Modeling and Mechanical Characterization of Auxetic Skin Grafts

Burn injuries commonly happen because of fire from blasts and accidents. Every year, millions of patients suffer from mild or severe degrees of burns. Full-thickness or split-thickness skin grafting (STSG) methods are used to recover the burn area from severe burn injuries. The STSG method involves creation of parallel incision patterns on the excising healthy skin. The biomedical device, a skin graft mesher, is used to project the patterns with specific lengths and spacing between alternate slits. Meshing allows the grafts to expand and cover a large burn area. However, to date, the claimed expansion area of the meshing device is much less than the realistically covered area during the skin grafting procedure. The maximum enlargement possible via skin grafting through experiments was reported to be less than three, which is insufficient to cover up large burn areas with limited amounts of donor skin. In this study, we investigated the expansion potential of skin grafts projected with novel auxetic incision designs (i.e., alternating slit (AS), I-shaped (IS), rotating triangle (RT), and I-shaped re-entrant (IRE) auxetic structures), which are known to show negative Poisson’s effect. Using four distinct auxetic incision patterns, skin graft models were designed and tested uniaxially. The induced stresses, Poisson’s ratio, and expansion ratios were estimated for all the auxetic skin graft models. Under uniaxial loading conditions, the auxetic skin graft models produced expansion potentials which were higher than conventional skin grafts. The AS graft model was found to exhibit the highest expansion ratio. These novel findings are anticipated to advance skin graft research and improve burn surgery outcomes.