Nanomechanical Testing of Diatoms

Abstract

Diatoms, a major group of algea, are protected by a nanostructured shell, built with a design that exceeds the capabilities of human engineering. These shells, termed frustules, consist of biosilica and give the organism more than just a physicalarmor. Light-harvesting properties combined with great mechanical and bacterialprotection makes diatoms interesting in scientic research.This thesis presents the diatoms and their exceptional properties. A diatom cantileverbending test is initiated and could potentially be the rst test method to determine the true material properties of biosilica in diatoms. Cantilever beams are isolated from compact foramen layers with sizes down to 0,35 1,54 mm. A structural characterisation is initiated to identify internal geometries in the frustules of the Coscinodiscus Centralis. The initial measurements indicates that the internal elevation in the C. Centralis is not a size-consistent component. Still, clear trends are seen in their mechanical response when frustules with dierent pretreatment are tested by nanoindentation. Observations after indentations performed in a picoindenter are indicating that the foramen pores are important to hinder crack propagation in diatom frustules.