Creating bio-inspired tissue mimics of African elephant trunks' wrinkled and folded skin

Elephant trunks have been seen bulldozing trees, throwing lions several meters into the air, and picking up a tortilla chip without breaking. The skin on an elephant’s trunk is adapted to different functions on the dorsal and ventral side of the trunk much like a human hand.  We seek to understand how elephants can utilize this skin to accomplish such a wide range of tasks all while maintaining strength and flexibility. In this study, we examined the morphology and compositional differences at both the micro and macro levels of the skin down to the individual collagen fiber in the dermis. Based on the observed collagen orientation, we were able to construct knitted mimics made of yarn, an important step to creating bio-inspired and programmable tissue mimics. We use an elasticity model describing deformations of skin creases to compare the mechanical differences from the tip to the root of the trunk. Comparing the model, mimics, and elephant skin enables us to improve bio-inspired mimic designs encompassing both the morphology and composition needed for materials to be strong and flexible. This research can potentially pave the groundwork for creating programmable tissue mimics that could be used for skin graphs and other types of tissue repair engineering.