Single Whispering-Gallery-Mode Resonator With Microfluidic Chip as a Basis for Multifrequency Microwave Permittivity Measurement of Liquids

TL;DR

This paper introduces a multifrequency microwave measurement technique using a whispering-gallery-mode resonator with a microfluidic chip to accurately determine the complex permittivity of small liquid samples across multiple frequencies.

Contribution

It presents a novel method combining a single WGM resonator and microfluidics for multifrequency permittivity measurement, enabling detailed liquid property analysis.

Findings

Measured complex permittivity of liquids at six frequencies between 30-40 GHz.

Demonstrated the technique on L-lysine in water solutions.

Showed potential for biological liquid analysis and small volume dielectric studies.

Abstract

The accurate measurement of complex liquid permittivity in a frequency range provides important information on liquid properties in comparison to single frequency permittivity investigations. The multifrequency microwave characterization technique based on a single quartz whispering-gallery-mode (WGM) resonator with a microfluidic chip are proposed, developed, and demonstrated. This technique allows the complex permittivity of small volumes of liquid to be measured at six resonant frequencies in the 30-40 GHz frequency range. The calibration is performed by simulating the measurement cell and by plotting the calibration nomogram charts for all six investigated frequencies. The novel approach is applied in studies of the complex permittivity of the L-lysine in water solutions. The results open up possibilities to investigate the complex permittivity of biological liquids at several frequencies and to further develop the microwave dielectrometry of small liquid volumes in a certain frequency range using the quasi-optical nature of a single high-Q WGM resonator.