Microwave microfluidic sensor based on microstrip-line-coupled complementary resonator

This paper presents a microwave microfluidic sensor based on a complementary electric-LC resonator loaded on a microstrip line. By flowing water-ethanol solutions with different water volume fractions, the resonance frequency and the notch depth in the transmission response of the sensor are modified. These changes are used for determining the complex permittivity of the solution. A sensor prototype has been fabricated and measurements are used for verification of the sensing principle.