Session: 12-28-01: Functional Soft Composites - Design, Mechanics, and Manufacturing

Paper Number: 146106

146106 - Magnetically Reconfigurable Conformal Metamaterials With Global Area-Preservation and Widely Tunable Physical Properties 

Metamaterials are architected materials that possess unique properties not observed in nature, which makes them promising candidates for a broad range of applications. Metamaterials consist of specifically designed periodic patterns, showing tailorable mechanical, acoustic, optical, or electromagnetic properties that are beneficial for diverse functions including noise control, vibration isolation, electromagnetic wave manipulation, cloaking, energy harvesting, etc. While traditional metamaterials exhibit fixed behaviors due to unchangeable material properties and geometries after fabrication, reconfigurable metamaterials, also called active metamaterials, alternatively possess actively tunable patterns and/or physical properties, facilitating more versatile and programmable use. For example, metamaterials relying on origami/kirigami folding and structural buckling have been developed, of which shape morphing and the coupled property reconfiguration are driven by manual handling, motors, or pumps, leading to bulky and tethered structures with restricted reliability, flexibility, and versatility.

Magnetically responsive metamaterials made of hard-magnetic soft active materials (a soft elastomer matrix embedded with hard magnetic particles), provide robust alternative strategies for reconfigurable metamaterials. These metamaterials show the advantages of selective, programmable, and reversible structural reconfiguration while possessing the merits of fast and untethered control under the applied magnetic field. We develop structurally reconfigurable metamaterials by constructing magnetically actuated planar lattices that can locally fold the unit cells for structure reconfiguration while globally morphing between flat and curved configurations as conformal and 3D freestanding metamaterials. The structurally reconfigurable metamaterial also serves as a medium for customizable subwavelength units by rationally designing attached conductive patterns for varied electromagnetic wave filtering performances such as narrow-band, dual-band, and wide-band filtering behaviors. To date, achieving area-preserving active metamaterials with distinct shape reconfigurations remains a prominent challenge. We further present a new metamaterial design strategy that can significantly change the area density while maintaining the overall area through a novel bilayer concept.  The bilayer metamaterials consist of two arrays of magnetic soft materials with distinct magnetization distributions. Under a magnetic field, each layer behaves differently, which allows the metamaterial to reconfigure its shape into multiple modes and to significantly tune its area density without changing its overall dimensions. The area-preserving multimodal shape reconfigurations are further exploited as active acoustic wave regulators to tune bandgaps and wave propagations. We anticipate that the demonstrated design strategies, controlled metamaterial reconfigurations, and dexterous manipulations of material physical properties, enable next-generation reconfigurable metamaterials in defense and aerospace applications with enhanced programmability and adaptability.

Lastly, we provide a voxel-encoding direct ink writing printing method to program both the magnetic density and direction of hard-magnetic soft active materials. To design the property distribution, an evolutionary algorithm (EA)-based design strategy is utilized to achieve the desired magnetic actuation. With the new EA-guided voxel-encoding printing technique, we demonstrate the functional magnetic actuation that produces complicated shape morphing, which can be utilized for future magnetic metamaterial designs with desired reconfigurabilities and physical properties.

Presenting Author: Shuai Wu Stanford University

Presenting Author Biography: Shuai Wu is currently a PhD candidate in Professor Renee Zhao's group in Mechanical Engineering at Stanford University. His research focuses on the mechanics-guided design of functional soft composite, soft robotics, and active metamaterials.

Authors:

Shuai Wu Stanford University
Jay Sim Stanford University
Ruike Renee Zhao Stanford University