In Situ Manipulation and Micromechanical Characterization of Diatom Frustule Constituents Using Focused Ion Beam Scanning Electron Microscopy

• Published in: Small methods 2021-12, Vol.5 (12), p.e2100638-n/a
• Main Authors: Soleimani, Mohammad, Breemen, Lambèrt C.A., Maddala, Sai P., Joosten, Rick R. M., Wu, Hanglong, Schreur‐Piet, Ingeborg, Benthem, Rolf A.T.M., Friedrich, Heiner
• Format: Article
• Language: English
• Subjects: Biomechanical Phenomena; biosilica; diatom frustule; Diatoms - ultrastructure; Elastic Modulus; Finite Element Analysis; hybrid materials; in situ deformation; micromanipulation; Microscopy, Electron, Scanning; Microtechnology - instrumentation; Nanostructures; Spectrometry, X-Ray Emission
• ISSN: 2366-9608; 2366-9608
• DOI: 10.1002/smtd.202100638

Biocomposite structures are difficult to characterize by bulk approaches due to their morphological complexity and compositional heterogeneity. Therefore, a versatile method is required to assess, for example, the mechanical properties of geometrically simple parts of biocomposites at the relevant length scales. Here, it is demonstrated how a combination of Focused Ion Beam Scanning Electron Microscopy (FIB‐SEM) and micromanipulators can be used to isolate, transfer, and determine the mechanical properties of frustule constituents of diatom Thalassiosira pseudonana (T.p.). Specifically, two parts of the diatom frustule, girdle bands and valves, are separated by FIB milling and manipulated using a sharp tungsten tip without compromising their physical or chemical integrity. In situ mechanical studies on isolated girdle bands combined with Finite Element Method (FEM) simulations, enables the quantitative assessment of the Young's modulus of this biosilica; E = 40.0 GPa. In addition, the mechanical strength of isolated valves could be measured by transferring and mounting them on top of premilled holes in the sample support. This approach may be extended to any hierarchical biocomposite material, regardless of its chemical composition, to isolate, transfer, and investigate the mechanical properties of selected constituents or specific regions. A method for in situ manipulation and micromechanical characterization of materials using focused ion beam scanning electron microscopy with micromanipulators is presented. In combination with Finite Element Method simulation, this method enables assessment of the mechanical properties such as Young's modulus of individual components of hierarchical biocomposites on micrometer length scales.