High-Sensitivity Grooved CSRR-Based Sensor for Liquid Chemical Characterization

Abstract

In this work, a new complimentary split ring resonator (CSRR)-based sensor is proposed to sense chemical concentrations. A groove is created in the dielectric ring region of the CSRR to place the hollow tube containing the material under test (MUT). By placing the MUT in the region of high field concentration, higher sensitivity is achieved. The proposed novel and simple design alleviates the requirement of complex fluidic channels and space needed to place the MUT. The fabrication process is also simple with efficient utilization of the sensor’s sensitive region. The CSRR is excited uniquely through a transmission line with periodically placed capacitive gaps in series. By placing the capacitive gaps, effective negative permeability and permittivity are simultaneously achieved, and the structure exhibits metamaterial [composite right/left-handed transmission line (CRLH-TL)] left-handed behavior. Greater coupling of electromagnetic energy from the transmission line to the resonator is achieved by increasing the capacitive gap widths, which renders higher sensitivity. The main sensing parameter is the shift in the frequency of the transmission coefficient notch arising due to the placement of chemicals of varying concentrations throughout the ring region in the hollow tube. The sensor dimension is 4 cm (0.012 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda {g}$ </tex-math></inline-formula> ) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 4 cm (0.012 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda {g}$ </tex-math></inline-formula> ), with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda {g}$ </tex-math></inline-formula> being the guide wavelength. The large sensing bandwidth obtained is 1320 MHz that corresponds to high sensitivity of 14.66 MHz/unit change in concentration and 21.44 MHz/unit change in permittivity. The sensor is cheap and small, and the sensing process is simple offering instantaneous results.