Entangled Elephant Skin Allows Strength and Flexibility

Materials often come with trade-offs. With great strength often comes little flexibility or stretchability. However, biological systems can frequently find unique ways to bypass these common trade-offs. Elephant trunks have near-infinite degrees of freedom, using their trunks to stretch to forage for up to 16 hours a day, consuming over 200 kg of food daily.

This is matched by their skin needing this stretchable trunk protection from the elements and environment. The skin surrounding the trunk appears to have conquered these common material trade-offs as it can allow the trunk rapid extension while providing a protective armor layer, and this paper investigates what mechanisms will enable the skin to achieve such a complex duality of strength and stretch.
We investigated the trunk and found that the skin was covered in a thick armored layer thicker than an armadillo shell. Through stained images of elephant skin, we found that the outer layer of the skin, known as the stratum corneum, can be over 2 mm thick, which is 100 times the thickness of the human abdomen stratum corneum.

This thick armored layer protects the soft layers underneath, including the tens of thousands of muscle fibers. However, the stratum corneum is just one of the many layers of skin. Deeper beneath the stratum corneum are the layers of a more flexible building block, collagen, which provides rigidity, flexibility, and strength to our skin, muscles, tendons, and more.

The functional ability of each of these structures is determined by how the collagen is arranged. Different directions of collagen produce different structures. If you look at the back of your hand, your skin can stretch from collagen-oriented parallel to the outside of the skin, providing flexibility. If you look at the palm of your hand, your skin stretches less but provides more resistance to forces you encounter daily. This is from the palm's collagen being oriented perpendicular. Throughout the body our collagen has different modes that allow different functions, however, the elephant has developed skin that has a unique feature that allows strength and flexibility, they have fibers that are tangled up like a web.
.png)
Using an advanced microscopy method known as second harmonic generation, we can vibrate the collagen, allowing us to study this web to find that elephant collagen also interacts between the collagen fibers, providing entanglement that could help contribute to the stiffening of the skin. Overall, this thick armor plus entangled collagen provide elephants with unique skin covering their trunk, allowing their flexible kevlar-like skin to provide strength while stretching. This phenomenon of entangled collagen in the skin is unique in the elephant. It could inspire the creation of new and novel materials that can avoid trade-offs by leveraging functional intelligence in robotics or even creating artificial tissues for human health.
Follow the Topic
-
Communications Biology
An open access journal from Nature Portfolio publishing high-quality research, reviews and commentary in all areas of the biological sciences, representing significant advances and bringing new biological insight to a specialized area of research.
Related Collections
With collections, you can get published faster and increase your visibility.
Brain and Body Communication in Health and Disease
Publishing Model: Open Access
Deadline: Apr 30, 2025
RNA modifications
Publishing Model: Open Access
Deadline: Apr 30, 2025
Please sign in or register for FREE
If you are a registered user on Research Communities by Springer Nature, please sign in