Superductile, Wavy Silica Nanostructures Inspired by Diatom Algae

Abstract

The interest in nanoscale biomimetics and biologically inspired designs for structural and mechanical applications has significantly increased over the past few years. One reason for this lies in the apparent benefits that come from nanomaterials, including enhanced mechanical properties and multifunctionality. Yet, many of these materials are produced from generally expensive methods with possible toxic byproducts. But what if we could harness the benefits of nanomaterials through efficient and environmentally friendly mass production? Here, we use diatoms as a design paradigm to create novel nanoscale materials that encompass surprising mechanical properties, by utilizing a merger of structure and Biology implements intriguing structural design principles that allow for attractive mechanical properties-such as high strength, toughness, and extensibility despite being made of weak and brittle constituents, as observed in biomineralized structures. For example, diatom algae contain nanoporous hierarchical silicified shells, called frustules, which provide mechanical protection from predators and virus penetration. These frustules generally have a morphology resembling honeycombs within honeycombs, meshes, or wavy shapes, and are surprisingly tough when compared to bulk silica, which is one of the most brittle materials known. However, the reason for its extreme extensibility has not been explained from a molecular level upwards. By carrying out a series of molecular dynamics simulations with the first principles-based reactive force field ReaxFF, the mechanical response of the structures is elucidated and correlated with underlying deformation mechanisms. Specifically, it is shown that for wavy silica, unfolding mechanisms are achieved for increasing amplitude and allow for greater ductility of up to 270% strain. This mechanism is reminiscent to the uncoiling of hidden length from proteins that allows for enhanced energy dissipation capacity and, as a result, toughness. We report the development of an analytical continuum model that captures the results from atomistic simulations and can be used in multiscale models to bridge to larger scales. Our results demonstrate that tuning the geometric parameters of amplitude and width in wavy silica nanostructures are beneficial in improving the mechanical properties, including enhanced deformability, effectively overcoming the intrinsic shortcomings of the base material that features extreme brittleness.

Stochastic Interdigitation as a Toughening Mechanism at the Interface between Tendon and Bone

“…Interdigitations are present throughout nature at interfaces such as those found in nacre (22,23), armored fish (24), algae (25), and sutures within the skull (26) and jaw (27). Interdigitations are believed to improve load transmission and increase energy absorption of the interfaces between bones in the skull (28).…”

Structure and mechanical properties of selected protective systems in marine organisms

“…Silica (SiO 2 ) is most commonly expressed within the biological materials of sponges and diatoms [76][77][78][79][80][81], and is generally found in its amorphous form [76][77][78][79]. The biomineralization of SiO 2 follows different processes in different organisms.…”

Influence of geometry on mechanical properties of bio-inspired silica-based hierarchical materials

“…Several earlier studies have focused on studying these properties in light of their hierarchical nature [11][12][13][14][15][16]. With the advancement of computational tools, in silica studies have also become a popular tool used to gain fundamental insight into the design principles employed by nature in developing advanced materials from primitive building blocks [17][18][19][20][21][22]. In [17] it was shown that the nanometer size of certain structural features in mineralized structures might be selected to optimize local flaw tolerance.…”