The Rise of (Chiral) 3D Mechanical Metamaterials.

Janet Reinbold,Martin Wegener,Alexander Münchinger,Tobias Frenzel

doi:10.3390/ma12213527

Abstract

On the occasion of this special issue, we start by briefly outlining some of the history and future perspectives of the field of 3D metamaterials in general and 3D mechanical metamaterials in particular. Next, in the spirit of a specific example, we present our original numerical as well as experimental results on the phenomenon of acoustical activity, the mechanical counterpart of optical activity. We consider a three-dimensional chiral cubic mechanical metamaterial architecture that is different from the one that we have investigated in recent early experiments. We find even larger linear-polarization rotation angles per metamaterial crystal lattice constant than previously and a slower decrease of the effects towards the bulk limit.

Highlights

Consider the three-dimensional (3D) micro-lattice shown in Figure 1 as an example
Concerning the fabrication details, we refer the reader to Refs. [18,21] and the early work on “dip-in” mode [26], which is widely used for the making of microstructured polymer-based 3D mechanical metamaterials by 3D laser nanoprinting [27]
After briefly reviewing the history and the perspectives of the field of 3D mechanical metamaterials, we have presented our original results on the design, calculation of phonon band structures, manufacturing by 3D laser microprinting, and ultrasound experimental characterization of one type of chiral 3D mechanical metamaterial exhibiting acoustical activity—the mechanical counterpart of optical activity

Summary

Introduction

Consider the three-dimensional (3D) micro-lattice shown in Figure 1 as an example. When giving talks to a broad audience, an ever-reoccurring question is whether one should see such an artificial crystal as a “structure” or as a “material”. The true answer is that both viewpoints are permissible. Treating such rationally designed lattices as material or “metamaterial” has the advantage that the properties of the lattice can be mapped onto simple effective-medium parameters, such as, for example, the effective Young’s modulus in mechanics. Working further with these effective-medium parameters to design systems eases the treatment compared to looking at an entire system as a microor nanostructure. Computer chips are successfully designed by using electric conductivities etc., whereas the design would likely be impossible if the entire computer chip needed to be treated on the level of individual atoms

Methods

Discussion

Conclusion