Rapid Pneumatic Control of Bimodal, Hierarchical Mechanical Metamaterials

Recent attention to pneumatically pressurized mechanical metamaterials has identified opportunity for large shape change and mechanical properties adaptation through the collective exploitation of reconfigurable internal structures and enclosed cavities. Yet, many of these ideas are found to act in smooth, continuous ways at moderate rate. This research explores a new class of bimodal, hierarchical mechanical metamaterials that exemplify rapid change of mechanical behavior by exploiting pneumatic pressure as a means to cross bifurcation. A lattice structure with periodic square cavities is presented as a model metamaterial to highlight important design considerations and mechanical behavior. An analytical model is formed to delineate the multimodal boundaries in a high‐dimensional parameter space, while numerical simulations and experiments confirm the presence of each modal characteristic. The studies reveal the high rate of change afforded by this embodiment of pressurized mechanical metamaterials and confirm the origin lay in harnessing elastic instability. Extensions to the idea are compared against the Kutzbach–Grübler criteria to articulate how other metamaterial networks may be leveraged in this way. The outcomes of this research may inspire methods for high‐rate shape and properties change via multimodal mechanical metamaterial assemblies, such as for soft robotic platforms.