Deformation Modes and Structural Response of Diatom Frustules

Abstract

The ubiquitous diatoms, single-celled algae with porous silica frustule (shell) morphology and features spanning multiple length scales, offer a promising foundation to convert knowledge of biological structures into novel design techniques. Diatom frustules are often found in nature with distinct deformation patterns suggesting the involvement of mechanical interactions in their morphogenesis. Understanding this phenomenon can lead to potential manufacturing techniques based on the micromanipulation of bio-inspired structures. In this study, the mechanics of centric diatom frustules was investigated ALEJANDRO GUTIÉRREZ et al. 106 using the finite element method (FEM) in combination with morphology and material properties obtained from scanning electron microscopy (SEM) and mechanical tests respectively. SEM micrographs of a marine diatom, Coscinodiscus sp., have allowed the classification of specific deformation patterns frequently observed on these frustules. To elucidate the nature of these deformations, a computer aided design (CAD) model approximating a centric diatom frustule was created. Using shear-deformable frustule finite elements and diatom-specific Young's modulus, critical buckling load and modal analysis of the diatom model were performed to investigate possible correlations of the deformation modes with observed morphologies. Results reveal that the first ten deformation modes correlate noticeably well with deformation patterns observed through SEM. Additionally, FEM models were used to study the relation between diatom morphology and mechanical behaviour. A quadratic relation was established between frustule pore size and critical buckling load as well as a cubic relation between frustule thickness and critical buckling load, reported for the first time in this study. The findings in this research provide insights into the mechanical response of diatom frustules that can aid the realization of tailored properties in new bio-inspired materials, in particular for nanotechnology applications, but also for advanced metamaterials and optomechanical devices.

Silicified cell walls as a defensive trait in diatoms

“…This dependency of copepod grazing mortality on silica content is consistent with experimental measurements as well as finite-element method (FEM) simulations, demonstrating that the mechanical strength of diatom shells increases with increasing silica content [23,29,46,47]. It is also consistent with scaling arguments (see below) that both the fracture strength and the critical buckling load of a diatom shell increase approximately with the cell wall thickness raised to the power of 3.…”

“…Attempting to approach the morphology of a diatom shell, assume the column has a cross-section h  b with b ) h (i.e. a plate of thickness h), then the buckling load would scale as P % h 3 b/L 2 % h 3 just as suggested by the FEM simulation of [47]. For this case, using the criterion P % h 3 b/L 2 % constant (i.e.…”

FEM exploration of the potential of silica diatom frustules for vibrational MEMS applications

“…the displacements shown are normal to the plane of the girdle band. The vibration mode shapes for the centric diatom valve are similar to those of a circular plate [28,29], whilst for the pennate diatom Synedra acus. they are similar to that of an extended rod.…”

The Coarse Microstructure of Medium‐Carbon Microalloyed Steel Crankshafts: Formation Mechanism and Finish Forging Control

“…[7][8][9][10][11][12][13][14][15] The aforementioned two methods can increase the high angle boundaries (≥15 ) in steels, which can provide effective barriers to cleavage fracture and improve the toughness. [16][17][18] Although, as shown in Figure 1, the titanium microalloying and IGF technologies have been applied, the coarse microstructure in the main journal of a crankshaft is still not eliminated.…”