Novel technique for three-dimensional isotropic metamaterial fabrication.

We present a novel technique to fabricate 3D isotropic metamaterials (MTMs) with a low-cost and simple technique. There have been many techniques to fabricate 3D metamaterials such as Low-Pressure Chemical Vapor Deposition (LPCVD) and strain mismatch, Focused ion-beam milling, Lithography and etc. However, it is very difficult to fabricate 3D isotropic metamaterials with these methods because of the complexity of the 3D isotropic structures. Also MTMs fabricated by these methods are designed and fabricated on Silicon wafers or printed circuit boards. In our work, we develop a new technique using printing and casting methods to fabricate 3D flexible Isotropic MTMs for various applications. This technique can extend the MTM's lifetime and make it practical for outdoor use and conformation. The fabrication methodology for MTMs utilizes a low-cost and convenient screen printing technique. These MTMs are fully conformable and are fabricated using silver compounds deposited on Polyester sheets. Then, these MTM sheets are organized to form 3D isotropic structures, and are cast in Silicone rubber at room temperature for 24 hours to protect them from harsh environments. In order to obtain the aforementioned 3D isotropic MTM design, the Finite-Difference Time-Domain (FDTD) method is applied as a simulation tool. This tool is also used for validation of experimental results. The proposed technique can be used to fabricate not only 3D flexible isotropic metamaterials but also flexible metamaterial substrates with various material properties for applications in flexible band-stop filters and conformal patch antennas. It was shown that MTM-based patch antennas outperformed their non-MTM based counterparts in terms of losses and miniaturization. Moreover, the strain testing on these flexible devices showed a linear response with respect to strain applied and resonant frequency and show promise for applications as strain sensors. The results of novel fabrication technique and the computational and experimental analysis of our MTM substrates and microwave applications are presented in this work. Moreover, several parametric studies on the conductivity of the materials used for fabrication, linewidth reduction, as well as weight reduction of the MTMs are also conducted.