Mechanically Tunable Electromagnetic Metamaterials Based on Chains of Tension-rotation Coupling Units with Exceptional Reconfiguration Capability.

Controlling the out-of-plane rotation of split-ring resonators (SRRs) represents an effective strategy to realize mechanically tunable electromagnetic (EM) materials. However, designing structures that can achieve substantial angular rotations via straightforward stretching operations while keeping the resonators intact remains a challenge. Here, a mechanically tunable EM metamaterial constructed from parallel chains of tension-rotation units that enable substantial out-of-plane rigid rotations exceeding 120° of the SRRs through simple stretch is reported. Theoretical, numerical, and experimental studies are conducted to reveal the deformation mechanism and quantify the relationship between tensile strain and rotation angles of SRRs. Comprehensive experimental and numerical studies show that the proposed metamaterial can extensively modulate the transmissions of both linearly and circularly polarized waves. Specifically, the transmission of TE wave exhibits a distinctive two-stage increasing-decreasing behavior, and the CD presents a unique zero-positive-zero-negative profile during stretching, which are not easily accessible by existing mechanically tunable EM metamaterials due to their limited deformation capabilities. Moreover, structural reconfiguration of chain arrangements enables tunable resonance frequencies while maintaining the frequency position of maximum CD, demonstrating robust preservation of the dominant chiral eigenmode. This study provides a valuable design strategy for developing mechanically tunable EM metamaterials with high tunability and multifunctionality.