Innovative Synthesis of Auxetic Metamaterials with Enhanced Energy Absorption Using Liquid Crystal Elastomers

This work presents a novel method for synthesizing auxetic liquid crystal elastomer (LCE) foam, a metamaterial with the potential to revolutionize energy absorption. Auxetic structures, characterized by their negative Poisson's ratio (expansion upon compression), are known for their exceptional energy dissipation capabilities. Liquid crystal elastomers (LCEs) possess another intuitive property for energy dissipation: their rigid liquid crystal molecules can reorient under stress. By combining these two remarkable properties, we propose a novel approach to create a material with extraordinary impact absorption features. This approach utilizes a foaming agent, cyclopentane, for the first time ever to create a porous LCE base structure. We are not aware of any research that has developed a foaming agent of LCE. This novel foaming agent method offers a simpler approach to fabricate LCE foams, avoiding the need for time-consuming and complex methods like salt leaching, nickel etching, or 3D printing. Then, this LCE foam is transformed into an auxetic foam through a combined pressure and heat treatment. This method takes advantage of the synergistic energy dissipation mechanisms of auxetic structures and LCEs, potentially leading to a new class of metamaterial with significantly enhanced energy absorption characteristics. Such metamaterials could find applications in various fields, including impact protection in sports equipment, vibration damping for noise reduction, and energy harvesting devices.