DTA

Dottorato

KAMARE, BEHNAM

bkamareh@gmail.com

etd-06062024-185246

Biomechanical analysis of elephant trunk skin for future adaptive artificial skins

ING-INF/06

Istituto di Biorobotica - PHD IN BIOROBOTICA

relatore Dott.ssa BECCAI, LUCIA
Presidente Prof. CIANCHETTI, MATTEO

• Elephant
• trunk skin
• Skin microstructure
• Skin Morphology
• Skin Biomechanics

15/11/2024;

parziale

The Asian elephant trunk exhibits remarkable multifunctionality crucial for its survival, relying on adaptability to its environment and exceptional dexterity. This study employs a comprehensive approach to investigate the trunk's skin, aiming to understand its simultaneous flexibility, toughness, and sensitivity. The skin is examined through optical microscopy, histological analysis, sheet plastination, and second harmonic generation (SHG) microscopy, which unveils the skin's structure and sheds light on its ability to withstand high forces while remaining flexible. For the first time, the reticular arrangement of collagen fibers in elephant skin is detected by optical microscopy and the effect of fibers arrangement on improving the deformability of skin is explained. The movements of fibers during skin elongation are detected and analyzed to explain the mechanical behavior of the skin. Proximal, medial, and distal regions are analyzed through uniaxial and indentation experiments. An in-depth analysis is performed on cyclic uniaxial tests and investigates stiffening and plastic deformation during cyclic tests. Other features like rate dependency, relaxation, and skin recovery are investigated as well. The inverse finite method is used to retrieve the mechanical properties of the skin layers and collagen fibers. A mock-up of skin, composed of artificial fibers embedded in a soft matrix material, is utilized to simulate and understand the mechanical behavior of natural skin observed during mechanical tests. Finite element analysis explores the impact of the epidermis' discrete island-like morphology and wrinkles on skin stretchability. The simulations show the focalizing effect of internal 3D dermal ridges and papillae on stress/strain concentration in specific regions. Observations of mechanoreceptors in different depths of the skin, especially in dermal papillae, give a clue for understanding the role of skin microstructure in the sensitivity of skin. The observed differences of microstructure and morphology between dorsal and ventral skin are as significant as if we are facing two different organs and these differences can be attributed to the different functionalities of the trunk regions. These findings deepen our understanding of the Asian elephant trunk and offer insights for designing resilient, deformable, and sensitive artificial skins.

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