The snapping shrimp dactyl plunger: a thermomechanical damage-tolerant sandwich composite

• Published in: Zoology (Jena) 2018-02, Vol.126, p.1-10
• Main Authors: Alam, Parvez, Sanka, Immanuel, Alam, Lilja Piuli, Wijaya, Saka, Sintya, Erly, Handayani, Niken Satuti Nur, Rivero-Müller, Adolfo
• Format: Article
• Language: English
• Subjects: Bio-architecture; Biomimetics; Dactyl plunger; Sandwich composite; Snapping shrimp
• ISSN: 0944-2006; 1873-2720; 1873-2720
• DOI: 10.1016/j.zool.2017.11.001

[Display omitted] •Snapping shrimps were found to have highly pressurised dactyl plungers with sandwich composite cross-sections.•The composite is structured with hard outer layers and a ca. 50% porous, chitin middle layer.•Finite element models reveal that the middle layer is able to insulate against heat and absorb mechanical energy.•Plungers are subjected to high pressures/heat and the dactyl plunger exhibits a design with thermomechanical damage tolerance. The dactyl plunger of Alpheus sp. was found to be a layered composite, with mineral-rich outer and inner layers and a chitin-rich middle layer of high porosity. The chitin-rich middle layer is itself composed of several porous chitin laminae. Modelling heat conduction through the plunger cross-section revealed that the chitin-rich layer is able to insulate heat and retard its progress through the material. Heat accumulates in the plunger after a series of successive snaps and as such, its thermally resistant design can be considered most useful under the conditions of successive snapping. The plunger has a concurrent mechanical damage-tolerant design with biogenic mineral layers, viscous (chitin–mineral) interfaces, energy-dissipating porous chitin, and sidewalls composed of ordered, layered aragonite. The snapping shrimp plunger has a design that may protect it and internal soft tissues from thermomechanical damage during plunger–socket compression prior to cavitation bubble release.