Guided transition waves in multistable mechanical metamaterials

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 117; no. 5; pp. 2319 - 2325
• Main Authors: Jin, Lishuai, Khajehtourian, Romik, Mueller, Jochen, Rafsanjani, Ahmad, Tournat, Vincent, Bertoldi, Katia, Kochmann, Dennis M.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 04.02.2020
• Subjects: Acoustics; Computational fluid dynamics; Crystal defects; Energy absorption; Engineering Sciences; Free surfaces; Geophysics; Mechanics; Metamaterials; Morphing; Nonlinear Sciences; Pattern Formation and Solitons; Phase transitions; Physical Sciences; Physics; Point defects; Robotics; Stiffness; Two dimensional models; Vibrations; mechanical metamaterial; multistability; nonlinear dynamics; structure; phase transformation
• DOI: 10.1073/pnas.1913228117
• ISSN: 0027-8424

Transition fronts, moving through solids and fluids in the form of propagating domain or phase boundaries, have recently been mimicked at the structural level in bistable architectures. What has been limited to simple one-dimensional (1D) examples is here cast into a blueprint for higher dimensions, demonstrated through 2D experiments and described by a continuum mechanical model that draws inspiration from phase transition theory in crystalline solids. Unlike materials, the presented structural analogs admit precise control of the transition wave’s direction, shape, and velocity through spatially tailoring the underlying periodic network architecture (locally varying the shape or stiffness of the fundamental building blocks, and exploiting interactions of transition fronts with lattice defects such as point defects and free surfaces). The outcome is a predictable and programmable strongly nonlinear metamaterial motion with potential for, for example, propulsion in soft robotics, morphing surfaces, reconfigurable devices, mechanical logic, and controlled energy absorption.