Bio-inspired seismic metamaterials: Time domain simulations in transformed crystals

TL;DR

This paper introduces transformation crystallography for designing seismic metamaterials with complex geometries, analyzing elastic wave propagation through simulations, and demonstrating potential applications in geophysics and biophysics.

Contribution

It presents a novel approach combining geometric transforms with crystal structures to design seismic cloaks and explores their analogies with nanoscale metamaterials.

Findings

Transformation techniques enable cloaks with diverse geometries.

Simulations show effective elastic wave control in transformed crystals.

Field data supports practical application of bio-inspired seismic metamaterials.

Abstract

We introduce the concept of transformation crystallography which consists of the application of geometric transforms to periodic structures. We consider motifs with three-fold, four-fold and six-fold symmetries according to the crystallographic restriction theorem. Furthermore, we define motifs with five-fold symmetry such as quasi-crystals generated by a cut-and-projection method. We analyze elastic wave propagation in the transformed crystals and (Penrose-type) quasi-crystals with the finite difference time domain freeware SimSonic. We consider geometric transforms underpinning the design of seismic cloaks with square, circular, elliptical and peanut shapes in the context of triangular, square and honeycomb crystals. Interestingly, the use of morphing techniques leads to the design of cloaks with interpolated geometries reminiscent of Victor Vasarely's artwork. Employing the case of transformed graphene-like (honeycomb) structures allows one to draw useful analogies between large-scale seismic metamaterials such as soils structured with columns of concrete or grout with soil and nanoscale biochemical metamaterials. We further point out similarities between cloaks for elastodynamic and hydrodynamic waves and cloaks for diffusion (heat or mass) diffusion processes, notably with respect to invisibility and protection. Experimental data extracted from field test analysis of soil structured with boreholes demonstrates the application of bio-inspired seismic metamaterials. We conclude that these novel materials hold strong applications in biophysics and geophysics.