A Sensor for Characterisation of Liquid Materials with High Permittivity and High Dielectric Loss

Abstract

This paper reports on a sensor based on multi-element complementary split-ring resonator for the measurement of liquid materials. The resonator consists of three split rings for improved measurement sensitivity. A hole is fabricated at the centre of the rings to accommodate a hollow glass tube, through which the liquid sample can be injected. Electromagnetic simulations demonstrate that both the resonant frequency and quality factor of the sensor vary considerably with the dielectric constant and loss tangent of the liquid sample. The volume ratio between the liquid sample and glass tube is 0.36, yielding great sensitivity in the measured results for high loss liquids. Compared to the design based on rectangular split rings, the proposed ring structure offers 37% larger frequency shifts and 9.1% greater resonant dips. The relationship between dielectric constant, loss tangent, measured quality factor and resonant frequency is derived. Experimental verification is conducted using ethanol solution with different concentrations. The measurement accuracy is calculated to be within 2.8%, and this validates the proposed approach.

Planar Microwave Sensor with High Sensitivity for Material Characterization Based on Square Split Ring Resonator (SSRR) for Solid and Liquid

“…The split-ring resonator calculation is used to predict the geometric structure in the beginning stages of the sensor design by using equations (1)-(3) [25,26]. A microwave microstrip resonator and a planar ring resonator make up the sensor architecture.…”

Highly Sensitive Microwave Sensors Based on Open Complementary Square Split-Ring Resonator for Sensing Liquid Materials

“…Numerous microwave sensors have been developed to characterize various materials, including oils [ 5 , 6 , 7 ], coal [ 8 , 9 ], glucose [ 10 , 11 , 12 ], solids [ 13 , 14 , 15 ], gases [ 16 , 17 , 18 ], and gesomin [ 19 ]. In particular, microwave sensors are also widely used for detecting liquid samples (such as ethanol) based on the glass tube method [ 20 , 21 ], LC method [ 22 ], or microfluidic channel method [ 23 , 24 ]. From the results in the literature, it is found that the microfluidic channel method leads to the highest sensitivity of up to 268 MHz/RIU compared to other methods.…”

“…The main sensing element of these microwave sensors are resonator-based as it offers several advantages like simple design, high performance characteristics, low cost, and ease of fabrication. For example, the split-ring resonator [ 26 ], complementary split-ring resonators (CSRR) [ 21 ], substrate-integrated waveguide resonator [ 25 ], Minkowski-like fractal resonator [ 31 ], complementary circular spiral resonator [ 28 ], gap waveguide cavity resonator [ 27 ], multiple split-ring resonator [ 33 ] and, multiple complementary split-ring resonator [ 29 ], which are coupled to a transmission line, have gained considerable attention for potential sensing applications with various liquid samples. Microwave sensors based on conventional complementary split-ring resonators have achieved a sensitivity of 268 MHz/RIU [ 24 ].…”

Ultrasensitive miniaturized planar microwave sensor for characterization of water–alcohol mixtures

“…Complementary SRRs (CSRR) which are the negative image of SRRs, have also been thoroughly investigated 19 – 22 . Javed et al 19 and then Wang et al 20 followed a similar approach to characterize complex permittivities of water–ethanol solutions. Their designs were based on multiple CSRRs, consisting of a defected ground structure with multiple interconnected rings, which are excited by a microstrip line on the opposite side of the substrate.…”