Light-activated bandgap modulation of active tunable metamaterials with folded structure

Abstract This study presents the design of an active tunable metamaterial beam constructed from a folded structure fabricated by light-activated shape memory polymer (SMP). The stiffness of light-activated SMP is modulated by ultraviolet (UV) illumination, a phenomenon attributed to the photo-elastic coupling response. The design integrates the Euler–Bernoulli beam model with local resonance theory to achieve tunable mechanical properties. Through comprehensive theoretical analysis and numerical simulation, the bandgap ranges of the tunable metamaterial beam across various configurations are systematically calculated. Additionally, the intricate relationships between the bandgap, UV illumination time, and geometric parameters are explored and analyzed. The results reveal that both the upper and lower limits of the bandgap shift toward higher frequencies as the illumination time increases or the number of structural folds grows, thereby demonstrating active bandgap tuning capability of the metamaterial beam. Finally, experimental validation confirms the vibration suppression efficacy of the light-activated metamaterial beams. These beams exhibit pronounced vibration damping and isolation effects within frequency bands near their intrinsic resonance. Notably, the bandgap frequency range of the light-activated metamaterial beams can be substantially modified through UV irradiation for different time, or by augmenting the number of structural creases. Compared to traditional fixed-bandgap metamaterials, this design achieves a 10% upward bandgap shift under 90 s UV irradiation and a 150% bandwidth increase using double-layered folds, with a response speed of seconds—significantly outperforming the minute-scale response of thermal actuation. This rapid, remote, non-contact tuning capability facilitates applications in lightweight vibration reduction in aerospace, vibration isolation of precision instruments, and dynamic control of flexible robots.