Multi-step self-guided pathways for shape-changing metamaterials

TL;DR

This paper introduces shape-changing mechanical metamaterials capable of autonomous multi-step reconfigurations under uniform compression, achieved through nonlinear elements and hierarchical design, advancing self-guided pathways for soft robotics and programmable materials.

Contribution

It presents a novel design framework for self-guided, multi-step shape-changing metamaterials using nonlinear mechanics and hierarchical architecture, enabling controlled reconfigurations without external actuation.

Findings

Demonstrated control of pathways via rational design of nonlinear elements.

Showed suppression of pathway errors through self-contacts.

Extended reconfiguration steps using hierarchical architectures.

Abstract

Multi-step pathways, constituted of a sequence of reconfigurations, are central to a wide variety of natural and man-made systems. Such pathways autonomously execute in self-guided processes such as protein folding and self-assembly, but require external control in macroscopic mechanical systems, provided by, e.g., actuators in robotics or manual folding in origami. Here we introduce shape-changing mechanical metamaterials, that exhibit self-guided multi-step pathways in response to global uniform compression. Their design combines strongly nonlinear mechanical elements with a multimodal architecture that allows for a sequence of topological reconfigurations, i.e., modifications of the topology caused by the formation of internal self-contacts. We realized such metamaterials by digital manufacturing, and show that the pathway and final configuration can be controlled by rational design of the nonlinear mechanical elements. We furthermore demonstrate that self-contacts suppress pathway errors. Finally, we demonstrate how hierarchical architectures allow to extend the number of distinct reconfiguration steps. Our work establishes general principles for designing mechanical pathways, opening new avenues for self-folding media, pluripotent materials, and pliable devices in, e.g., stretchable electronics and soft robotics.