Textured fluorapatite bonded to calcium sulphate strengthen stomatopod raptorial appendages.
Stomatopods are shallow-water crustaceans that employ powerful dactyl appendages to hunt their prey. Deployed at high velocities, these hammer-like clubs or spear-like devices are able to inflict substantial impact forces. Here we demonstrate that dactyl impact surfaces consist of a finely-tuned mineral gradient, with fluorapatite substituting amorphous apatite towards the outer surface. Raman spectroscopy measurements show that calcium sulphate, previously not reported in mechanically active biotools, is co-localized with fluorapatite. Ab initio computations suggest that fluorapatite/calcium sulphate interfaces provide binding stability and promote the disordered-to-ordered transition of fluorapatite. Nanomechanical measurements show that fluorapatite crystalline orientation correlates with an anisotropic stiffness response and indicate significant differences in the fracture tolerance between the two types of appendages. Our findings shed new light on the crystallochemical and microstructural strategies allowing these intriguing biotools to optimize impact forces, providing physicochemical information that could be translated towards the synthesis of impact-resistant functional materials and coatings.
School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Shahrouz
S
Amini
Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Potsdam-Golm, 14424 Potsdam, Germany.
Admir
A
Masic
Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Potsdam-Golm, 14424 Potsdam, Germany.
Luca
L
Bertinetti
School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.
Jefri Sanusi
JS
Teguh
School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Jason S
JS
Herrin
School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Xi
X
Zhu
School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Haibin
H
Su
1] School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore [2] School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
Ali
A
Miserez
D000818:Animals; D001031:Apatites / Q000737:chemistry*; D002133:Calcium Sulfate / Q000737:chemistry*; D003445:Crustacea / Q000033:anatomy & histology*; D008855:Microscopy, Electron, Scanning; D013057:Spectrum Analysis
D001031:Apatites; C025105:fluorapatite; D002133:Calcium Sulfate