Design of High-Sensitivity Microfluidic Sensor Based on CSRR With Interdigital Structure

In this article, a highly sensitive microwave microfluidic sensor for measuring the complex dielectric constant of liquid samples is proposed. The proposed sensor is based on a triple complementary split ring resonator loaded with interdigital electrodes (TCSRR-IDEs). The proposed sensor adopts an annular structure composed of interdigital electrodes (IDEs) in the middle ring, so as to further improve the field confinement and obtain the highest electric field strength. The outer ring is optimized to further enhance the performance of the sensor. A specimen container made of acrylonitrile-butadiene-styrene (ABS) plastic placed on the middle and outer rings with high electric field strength is employed to inject different solutions under test. The complex dielectric constant of the liquid sample is calculated by using the variations of resonance frequency and peak attenuation. The proposed sensor resonates at 2.64 GHz with a maximum frequency offset of 1030 MHz. In addition, the measurement error of the real part of the complex permittivity of this sensor is 2.8%, and the measurement error of the imaginary part is 8%. The measured results are consistent with the simulation consequences. Compared with the previous similar works, the sensor is small in size and has an average sensitivity of 1.23%.