Expansion potential of skin grafts with novel rotating-triangle-shaped auxetic incisions

Millions of burn injuries are reported every year, with severe cases needing skin graft implantation. To date, the highest achievable expansion produced by split-thickness skin grafting has been reported to be just three times, which is insufficient for covering large burn sites with limited donor site skin. In this work, the authors studied the expansion potential of skin grafts with rotating-triangle (RT)-shaped auxetic incision patterns, which are known to exhibit a highly negative Poisson’s effect. Ten two-layer skin graft models with RT angles varying from 0 to 135° were developed and tested under uniaxial and biaxial tensile loads. Poisson’s effect, meshing ratios (MRs) and induced stresses were quantified across all models and loads up to the ultimate tensile stress. Very high expansions (MR > 45), varying widely across uniaxial and biaxial loads and without rupture, were observed for low RT angles. However, for RT angles greater than 45°, the expansions significantly decreased, with the lowest MR reported at 135°. Beyond an RT angle of 90°, the induced stresses were very high, with potential for skin rupture. Such expansion potentials and stress estimations with skin grafts have not been reported previously and would be indispensable for initiating groundbreaking advances in burn surgery research.