Complex Permittivity Characterization of Liquid Samples Based on a Split Ring Resonator (SRR).

Jialu Ma,Lianghao Guo,Yubin Gong,Shaomeng Wang,Kaicheng Wang,Jingchao Tang

doi:10.3390/s21103385

Jialu Ma, Lianghao Guo + Show 4 more

Open Access

https://doi.org/10.3390/s21103385

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Abstract

A complex permittivity characterization method for liquid samples has been proposed. The measurement is carried out based on a self-designed microwave sensor with a split ring resonator (SRR), the unload resonant frequency of which is 5.05 GHz. The liquid samples in capillary are placed in the resonant zone of the fabricated senor for high sensitivity measurement. The frequency shift of 58.7 MHz is achieved when the capillary is filled with ethanol, corresponding a sensitivity of 97.46 MHz/μL. The complex permittivity of methanol, ethanol, isopropanol (IPA) and deionized water at the resonant frequency are measured and calibrated by the first order Debye model. Then, the complex permittivity of different concentrations of aqueous solutions of these materials are measured by using the calibrated sensor system. The results show that the proposed sensor has high sensitivity and accuracy in measuring the complex permittivity of liquid samples with volumes as small as 0.13 μL. It provides a useful reference for the complex permittivity characterization of small amount of liquid chemical samples. In addition, the characterization of an important biological sample (inositol) is carried out by using the proposed sensor.

Highlights

Over the past decades, material characterization in the microwave/RF range, owing to the great potential application in many areas such as biomedical, chemical, food safety and agriculture fields [1,2,3,4] has been attracting more and more interest
Because the sensor area is in the concentrated electromagnetic field, which means the material under test (MUT) can cause larger perturbation of the electromagnetic field
A sensor based on split ring resonator (SRR) used for the complex permittivity characterization of liquid samples has been proposed in the microwave frequencies range

Summary

Introduction

Material characterization in the microwave/RF range, owing to the great potential application in many areas such as biomedical, chemical, food safety and agriculture fields [1,2,3,4] has been attracting more and more interest. The non-resonant methods such as free space methods and transmission/reflection methods provide performing measurements for a great amount of material in large bandwidth, but the measurement accuracy and sensitivity are not precise enough. Chretiennot et al [25] presented a novel planar resonance structure based on microfluidic technology to achieve the sensing of liquid samples. Microwave sensor based on SRR have been widely used in the sensing field for the advantage of lower cost, less samples, and higher sensitivity. An improved microwave sensor based on planar SRR with a resonant frequency of 5.05 GHz is proposed and fabricated, its sensitivity for small volume liquid samples has been investigated. The manuscript is organized as follows: In Section 2, the proposed microwave sensor based on resonant perturbation method for the material characterization is discussed in details.

Sensor Design

Sensor’s Characteristic

Complex Permittivity Characterization of Inositol Solution

Conclusions