Speaker
Description
As the most common type of phytoplankton, diatoms are unicellular microalgae responsible for producing about 20-25% of atmospheric oxygen, playing a central role in global carbon and silica cycles. Their siliceous shells, called frustules, exhibit complex porous micro and nano-architectures combining remarkable structural regularity yet with apparent biological disorder. Despite the great inter-disciplinary attention brought upon these organisms, the apparent order in frustules is lacking consistent systematic characterization. In this work, we provide a quantitative order classification of these natural microstructures using the framework of hyperuniformity. Born from statistical and material physics, the latter helps describe and characterize the orderliness of complex media at the boundaries of order and disorder; a compelling application for analyzing and classifying disordered yet regular patterns, such as those of diatoms. High-resolution scanning electron microscopy (SEM) images from 21 diatom genera spanning the 3 major taxonomic classes were analyzed through complementary real- and reciprocal-space metrics, including spectral density scaling and bond-orientational order parameters. All investigated frustules were found to display hyperuniform organization, distributed mostly as strong (Class I) and weak (Class III) hyperuniform regimes. This taxonomy reveals how biologically evolved porous architectures balance local geometric order with large-scale disorder resilience. Beyond evident statistical and biological interests, the results suggest that diatom frustules constitute a natural library of architected hyperuniform media, known for featuring exotic wave physics features found in crystals, such as isotropic Bragg bandgaps and topological mode protection. As such, diatoms can offer design inspiration for lightweight structures and disorder-based crystals and metamaterials with tailored mechanical or wave-interaction properties.