Phononic Bandgap Programming in Kirigami

TL;DR

This paper demonstrates how sequencing mechanical bits in kirigami structures can program elastic wave bandgaps, enabling tunable phononic properties through design and stretching, with theoretical and experimental validation.

Contribution

It introduces a novel method to program phononic bandgaps in kirigami by sequencing stable mechanical states, supported by an algorithm and theory linking sequence to bandgap properties.

Findings

Sequencing (0) and (1) states alters phononic bandgap frequencies.

Theoretical predictions match experimental results.

Global stretching fine-tunes the programmed bandgaps.

Abstract

This study investigates the programming of elastic wave propagation bandgaps in a kirigami material by intentionally sequencing its constitutive mechanical bits. Such sequencing exploits the multi-stable nature of the stretched kirigami, allowing each mechanical bit to 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. To this end, 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 a versatile approach to 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.