injury mechanism transitions to focal compression, and the behavior of the dermis and epidermis is not well characterized. This study quantifies effects of penetration depth and contact area of blunt, rigid hemispherical edges on loading and subsequent skin injury. A total of 172 fresh porcine skin samples were tested under normal loading using five end effectors (radii ranging from 0.2 to 2 mm) and four depths of compression (75 %, 85 %, 90 %, 95 %). Injury was defined as disruption of the epidermis and dermis exceeding 33 % of sample thickness, analyzed via digital histological methods. Results showed a clear increasing linear trend in line load (N/mm) and histological depth by radius with specimen compression. Findings suggest that tissue rupture, and thus injury, is likely a strain-based event that initiates at greater than 75 % compression. Injury was not detected at 75 % compression for any end effector but became more frequent at 85 % compression and above. No clear stratification of injury data was observed by end effector, even though local stresses increased with decreasing radius. An injury risk curve based on a Weibull fit indicates that a line load of 72 N/mm yields a 5 % risk of injury, while a line load of 200 N/mm results in a 50 % risk of injury under focal compressive loading.