Microwave Microfluidic Sensor Based on a Microstrip Splitter/Combiner Configuration and Split Ring Resonators (SRRs) for Dielectric Characterization of Liquids

A microwave microfluidic sensor for dielectric characterization of liquids in real time is presented in this paper. The sensor is implemented in microstrip technology and consists of a symmetric splitter/combiner configuration loaded with a pair of identical split ring resonators (SRRs) and microflu...

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Bibliographic Details
Published in:IEEE sensors journal 2017-10, Vol.17 (20), p.6589-6598
Main Authors: Velez, Paris, Lijuan Su, Grenier, Katia, Mata-Contreras, Javier, Dubuc, David, Martin, Ferran
Format: Article
Language:English
Subjects:
dielectric characterization of liquids
differential sensors
Electromagnetism
Engineering Sciences
Micro and nanotechnologies
Microelectronics
Microfluidics
microstrip technology
Microwave circuits
Microwave sensors
permittivity measurements
Resonant frequency
Resonators
Sensor phenomena and characterization
split ring resonator (SRR)
Transmission line measurements
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Summary:A microwave microfluidic sensor for dielectric characterization of liquids in real time is presented in this paper. The sensor is implemented in microstrip technology and consists of a symmetric splitter/combiner configuration loaded with a pair of identical split ring resonators (SRRs) and microfluidic channels placed on top of them (gap region). The sensor works in differential mode and sensing is based on frequency splitting. Thus, if the structure is unloaded or if it is symmetrically loaded with regard to the axial plane, only one transmission zero (notch) in the frequency response appears. However, if the axial symmetry is disrupted (e.g., by the presence of different liquids in the channels), two transmission zeros arise, and the difference in magnitude (notch depth) and frequency between such transmission zeros is indicative of the difference in the dielectric properties (complex dielectric constant). A circuit schematic, including transmission line sections to describe the distributed components, lumped elements to account for the SRRs and their coupling to the lines and lumped elements to model the liquid properties, is presented and validated. After proper calibration, the functionality of the proposed sensor is demonstrated by measuring the complex permittivity in solutions of deionized water and ethanol as a function of the ethanol content.
ISSN:1530-437X
1558-1748
DOI:10.1109/JSEN.2017.2747764