Material properties of the skin of the Kenyan sand boa Gongylophis colubrinus (Squamata, Boidae)

Klein, Marie-Christin G.; Deuschle, Julia; Gorb, Stanislav N.

doi:10.1007/s00359-010-0556-y

Cited by 76 publications

(68 citation statements)

References 39 publications

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“…Pure bulk materials are almost absent in biological structures where proper combinations of different constituents often lead to mechanical gradients with important functional significances. This has, for example, been shown for insect cuticle 17 , snake skin 18 and human teeth 19,20 .…”

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confidence: 67%

Evidence for a material gradient in the adhesive tarsal setae of the ladybird beetle Coccinella septempunctata

2013

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For an insect to be able to efficiently attach to surfaces, the adhesive pads on the distal parts of its legs must establish large contact areas. In case of hairy adhesive pads this requires flexibility of the contact-forming bristles, called adhesive tarsal setae. However, too flexible setae would have a low mechanical stability resulting in a decreased attachment ability of the pads. Here we show that the adhesive tarsal setae of the ladybird beetle Coccinella septempunctata feature pronounced gradients in the material composition and properties along their length. The Young's modulus ranges from 1.2 MPa at the tips, where we found the incorporation of high proportions of the elastic protein resilin, to 6.8 GPa at the bases of the setae. These gradients likely represent an evolutionary optimization, which increases the performance of the adhesive system by enabling effective adaptation to rough surfaces while simultaneously preventing lateral collapse of the setae.

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Evidence for a material gradient in the adhesive tarsal setae of the ladybird beetle Coccinella septempunctata

2013

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“…Tensile tests on skin strips (the outer from the inner layer of the dermis, 0.30 mm) from a gecko (Ailuronyx seychellensis) show a breaking stress of 0.9 MPa, an elastic modulus of 4.6 MPa and failure strain at 0.3 [278]. Mechanical studies on the epidermis shed in four snake species demonstrate that all species show a gradient in properties: the integument consists of hard, robust outer scale layers (Oberhäutchen and beta-layer) with a higher effective modulus and higher hardness, and soft, flexible inner scale layers (alpha-and clear layers) [154,279]. Fig.…”

Section: Reptilian Epidermismentioning

confidence: 99%

“…Fig. 64 shows the nanoindentation results for the outer scale layers and inner scale layers of ventral scales from Kenyan sand boa G. colubrinus [154] as a function of indentation depth. It is clear that the outer scale layers exhibit much higher values all through the load-displacement than the inner scale layers (Fig.…”

Section: Reptilian Epidermismentioning

confidence: 99%

“…There is also a difference between the hardness values of the outer (0.28 GPa) and inner (0.14 GPa) scale layers. Compared with other keratinous materials and considering the mechanical variations of a-and b-keratins, it was suggested that the b-layers' main function is to protect the epidermis against abrasion [280], and that the high abrasion resistance of snake epidermis is due to the material property gradient of the integument from a hard and inflexible outside to a soft and elastic inside [154]. For a system involving large loads under pressure against abrasion, such a design leads to more uniform stress distribution and the minimization of the probability of local stress concentration [183,281].…”

Section: Reptilian Epidermismentioning

confidence: 99%

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Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

Wang

Yang

McKittrick

et al. 2016

Progress in Materials Science

679

474

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a b s t r a c tA ubiquitous biological material, keratin represents a group of insoluble, usually high-sulfur content and filament-forming proteins, constituting the bulk of epidermal appendages such as hair, nails, claws, turtle scutes, horns, whale baleen, beaks, and feathers. These keratinous materials are formed by cells filled with keratin and are considered 'dead tissues'. Nevertheless, they are among the toughest biological materials, serving as a wide variety of interesting functions, e.g. scales to armor body, horns to combat aggressors, hagfish slime as defense against predators, nails and claws to increase prehension, hair and fur to protect against the environment. The vivid inspiring examples can offer useful solutions to design new structural and functional materials.Keratins can be classified as a-and b-types. Both show a characteristic filament-matrix structure: 7 nm diameter intermediate filaments for a-keratin, and 3 nm diameter filaments for b-keratin.Both are embedded in an amorphous keratin matrix. The molecular unit of intermediate filaments is a coiled-coil heterodimer and that of b-keratin filament is a pleated sheet. The mechanical response of a-keratin has been extensively studied and shows linear Hookean, yield and post-yield regions, and in some cases, a high reversible elastic deformation. Thus, they can be also be considered 'biopolymers'. On the other hand, b-keratin has not been investigated as comprehensively. Keratinous materials are strain-rate sensitive, and the effect of hydration is significant.Keratinous materials exhibit a complex hierarchical structure: polypeptide chains and filament-matrix structures at the nanoscale, Progress in Materials Science 76 (2016) 229-318 Contents lists available at ScienceDirect Progress in Materials Sciencej o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / p m a t s c i organization of keratinized cells into lamellar, tubular-intertubular, fiber or layered structures at the microscale, and solid, compact sheaths over porous core, sandwich or threads at the macroscale. These produce a wide range of mechanical properties: the Young's modulus ranges from 10 MPa in stratum corneum to about 2.5 GPa in feathers, and the tensile strength varies from 2 MPa in stratum corneum to 530 MPa in dry hagfish slime threads. Therefore, they are able to serve various functions including diffusion barrier, buffering external attack, energy-absorption, impact-resistance, piercing opponents, withstanding repeated stress and aerodynamic forces, and resisting buckling and penetration.A fascinating part of the new frontier of materials study is the development of bioinspired materials and designs. A comprehensive understanding of the biochemistry, structure and mechanical properties of keratins and keratinous materials is of great importance for keratin-based bioinspired materials and designs. Current bioinspired efforts including the manufacturing of quill-inspired aluminum composites, animal horn-inspired SiC composites, and feather-i...

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“…This supposes that the epidermis, especially that of the ventral body side, has to permanently endure friction forces. Because the epidermis is constantly in contact with the solid substrates, one can expect some specializations in the snake epidermis against abrasion [1]. Such specializations include layered organization of the epidermis, material properties of the epidermis and its surface microstructure.…”

Section: Introductionmentioning

confidence: 99%

Epidermis architecture and material properties of the skin of four snake species

Klein

Gorb

2012

J. R. Soc. Interface.

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107

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On the basis of structural and experimental data, it was previously demonstrated that the snake integument consists of a hard, robust, inflexible outer surface (Oberhäutchen and b-layer) and softer, flexible inner layers (a-layers). It is not clear whether this phenomenon is a general adaptation of snakes to limbless locomotion or only to specific conditions, such as habitat and locomotion. The aim of the present study was to compare the structure and material properties of the outer scale layers (OSLs) and inner scale layers (ISLs) of the exuvium epidermis in four snake species specialized to live in different habitats: Lampropeltis getula californiae (terrestrial), Epicrates cenchria cenchria (generalist), Morelia viridis (arboreal) and Gongylophis colubrinus (sand-burrowing). Scanning electron microscopy (SEM) of skin cross sections revealed a strong variation in the epidermis structure between species. The nanoindentation experiments clearly demonstrated a gradient of material properties along the epidermis in the integument of all the species studied. The presence of such a gradient is a possible adaptation to locomotion and wear minimization on natural substrates. In general, the difference in both the effective elastic modulus and hardness of the OSL and ISL between species was not large compared with the difference in epidermis thickness and architecture.

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Material properties of the skin of the Kenyan sand boa Gongylophis colubrinus (Squamata, Boidae)

Cited by 76 publications

References 39 publications

Evidence for a material gradient in the adhesive tarsal setae of the ladybird beetle Coccinella septempunctata

Evidence for a material gradient in the adhesive tarsal setae of the ladybird beetle Coccinella septempunctata

Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

Epidermis architecture and material properties of the skin of four snake species

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