Controllable Deformation Modulated Multi-Functionality for Phase-Gradient Metamaterials

Tunable metamaterials offer versatile approaches to achieve the dynamic manipulation of electromagnetic waves with various dimensionality. Recently, mechanical approaches have been extensively employed to construct reconfigurable metamaterials with simple composition and superior mechanical characteristics. Mechanical modulation methods in phase-gradient metamaterials are even more worthy of being investigated to facilitate valuable applications. Here, an in-plane rotational deformation principle is proposed to assist the structural design of reconfigurable phase-gradient metamaterials by integrating split ring resonators (SRRs) on the hyperelastic kirigami substrate. The orientations and split angles of SRRs are explored to manipulate the amplitudes and phases of cross-polarized transmittance under x-polarized incidence, respectively. The tensile strains dramatically modulate the amplitudes yet not the gradient phase. As proof-of-concept, a reconfigurable metalens is elaborately designed to realize tunable focus location and number by regulating the transmittance amplitudes of meta-atoms via stretching the kirigami substrate. Furthermore, a holographic metamaterial is developed to perform dynamic hologram on the imaging plane under the strain 0% and 40%. The proposed mechanical deformation principle offers a promising platform for dynamic manipulation of the wavefront and may promote the conformal and flexible designs in certain cases and enlarge the potential applications of meta-devices in imaging and information encryption. The modulation of phase-gradient metamaterials is demonstrated by the in-plane rotational deformation of split ring resonators integrated on a kirigami hyper-elastic substrate. Compared with previous kirigami metamaterials replying on the out-of-plane deformation, this mechanical reconfiguration principle only needs the in-plane deformation and is successfully applied toward advanced applications in dynamic metalenses and meta-holograms.image