Recent Progress on 3D Chiral Mechanical Metamaterials

We review our recent progress on three-dimensional (3D) microstructured chiral mechanical metamaterials. These architectures have been made by state-of-the-art 3D laser nanoprinting and more recently also by rapid multi-focus multi-photon 3D laser nanoprinting. For the latter, the metamaterials contain more than one hundred thousand unit cells and more than three hundred billion voxels.

Concerning the static regime, we will present novel architectures that allow for bringing the push-to-twist conversion effects previously reported by us to much larger absolute values at larger numbers of unit cells. Specifically, the twist/strain can be tailored to linearly increase up to a characteristic number of unit cells, beyond which the twist/strain asymptotically decays inversely with the number of unit cells.

Regarding the dynamic regime, we will review our experimental and theoretical results on acoustical activity, the elastic counterpart of optical activity. We will emphasize obtaining isotropic chiral behavior in truss-based 3D quasicrystals, in triclinic 3D crystals, and in cubic 3D crystals. The latter two possibilities exploit the idea of tailored “accidental” degeneracies.