Mechanics of Elephant Trunk Wrinkles

Elephant skin is obviously wrinkled, but no quantitative measurements have been made of why the trunk has such wrinkly skin. Through videos of trunk movement at Zoo Atlanta and dissections of a trunk from the Smithsonian Institute we report the geometry of the wrinkles and rationalize their function. Elephants can elongate their trunk by over 40%, but have little or no compression capability. Skin at the trunk’s root forms square-waved wrinkles and is twice as thick as the skin at the tip which forms sinusoidal wrinkles. We rationalize that elephants use these wrinkling properties to perform incredible bending, elongation, and strength with their trunk. The energy of wrinkling will be compared to wrinkling phenomenon in the biological world. This work will relate to biologically inspired soft robotic manipulators.