Architected hierarchical kirigami metallic glass with programmable stretchability

Despite the recent achievements in the stretchability of kirigami metallic glasses, relevant research is still mainly relying on the single-level kirigami structure. In our work, three different hierarchical levels of patterns were developed for kirigami metallic glass structures for both strip and square units. The degree of freedom that reflects the availability for morphing is shown to be a key factor affecting the mechanical response of the hierarchical metallic glasses. It is found that a high hierarchical order with a large degree of freedom leads to the high stretchability of kirigami metallic glasses. Kirigami metallic glasses, designed with square units, with a large degree of freedom show high stretchability compared to those designed with strip units, with a small degree of freedom, at the same hierarchical level. Our study, combining the degree of freedom in the hierarchical construction, highlights the potential for a multilevel architected structure as a programmable block for stretchable mechanical metamaterials.