MECHINOID is an INTERREG funded project granted to  Dirk Müter, supervised by Henning. O. Sørensen and co-supervision of Stephen Hall (Lund University, Sweden) which ran from 09/2016 to 02/2017.

Title: “Nanomechanics of echinoid functional biomineralized materials”

Summary: In this project, we set out to investigate the micro- and nanostructure of sea urchin spines and their mechanical properties using both laboratory based microtomography (µCT) and synchrotron nanotomography (nanoCT) imaging. We found that the spines of the Edible Sea Urchin (Echinus esculentes) consist of a foam-like network composed of struts with thickness in the range of 5-10 µm and local porosity of between 30 and 65% (see Figure below). The network is highly anisotropic and shows a preferred direction aligned with the axis of the spine. Utilizing the long experience of our collaboration partner at Lund University, we were able to set up a computer simulation (finite element method) that simulates deformation of small regions in our tomography data under an external pressure. From these simulations, we calculated a material constant, Young’s modulus, for different regions in the spine. Plotting Young’s modulus over porosity shows that the spine performs mechanically close to an ideal foam and retains good mechanical properties even at very high porosity. Furthermore, we found that Young’s modulus is much larger along the preferred direction of the microstructure which can be seen as an evolutionary adaptation to strengthen the spines in the direction of the expected load, e.g. by predators. In addition to an increased insight into nature’s design strategies, we hope that our work can inspire synthetic materials that make use of the spines unique architecture.

Conference contributions:
InterPore, Rotterdam (Netherlands) 2017 (Poster Pitch)
“X-ray Nanotomography of Sea Urchin Spines”