Development of novel hierarchical designs for skin graft simulants with high expansion potential

Abstract

Skin graft designs play an essential role in healing severe burn injuries. Split-thickness skin grafting (STSG) is one of the commonly used techniques for treating large burn injuries. In STSG, parallel cuts are projected onto a small portion of excised healthy skin for expansion and covering a larger burn area. To date, expansions reported for STSG are very low and insufficient to cover large burn areas. In this work, novel traditional and auxetic hierarchical cuts were designed on skin graft simulants, which were mechanically tested to study their expansion potential. Additive manufacturing and a two-part polymeric material were employed to fabricate the skin graft simulants. The nonlinear mechanical behavior of the hierarchical skin graft simulants was characterized using hyperelastic models. The effective Poisson's ratio, meshing ratios, and induced stresses in first and second-order hierarchical cut patterns were estimated across all skin graft simulants for up to 300% strain. Also, Statistical analysis was performed to calculate the significance among the groups. From the analysis, the skin graft simulants with second-order auxetic incision patterns were found to exhibit the lowest induced stresses and maximum expansion of approximately four times, at 300% strain. To date, traditional skin grafts have only been able to achieve up to three times expansion. Therefore, the expansions realized with the novel hierarchical skin graft simulants is unprecedented, with the potential to generate ground-breaking advances in burn injury treatment.

Finite Element Analysis of Hierarchical Metamaterial-Based Patterns for Generating High Expansion in Skin Grafting

“…In another work, Han et al [12] studied the stretchability using conductorbased silver composite auxetic structures. Several other studies also showed that the hierarchical structures can generate very high expansions [21,22,[36][37][38]. Here, six different skin graft structures were designed on the two-layer skin graft with a length and width of 35 mm.…”

“…Here, six different skin graft structures were designed on the two-layer skin graft with a length and width of 35 mm. The dimensions of the designs were taken from the literature on hierarchical architectures which shows high expansions [21,22]. The selection of the specific length was based upon the ratios taken from the slit length and slit thickness.…”

“…Hierarchical metamaterial refers to an engineered material with a hierarchical or multi-scale structure, composed of multiple levels of organization or arrangement [22,23]. This term refers to materials that are designed to exhibit distinct and enhanced properties by optimizing the interactions and arrangements of their constituent elements at various length scales.…”