Phononic Bandgap Programming in Kirigami By Unique Mechanical Input Sequencing

This study investigates the programming of elastic wave propagation bandgaps in periodic and multi-stable metamaterials by intentionally and uniquely sequencing its constitutive mechanical bits. To this end, stretched kirigami is used as a simple and versatile testing platform. Each mechanical bit in the stretched kirigami can switch between two stable equilibria with different external shapes (aka. "(0)" and "(1)" states). Therefore, by designing the sequence of (0) and (1) bits, one can fundamentally change the underlying periodicity and thus program the phononic bandgap frequencies. This study develops an algorithm to identify the unique periodicities generated by assembling "n-bit strings" consisting of n mechanical bits. Based on a simplified geometry of these n-bit strings, this study also formulates a theory to uncover the rich mapping between input sequencing and output bandgaps. The theoretical prediction and experiment results confirm that the (0) and (1) bit sequencing is effective for programming the phonic bandgap frequencies. Moreover, one can additionally fine-tune the bandgaps by adjusting the global stretch. Overall, the results of this study elucidate new strategies for programming the dynamic responses of architected material systems.