Numerical and Experimental Study of the Mechanical Response of Diatom Frustules

Abstract

Diatom frustules, with their hierarchical three-dimensional patterned silica structures at nano to micrometer dimensions, can be a paragon for the design of lightweight structural materials. However, the mechanical properties of frustules, especially the species with pennate symmetry, have not been studied systematically. A novel approach combining in situ micro-indentation and high-resolution X-ray computed tomography (XCT)-based finite element analysis (FEA) at the identical sample is developed and applied to Didymosphenia geminata frustule. Furthermore, scanning electron microscopy and transmission electron microscopy investigations are conducted to obtain detailed information regarding the resolvable structures and the composition. During the in situ micro-indentation studies of Didymosphenia geminata frustule, a mainly elastic deformation behavior with displacement discontinuities/non-linearities is observed. To extract material properties from obtained load-displacement curves in the elastic region, elastic finite element method (FEM) simulations are conducted. Young’s modulus is determined as 31.8 GPa. The method described in this paper allows understanding of the mechanical behavior of very complex structures.

Didymo and Its Polysaccharide Stalks: Beneficial to the Environment or Not?

“…This group has been extensively studied by researchers since the 18th century because of its unique and complicatedly patterned frustules (silica cell walls). The mechanical structure of frustules was well investigated, revealing interesting characterizations and patterns [17][18][19]. Interestingly, the frustule is mainly composed of chitin [20] in biogenic silica, which is different than other chitin-based algae [1,21] in nature.…”

“…Interestingly, the frustule is mainly composed of chitin [20] in biogenic silica, which is different than other chitin-based algae [1,21] in nature. Because of their unique mechanical properties, they have a large variety of applications, such as in the modeling of mechanical properties [19,22], drug delivery [23,24], electronics [25], the modifier of resin [26], and biomimetics [27].…”

Morphology and Mechanical Properties of Fossil Diatom Frustules from Genera of Ellerbeckia and Melosira

“…However, because the size of most diatom species ranges from 3 µm to 200 µm [ 26 ], traditional mechanical test methods struggle to characterize individual frustules. Recently, new approaches on micro- and nanomechanical tests have been developed and used to study the mechanical behavior of frustules [ 20 , 27 , 28 , 29 ]. Indentation by atomic force microscopy (AFM) on pennate and centric diatoms showed that the elastic modulus varied from several to hundreds GPa depending on the test locations [ 27 , 28 ].…”

“…Indentation by atomic force microscopy (AFM) on pennate and centric diatoms showed that the elastic modulus varied from several to hundreds GPa depending on the test locations [ 27 , 28 ]. In situ microindentation, in combination with scanning electron microscopy (SEM) on pennate diatom frustules ( Didymosphenia geminata ), shows that the applied load to achieve elastic deformation on the epivalve surface ranges from 100 µN to 1000 µN [ 29 ]. In three-point bending experiments on the centric diatom ( Coscinodiscus sp.…”

“…Furthermore, one of the most critical points for the application of fossil frustules in MMCs is to understand the exact intricate 3D morphologies of the frustules. SEM, also in combination with a focused ion beam (FIB), and AFM, were used to study the morphologies of the diatom frustules [ 9 , 10 , 28 , 29 , 31 , 32 ]. However, these techniques cannot access the interior structure nondestructively.…”