Relative Permittivity Measurement of Microliter Volume Liquid Samples through Microwave Filters

This paper proposes a concept of dielectric characterization of low-volume liquid samples using the coupling coefficient of filters. The concept is validated through a two-pole substrate integrated waveguide filter in which the liquid under test is mounted on the coupling section between the two res...

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Bibliographic Details
Published in:Sensors (Basel, Switzerland) Switzerland), 2023-03, Vol.23 (6), p.2884
Main Authors: Yasin, Azhar, Gogosh, Nayab, Sohail, Syed Irfan, Abbas, Syed Muzahir, Shafique, Muhammad Farhan, Mahmoud, Abdelhady
Format: Article
Language:English
Subjects:
Alcohols
Analysis
Capillary tubes
Coupling coefficients
dielectric liquids
dielectric measurements
Dielectric properties
Electric filters
Electromagnetic wave filters
Error analysis
Ethanol
Glucose
Investigations
Measurement
Microwave filters
Permittivity
Perturbation methods
Resonators
Sensors
Substrate integrated waveguides
substrate-integrated waveguides (SIW)
Waveguide filters
Waveguides
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Summary:This paper proposes a concept of dielectric characterization of low-volume liquid samples using the coupling coefficient of filters. The concept is validated through a two-pole substrate integrated waveguide filter in which the liquid under test is mounted on the coupling section between the two resonators. Unlike the conventional resonator perturbation method reported many times in the literature, this technique uses the coupling coefficient for sensing. The liquid sample is collected in a capillary tube and carefully positioned on the coupling section of the filter; the coupling coefficient of the two resonators varies compared to the relative permittivity of the sample; thus, an empirical model is established. The proposed sensor has been tested to compute the permittivity of different alcohols. Binary solutions of ethanol and water have also been characterized to calculate the volume ratio and relative permittivity as a proof-of-concept. The obtained results show that the proposed sensing technique is capable of characterizing a low quantity of liquids (≈44 µL) with good accuracy, and a worst case measured error of only 6.8% is noted. The ease of integration with other circuitry, low cost, reusability with no deterioration, and adaptability of the proposed sensor makes it a suitable choice for the chemical as well as for the pharmaceutical industry.
ISSN:1424-8220
1424-8220
DOI:10.3390/s23062884