NASA Langley Research Center has developed a novel negative dielectric constant material based on ion-conducting materials. A negative dielectric constant material is an essential key for creating metamaterials, or artificial negative index materials (NIMs). NIMs have generated great attention due to their unique and exotic electromagnetic properties, and could be used for unique optical and microwave applications, including new methods of electromagnetic cloaking and extremely lowloss communications.
Metamaterials or artificial NIMs are specially designed to exhibit a negative index of refraction, which is a property not found in any known naturally occurring material. These artificially configured composites have a potential to fill voids in the electromagnetic spectrum where conventional material cannot access a response, and enable the construction of novel devices such as microwave circuits and antenna components. The negative effective dielectric constant is a very important key for creating materials with a negative refractive index. However, current methods to achieve a negative effective dielectric constant are difficult to produce, not readily applicable to producing commercial metamaterials, and can have limited tunabilty.
This invention is for a novel method to produce a material with a negative dielectric constant by doping ions into polymers, such as with a protonated poly(benzimidazole) (PBI), without complex geometric structures. The doped PBI shows a negative dielectric constant at megahertz (MHz) frequencies due to its reduced plasma frequency and an induction effect. The magnitude of the negative dielectric constant and the resonance frequency are tunable by dopant type and doping concentration.