Light-induced membrane-type locally resonant metamaterial beam with tunable bandgap

The locally resonant metamaterial beam incorporating light-induced shape memory polymer (SMP) membranes as springs is proposed to achieve tunable bandgap properties in this work. The designed adaptive metamaterial can obtain variable bandgap in low-frequency range through non-contact control via ultraviolet light illumination. First, the Young’s modulus of light-induced SMP is experimentally investigated. Subsequently, a membrane-type locally resonant metamaterial beam with light-induced SMP is proposed, and an analytical model is established by treating the SMP membrane as a spring. The transmission spectra of certain resonator are compared with finite element method to validate the accuracy of the model. Based on this model, the effects of various parameters, such as the membrane radius, mass, and mass ratio of the substrate and vibrator, on the transmission characteristics are systematically examined. A base-excited metamaterial beam prototype with five resonators is designed and fabricated. Experimental results confirm that the bandgap can be tuned with different light exposure time, achieving a maximum 63% shift in the lower bound of the bandgap. Given that the bandgap shift is governed by the square root of Young’s modulus, different kinds of light-induced SMPs reported in the literatures are suggested to further expand the tunable bandgap range.