| Metamaterials have gained significant attention over the last decade because they can exhibit electromagnetic properties that are not readily available in naturally occurring materials. This dissertation describes our work on design, fabrication and characterization of liquid metal-based metamaterials with focus on their applications in the terahertz (THz) frequency range. In contrast to the more conventional approaches to fabricating these structures, which rely on vacuum deposited solid metal films, we used metals that are liquid at room temperature. This family of materials is especially attractive for such applications, since it enables large-scale reconfigurability in the overall geometry of the device. We demonstrate a number of unique plasmonic and metamaterial devices. Within the topic of plasmonics, we demonstrate a device that allows for mechanical stretching that is reversibly deformable. In an analogous structure, we can change the geometry dramatically by injecting or withdrawing liquid metals from specific area of the pattern. We also developed a liquid metal-based reconfigurable THz metamaterial device that is not only pressure driven, but also exhibits pressure memory. As an alternate approach to demonstrate reconfigurability, we developed a technique for creating dramatic configuration changes in a device via selective erasure and refilling of metamaterial unit cells that utilizes hydrochloric acid. While the approach is successful in changing the geometry, it does not allow for fine spatial control of the pattern. Thus, we have refined the approach by developing an electrolytic process to change the geometry of a liquid metal-based structured device in a more localized and controlled manner. Since liquid metals can be solidified under certain conditions, we have demonstrated a novel technique for fabrication of free-standing two-dimensional and three-dimensional terahertz metamaterial devices using injection molding of gallium. Finally, we developed a technique of printing three-dimensional solid metal structures by pulling liquid gallium out of a reservoir via solid/liquid interface. Based on these results, we are currently extending our work towards development of metamaterials that can be used in real-world applications. Based on the significant progress made the THz field over the last two decades, the likelihood of THz systems level applications is much brighter. |
