Unique morphology and mechanical property of Chinese sturgeon (Acipenser sinensis) fish skin

Abstract

Chinese sturgeon (Acipenser sinensis) fish skin is an excellent natural material with remarkable mechanical properties owing to the unique structures of the helical stacking fibres. In this work, the authors studied the potential role of the sturgeon fish skin in the protective function through testing and analysed the structural features and mechanical properties of the stratum compactum in the fish skin. Scanning electron microscopy images of the sturgeon fish skin revealed that the skin was primarily composed of the stratum compactum. The stratum compactum was characterised by the helically arranged fibre structures and the helical-ply angle decreased from the anterior region of the fish body to the posterior region. Mechanical tests containing tension and penetration experiments demonstrated that the stratum compactum provided the sturgeon fish skin the capability to effectively resist bite and laceration by predators. Furthermore, the experimental results also confirmed that the sturgeon fish skin showed two distinct mechanisms against tension and penetration. These findings may provide a novel biomimetic design template for both flexible and tough body armour.

Characterization of the structural and mechanical properties of pinecone fish (Monocentris japonica) scales

“…Obviously, the collagen fibers in a single ply are not arranged unidirectionally, but present a feather‐like distribution (Figure 6c), which is distinctly different from the collagen layers of other teleost fish scales, such as Arapaima gigas (Torres et al, 2008), Strip bass (Zhu et al, 2012), Megalops atlanticus (Murcia et al, 2017), and Cyprinus carpio (Garrano et al, 2012), where the collagen fibers are oriented in one direction for each individual ply. In addition, the collagen fibers are not straight but slightly curved, which can increase the strain of fibrous layers when subjected to tensile forces (Zheng et al, 2020). Also worth noting is that there is a fiber orientation angle of 60° between two adjacent collagen plies (Figure 6d).…”

“…The highly mineralized structure of the outer bone layer has a positive effect on increasing the penetration resistance, and the pore structures in the intermediate bone layer also contribute to absorbing high compression energy (Zheng et al, 2019). Meanwhile, the feather‐like stacking collagen fibers in the inner layer help to deflect and impede the propagation of crack, and further increase the force required to completely penetrate the scales (Figure 12) (Zheng et al, 2020). The penetration force value of M. japonica scales in this paper is much higher than that of Chinese sturgeon (about 27.33 N), Grass carp (about 14 N), Parabramis pekinensis (about 13.3 N), Striped bass (about 12.25 N), and Carassius auratus (about 11 N) (Fang et al, 2014; Zheng et al, 2020; Zhu et al, 2013).…”

Superior Damage Tolerance of Fish Skins

“…How collagen microfibers in skin rearrange at high strains, and these rearrangement leads to superior mechanical properties and damage tolerance, have been previously unexplored. It is well characterized that the mechanical properties of fish skins are location dependent, as experimentally observed for tensile stress-strain curves of striped bass skin [5] and Chinese sturgeon skin [14]. However, our study here focuses on the damage tolerance mechanism of the skin in general, not on specific locations.…”

Morphology and mechanical performance between the skin surface ofRana dybowskiiandBufo gargarizans

“…These remarkable properties of skin make it a promising biological material [12, 13]. For instance, the skin from some fish species( Arapaima gigas and Acipenser sinensis ) are now receiving attention due to its toughness and puncture resistance, which can provide a design template for lightweight and high‐strength body armour [14, 15]. Besides, the skin of sharks exhibits riblet structures aligned in the direction of flow which are known to reduce skin friction drag in the turbulent‐flow regime, and the riblet surfaces inspired by shark skin have been widely used in engineering [16, 17].…”

“…puncture resistance, which can provide a design template for lightweight and high-strength body armour [14,15]. Besides, the skin of sharks exhibits riblet structures aligned in the direction of flow which are known to reduce skin friction drag in the turbulent-flow regime, and the riblet surfaces inspired by shark skin have been widely used in engineering [16,17].…”