1. Pennsylvania State University, Department of Engineering Science and Mechanics, NanoMM—Nanoengineered Metamaterials Group, 212 EES Building, University Park, Pennsylvania 16802, United States
2. Pennsylvania State University, Department of Engineering Science and Mechanics, NanoMM—Nanoengineered Metamaterials Group, 212 EES Building, University Park, Pennsylvania 16802, United StatesbUniversity of Edinburgh, School of Mathematics, Edinburgh EH9 3