A 20-GHz Microwave Miniaturized Ring Resonator for nL Microfluidic Sensing Applications

• Published in: IEEE sensors letters Vol. 3; no. 6; pp. 1 - 4
• Main Authors: Bao, Juncheng, Yan, Sen, Markovic, Tomislav, Ocket, Ilja, Kil, Dries, Brancato, Luigi, Puers, Robert, Nauwelaers, Bart
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01-06-2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: biosensors; Capacitive sensors; Capacitors; Change detection; Chemical and biological sensors; Coplanar waveguides; Deionization; Detection; Flow cytometry; Liquids; microfabrication; Microfluidics; microwave sensors; Permittivity; Resonators; Spatial resolution; Transmission line measurements
• ISSN: 2475-1472; 2475-1472
• DOI: 10.1109/LSENS.2019.2916466

In this article, a miniaturized microwave resonator is designed and fabricated. A loop-mode resonance is created when the permittivity difference between the two materials loaded in the two fluidic channels is sufficiently large. A highly concentrated electrical field is generated in a microfluidic channel loaded with deionized water to achieve high sensing spatial resolution within a sensing volume of 45 pL. On-wafer measurements are performed by keeping one channel unloaded as a reference while loading the other channel with different mixtures of isopropanol and deionized water. The acquired microwave-microfluidic measurements confirm that the proposed resonator can detect changes in the permittivity of the loaded liquid between the values of 3.2 and 42.4, making it a promising low-cost and label-free approach in applications requiring novel sensing techniques such as mixing monitoring and flow cytometry.