TM02 Quarter-Mode Substrate-Integrated Waveguide Resonator for Dual Detection of Chemicals

Abstract

The detection of multiple fluids using a single chip has been attracting attention recently. A TM02 quarter-mode substrate-integrated waveguide resonator designed at 5.81 GHz on RT/duroid 6010LM with a return loss of 13 dB and an unloaded quality factor of Q ≈ 13 generates two distinct strong electric fields that can be manipulated to simultaneously detect two chemicals. Two asymmetric channels engraved in a polydimethylsiloxane sheet are loaded with analyte to produce a unique resonance frequency in each case, regardless of the dielectric constants of the liquids. Keeping in view the nature of lossy liquids such as ethanol, the initial structure and channels are optimized to ensure a reasonable return loss even in the case of loading lossy liquids. After loading the empty channels, Q is evaluated as 43. Ethanol (E) and deionized water (DI) are simultaneously loaded to demonstrate the detection of all possible combinations: [Air, Air], [E, DI], [DI, E], [E, E], and [DI, DI]. The proposed structure is miniaturized while exhibiting a performance comparable to that of existing multichannel microwave chemical sensors.

Low-Cost and Lightweight 3D-Printed Split-Ring Resonator for Chemical Sensing Applications

“…In addition, 3D printing, as an additive manufacturing technology, adds valuable features such as an etching-free and chemical-less processing. In [ 24 ] and [ 27 ], the structures were realized using photolithography, which is a subtractive manufacturing process. It requires various steps and a particularly clean environment and involves hazardous chemicals.…”

“…Q factors are estimated from S 21 curves (simulations and measurements) based on 3 dB bandwidth criterion such that Q = f r /Δ f 3dB [ 22 , 23 ]. Relative error in resonance frequency was estimated from the difference between the corresponding simulations and measurements [ 24 , 25 ].…”

Cylindrical Dielectric Resonator Antenna-Based Sensors for Liquid Chemical Detection

“…For this purpose, the loss tangent is kept at 0.4 which is the common value for ethanol at 3–5 GHz and the permittivity is varied. The average sensitivity [24] is determined using the following relation. Average0.277778emSensitivity0.277778em(S1)=0trueΔFΔϵ=8.750.277778emMHz/ϵr…”

Simplified Approach to Detect Dielectric Constant Using a Low-Cost Microfluidic Quarter Mode Substrate-Integrated Waveguide

“…Substrate-integrated waveguide structures maintain their radiation characteristics when they are miniaturized or split into equal portions. Figure 1 b shows that QMSIW cavity sides are not exact d/2, where d is the diameter of the original circular cavity, because fringe fields are generated from the QMSIW cavity open sides [ 29 ]. Hence, we add some small Δd to ensure the structure retains the same dominant mode as the full SIW cavity.…”

“…In References [ 13 ] and [ 14 ], they proposed a substrate-integrated waveguide (SIW) cavity to determine liquid complex permittivity and biomass. SIW and quarter-mode SIW (QMSIW) cavity resonators integrated with microfluidic technology have been subsequently used to detect biomaterial and dual chemicals [ 15 , 16 ]. Perturbation theory links mixture concentration and corresponding resonant frequency and QF changes.…”