NANOMECHANICAL TESTING OF DIATOMS

A test scheme to test micro-beams from diatom frustule has been developed. The method is capable of testing both complete beams and beams made from the individual layers of the frustule. The biosilica is shown to be a very brittle material with an average fracture stress of 336 +- 73 MPa and a flexural modulus of 5.72 +- 2.9 GPa. A comparison of the mechanical properties of the different layers has been performed and shows that the different structural parts greatly influence the overall mechanical properties. Additionally the mechanical properties of frustules that have undergone different chemical treatments have been investigated. The initial results indicate that the softer chemical treatment yields a stiffer biosilica. The challenges of computational modeling of biosilica has been discussed and initial FEM-modeling shows that the porous structure reduces the stiffness of the overall structure. Further development of a combined experimental and computational test scheme is suggested. In addition an AFM-study and nanoindentation tests were performed on the frustules.