Edge-selective reconfiguration in polarized lattices with magnet-enabled bistability

• Published in: Extreme Mechanics Letters Vol. 71; p. 102217
• Main Authors: Iorio, Luca, Ardito, Raffaele, Gonella, Stefano
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2024
• Subjects: Bistability; Soft metamaterials; Topological matter; Soft metamaterials; Topological matter; Bistability
• ISSN: 2352-4316; 2352-4316
• DOI: 10.1016/j.eml.2024.102217

The signature topological feature of Maxwell lattices is their polarization, which manifests as an unbalance in stiffness between opposite edges of a finite domain. The manifestation of this asymmetry is especially dramatic in the case of soft lattices undergoing large nonlinear deformation under concentrated loads, where the excess of softness at the soft edge can result in the activation of sharp indentations. This study explores how this mechanical dichotomy between edges can be tuned and possibly extremized by working with soft magneto-mechanical metamaterials. The magneto-mechanical coupling is obtained by endowing the lattice sites with permanent magnets, which activate a network of magnetic forces that can interact with – either augmenting or competing with – the elasticity of the material. Specifically, under sufficiently large deformation that macroscopically alters the equilibrium positions of the sites, the attractive forces between the magnets can trigger bistable reconfiguration mechanisms. The strength of such mechanisms depends on the landscapes of elastic reaction forces exhibited by the edges, which are different due to the polarization, and is therefore inherently edge-selective. We show that, on the soft edge, the addition of magnets simply enhances the softness of the edge. In contrast, on the stiff edge, the magnets activate snapping mechanisms that locally reconfigure the cells and produce a lattice response reminiscent of plasticity, characterized by residual deformation that persists upon unloading. •This work reveals the extraordinarily diverse landscape of deformation regimes emerging from the cooperative interplay between polarization and bistability in soft magneto-mechanical lattices.•It introduces a new paradigm by shifting focus from conventional approaches, where polarization is typically studied in the linear regime, to exploring the large deformation regimes of soft media and the multi-physical effects of elasto-magnetic interactions.•The use of magnets enables shape-reconfiguring mechanisms, and the interplay between polarization and instabilities intensifies the edge dichotomy, leading to a fascinating proliferation of edge-selective scenarios.