Elucidating the Mechanistic Process of Age-Induced Human Skin Wrinkling

This study provides one of the first comprehensive experimental investigations into how age-dependent mechanical changes in full-thickness human skin drive wrinkle formation under physiologically relevant tensile loads. Human skin samples spanning ages 16–91 years were excised relative to the dominant collagen fiber orientation and loaded uniaxially in directions both parallel and perpendicular to this orientation. Stress–strain curves revealed age-related increases in transverse compressive strains (−γyy) during axial loading, leading to markedly elevated Poisson’s ratios, frequently exceeding ν > 0.5 (pages 6–7). These high Poisson’s ratios were experimentally confirmed to correspond to poroelastic volume loss, verified through density measurements (page 7; Fig. 5). Wrinkle formation was imaged and quantified using silicone-elastomer negative molds and high-resolution microscopy (pages 4–5; Fig. 3). Older skin consistently produced deeper, wider, and less tortuous wrinkles regardless of collagen orientation (page 8; Fig. 6). The findings demonstrate that age-associated dermal structural degradation increases transverse contractility during tensile loading, providing a mechanistic explanation for why wrinkles deepen and align with collagen fibers as skin ages.