Reduce order modeling of soft hierarchical multistable metasheets with applications

Reconfigurable structures and soft metamaterials have introduced new opportunities for robot design, shape programmability and embedded sensing. Recently, patterned metamaterials consisting of reconfigurable bistable units have gained interest due to their capability of exhibiting different energy minima, activation path dependency, and influence of local prestress in its global shape. As the unit cells can be reversibly inverted at the local scale, multiple stable shapes at the global scale are generated. These shapes are highly dependent on the unit geometry, inversion sequence, the number of units, and unit spatial distribution, which makes them difficult to analyze, predict and count. Given this, more simple yet robust models need to be utilized to predict the final state of the structure, enabling faster analysis and design.

This work analyzes the global stable states of our metasheet by investigating the interrelations between units and their spatial arrangement. We utilized a reduced-order model base on spring lattices to determine the final shape of our metastructure in terms of the number of units, distribution, and unit cell geometric parameters. We further examine the interaction between units and its effect on the final shape and its role in the generation of geometrically frustrated stable states. Furthermore, we examine the effect of inversion path and unit interactions in different applications, such as soft multistable actuators and reconfigurable structures. This opens a route for the fast design of multistable soft robots and shape targeting in soft metamaterials.