Diatoms are single-celled microalgae with unique cell walls (frustules) composed of amorphous hydrated silica composites and an organic layer. Due to their interesting structure and morphology, consisting of uniform and symmetrically arranged pores, they can inspire the development of new materials for nanotechnology applications.

The 3D structure characterization of a centric diatom frustule of the species Actinoptychus senarius, with a diameter of about 60 μm, was obtained using the lab-based X-ray microscope Xradia 810 Ultra, here referred to as nanoCT. The nanoCT is a resourceful tool for the 3D characterization of samples down to 150 nm of resolution within a field of view of 65 μm. Due to the low energy X-ray source (5.4 keV) and Zernike phase contrast, this X-ray microscope is ideal for the analysis of low-density samples such as soft tissues and polymers. In addition to structural characterization, a loading stage setup mounted on the sample rotation stage allows for in situ mechanical experiments and for the observation of microstructural changes in the sample as a function of the loading and time.

The structural characterization of the frustule enabled the quantification of the pore’s sizes, proportion and distribution within the specimen. Furthermore, the in situ experiment allowed the observation of fracture evolution at different levels of loading. The cracks originated in the porous diatom frustule and propagated along a path of connecting pores, eventually fracturing the center of the frustule at a later stage.