Highly Sensitive Permittivity Sensor Using an Inhomogeneous Metamaterial Cylindrical Waveguide

Cylindrical waveguides filled with anisotropic metamaterials enable novel wave propagation phenomena. A nanoporous alumina microtube is a manifestation of such an anisotropicwaveguidewith an effective permittivity tensor (epsilon(r) not equal epsilon(phi) = epsilon(z)). The metamaterial would be considered to be filled homogeneously or inhomogeneously depending on the variation of the size of the nanopores and density of the nanopores. The electromagnetic fields in such metamaterial waveguide are highly sensitive to the refractive index of the material embedded in the nanopores and the variation of the density of the inclusion in the radial direction due to themodal field distributions. We show that there is a large variation in the reflection coefficient (S-11) of the inhomogeneously filled nanoporouswaveguidewith an embedded liquidwith small variations in thematerial properties of the liquid. This variation in the S-11 parameter can use to determine the purity of liquid. Our results show that the permittivity variations of the inclusion material can be monitored up to the sixth decimal places theoretically. The analysis also indicates that the inhomogeneous metamaterial waveguide is more sensitive compared to both the homogeneously filled metamaterial waveguide and an isotropic waveguide covered with metamaterial clad. This waveguide has potential applications in biomedical and chemical sensing applications.

Automated summary

Cylindrical waveguides filled with anisotropic metamaterials enable novel wave propagation phenomena, and variations in the reflection coefficient of the inhomogeneously filled waveguide can be used for detecting liquid purity, with potential for ultra-precise monitoring of permittivity variations of inclusion materials. These findings suggest that inhomogeneous metamaterial waveguides are more sensitive compared to homogeneous ones, with potential applications in biomedical and chemical sensing.