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Structure and Mechanical Properties of Pangolin Scales as Flexible Dermal Armor Bin Wang, Wen Yang and Marc A. Meyers
Materials Science and Engineering Program, Jacobs School of Engineering, University of California, San Diego
Keratin is an important structural protein in the
protective covering of animals, and it is among the
toughest biological materials in nature. Pangolin
scales are typical keratinized materials, and they have
distinguished and effective defense to resist external
attack and pray. The knowledge of structure-property
relationship of pangolin scales to figure out how they
defense against external force will help scientists
develop new functional dermal armor materials.
Background
Function of pangolin scales as armor in real life:
http://www.animal-space.net/2010/12/lion-vs-pangolin.html
By British tour
guide Mark
Sheridan in
Tanzania
Scales organization
pangolins
Ground
(Chinese pangolins) Arboreal
(African pangolins)
(3) (2)
orientation
Internal
surface
External
surface
(1) broad
rhombic
shape
peltate
shape folding
shape
Scale morphology & structure
Three-
dimensional
optical
microscopy
Chinese pangolin African pangolin
SEM of Chinese
pangolin scale
External surface
( polished) External surface
( not polished)
Conclusions & future work
Cross-section of the scales: three-layered structure Preparation: scales were fractured, fixed in 2.5% glutaradehyde
for 3h, and then immersed in 30%, 50%, 75%, 80%, 95%, 100%
and 100% alcohol solutions, each for 15min.
Transverse
Longitudinal
Dorsal layer Intermediate layer Ventral layer
Dorsal layer Intermediate layer Ventral layer
Tensile tests
• Overlapping with each other;
• Pointing backward with sharp
tips exposed;
• Can be divided into three
groups: (1), (2), and (3);
Experiments: tensile samples were laser cut and
polished, then tested under different strain rates, at
10-2 s-1, 10-3 s-1, 10-4s-1;
Dimensions of samples: thickness: ~0.5mm, width:
~1.65mm, gauge length: ~7.5mm
African pangolin
scale sample
Chinese pangolin
scale sample
1. Protection mechanism of pangolin scales:
Macro: Overlapping→”sharp-edge” ball;
Micro: a) Scales on surface;
b) Lamellae in different orientations;
2. Property comparison:
African pangolin scale is higher than Chinese
ones;
3. Future work:
Compression, bending, nanoscrach and
nanoindentation.
50 µm 50 µm
5 µm
200 µm
10 µm 5 µm
5 µm 10 µm 5 µm
500 µm
L1
L2
L3
L1 L2 L3
T1
T2
T3
T1 T2 T3