A new structure-property connection in the skeletal elements of the marine sponge Tethya aurantia that guards against buckling instability

Abstract

We identify a new structure-property connection in the skeletal elements of the marine sponge Tethya aurantia. The skeletal elements, known as spicules, are millimeter-long, axisymmetric, silica rods that are tapered along their lengths. Mechanical designs in other structural biomaterials, such as nacre and bone, have been studied primarily for their benefits to toughness properties. The structure-property connection we identify, however, falls in the entirely new category of buckling resistance. We use computational mechanics calculations and information about the spicules’ arrangement within the sponge to develop a structural mechanics model for the spicules. We use our structural mechanics model along with measurements of the spicules’ shape to estimate the load they can transmit before buckling. Compared to a cylinder with the same length and volume, we predict that the spicules’ shape enhances this critical load by up to 30%. We also find that the spicules’ shape is close to the shape of the column that is optimized to transmit the largest load before buckling. In man-made structures, many strategies are used to prevent buckling. We find, however, that the spicules use a completely new strategy. We hope our discussion will generate a greater appreciation for nature’s ability to produce beneficial designs.

Shaping highly regular glass architectures: A lesson from nature

“…1A ). These spicules, arranged in bundles that radiate from the center of this subspherical sponge, can reach a diameter of 35 μm and a length of 2 mm ( 26 , 27 ). In accordance with the hexagonal lattice of the proteinaceous axial filament in demosponges, its morphology in cross section exhibits a sixfold symmetry and, in some instances, appears as a perfect hexagon (inset in Fig.…”

Optical Properties of Nanostructured Silica Structures From Marine Organisms

“…Studies on the needle-shaped structures called strongyloxea spicules (axisymmetric silica rods) of Tethya aurantia have shown that spicule's tapering structures enhanced the buckling resistance compared to the same cylindrical structure (Monn and Kesari, 2017). Strongyloxea spicules have a strong Young's modulus of 72 GPa, which might be explained by the gathering of spicules into bundles to increase mechanical properties.…”

“…Strongyloxea spicules have a strong Young's modulus of 72 GPa, which might be explained by the gathering of spicules into bundles to increase mechanical properties. It was also proposed that structure-property connection is also related to buckling resistance, and spicule's tapering structures can be considered as an optimal form for this purpose (Monn et al, 2015;Monn and Kesari, 2017). Overall, spicules have been shown to present remarkable mechanical properties in different axes as buckling resistance and toughness enhancement.…”

“…The overall density of the silica wall also affects the overall sinking rate of diatoms, and help the cells in escaping from predators and parasites, avoiding high light intensity, or finding new resource areas (Raven and Waite, 2004). The silica spicules provide support and defense to marine sponges (Burns and Ilan, 2003;Rohde and Schupp, 2011), correspond to an import feature that can serve as anchoring structure to hold on the sea floor (Ehrlich et al, 2010b;Monn et al, 2015;Monn and Kesari, 2017). However, the exact roles and properties of such silica structures for light perception, UV protection or signal transduction has been rarely investigated in vivo.…”

Probing micron-scale distributed contortions via a twisted multicore optical fiber

“…Among the EM waveguide designs, optical fibers represent a highly attractive platform for developing contortion sensors, owing to a variety of available design parameters and configurations, a shielded transport of EM radiation, and an opportunity for ultralong length distributed sensing operation. [27][28][29] The optical-fiber contortion sensors may employ gratings, [29][30][31][32][33][34][35][36][37][38][39] modal interference, [40][41][42][43][44][45] radiationlosses, [46][47][48][49][50][51][52] or nonlinear effects to detect and measure the probed contortions. 10,26,53,54 In the past, optical fiber sensors for a distributed measurement of such parameters as temperature, pressure, strain, etc., have been extensively studied.…”