Auxetic incisions with alternating slit shapes: a promising technique for enhancing synthetic skin grafts expansion

Abstract

Split thickness skin grafts are widely used in treating burn injuries. To date, with limited availability of donor skin and minimal expansions offered by conventional skin grafting, it is challenging to cover large and severe burns. In this study, novel synthetic skin grafts with alternating slit (AS) shaped cut patterns were developed and tested to evaluate the expansion potentials offered by auxetic or negative Poisson’s ratio structures in skin grafting. A range of auxetic incision patterns were designed with varying unit cell dimensions, and these were projected onto skin using 3D printing. The mechanical properties and digital image correlation of the created synthetic skin grafts were used to determine stress, effective Poisson's ratio, meshing ratio (MR), and generated strains for strain loadings of up to 150%. The AS graft simulant with equal slit lengths and low slit spacings exhibited the maximum negative Poisson’s effect, expansion, and MR. Expansions were inversely related with the spacing between slits. The lowest value for the MR and highest stress was observed with high spacing, high horizontal slit length, and low vertical slit length. The expansions were highly sensitive to the applied strain, with low strains exhibiting high auxeticity. Such an extensive experimental investigation of the expansion potentials and stress estimations of skin grafts with varying AS dimensional parameters have not been conducted previously. The findings would be crucial for advancing research on mitigation of large burn injuries using high expansion skin grafts.