Broadband resonant calibration-free complex permittivity retrieval of liquid solutions

TL;DR

This paper introduces a calibration-free, broadband method for measuring the complex permittivity of liquids and solids using magnetic dipole resonance in spherical samples, simplifying and broadening material characterization.

Contribution

A novel calibration-free technique combining resonant and non-resonant methods for broadband permittivity retrieval across liquids and solids.

Findings

Effective in liquids with loss tangent < 0.5

Uses size-dependent magnetic dipole resonance

Applicable to powders and solids

Abstract

Material susceptibilities govern interactions between electromagnetic waves and matter and are of a crucial importance for basic understanding of natural phenomena and for tailoring practical applications. Here we present a new calibration-free method for relative complex permittivity retrieval, which allows using accessible and cheap apparatus and simplifies the measurement process. The method combines advantages of resonant and non-resonant techniques, allowing to extract parameters of liquids and solids in a broad frequency range, where material's loss tangent is less than 0.5. The essence of the method is based on exciting magnetic dipole resonance in a spherical sample with variable dimensions. Size-dependent resonant frequencies and quality factors of magnetic dipolar modes are mapped on real and imaginary parts of permittivity by employing Mie theory. Samples are comprised of liquid solutions, enclosed in stretchable covers, which allows changing the dimensions continuously. This approach allows tuning magnetic dipolar resonance over a wide frequency range, effectively making resonance retrieval method broadband. The technique can be extended to powder and solid materials, depending on their physical parameters, such as granularity and processability.