Publication already discussed:
Large recoverable elastic energy in chiral metamaterials via twist buckling | Nature
Samples
The rubber chiral metacell in Fig. 4a features N = 8 rods with r = 1.5 mm, whereas the titanium version has N = 20 and r = 0.6 mm.
In Fig. 4c, chiral-20° has R = 5.5, 2r = 1.8, α 0 = 20°, h 0 = 20 mm. Chiral-50° has R = 6, 2r = 1.7, α 0 = 50°, h 0 = 20 mm. E s ≈ 5.5 MPa for rubber samples in Fig. 4e, whereas other rubber samples have E s ≈ 15 MPa.
Experiments
Cyclic compression experiments were performed. The rods in newly fabricated metal samples are initially straight. However, after the first compressive cycle, the all-metal samples exhibit some residual plastic deformation. In this case, α 0 increases, and the rod becomes slightly bent.
These objects therefore appear to be made of metal.
Maybe other materials could be used? Tethers with a metallic core as chiral metamaterial?