Fig. 1. Schematic illustration of the proposed reconfigurable metamaterial and its constituent meta-atom. (a) 3D reconfiguration mechanism and incidence polarization states of electromagnetic metamaterial. (b) Structural composition and geometrical parameters of the proposed meta-atoms A and B.

Fig. 2. Simulated deformation and transmittance of the proposed reconfigurable metamaterials. (a) Schematic reconfiguration of meta-atoms and their stress distributions calculated by FEA. Transmittance components of (b) planar metamaterial consisting of meta-atom A or B, and (c), (d) 3D deformed (ε=40%) metamaterial consisting of meta-atoms A and B under circularly polarized incidence. (e) Circularly co- and cross-polarized transmittance difference of deformed metamaterials A and B.

Fig. 3. Fabricated reconfigurable metamaterial samples and their measured transmittance spectra. (a) Fabricated metamaterial sample and its flexible characteristics (scale bars, 9 mm). (b) 2D and 3D morphologies of fabricated samples corresponding to meta-atoms A and B (scale bars, 18 mm). (c) Schematic and physical view of far-field measurement system. Measured transmittance components of metamaterial A in (d) planar state and (e) 3D deformed state, and metamaterial B in (f) planar state and (g) 3D deformed state.

Fig. 4. Physical mechanisms of the spin-dependent transmittance in the deformed meta-atoms. (a) Simulated surface current distributions and (b) calculated scattering power corresponding to electric dipole (P), magnetic dipole (M), toroidal dipole (TD), and magnetic quadrupole (MQ) of 3D meta-atom A under LCP and RCP incidence. (c) Simulated surface current and (d) calculated multipolar scattering power of 3D meta-atom B under LCP and RCP incidence.

Fig. 5. Design and characterization of a reconfigurable metalens based on 2D-to-3D buckling. (a) Schematic illustration of structural composition and double-foci characteristics of free metalenses. (b) Circularly cross-polarized transmittance phases of undeformed meta-atoms A with various orientations. (c) Transmittance amplitude ratio of meta-atom A and meta-atom B at 10 GHz. (d) Calculated phase distribution on the metalens plane and overall exhibition of designed structure. (e) Full-wave simulated electric field intensity on the focusing plane z1=200  mm under ε=0% and z2=100  mm under ε=40%. (f) 2D and 3D morphology exhibition of fabricated metalens sample. (g) Near-field scanning imaging system for measuring spatial distribution of electric field behind the metalens sample. (h) Measured electric fields and normalized intensity (along y=0  mm) of 2D and 3D metalens.

Fig. 6. Circularly cross-polarized transmittance of meta-atom A and B and their amplitude ratio under (a) ε=0% and (b) ε=40%. Co- and cross-polarized transmittance amplitude of 3D (a) meta-atom A and (d) meta-atom B.

Fig. 7. Fabrication process of 2D-to-3D buckling deformable electromagnetic metamaterials.

Fig. 8. (a) Amplitude and (b) phase of 3D buckled metamaterial A of the co- and cross-polarized transmittance under x-polarized incidence. (c) Amplitude and (d) phase of 3D metamaterial B of the co- and cross-polarized transmittance under y-polarized incidence.