In-Situ Self-Aligned NaCl-Solution Fluidic-Integrated Microwave Sensors for Industrial and Biomedical Applications

Abstract

This work presents, for the first time, an in-situ self-aligned fluidic-integrated microwave sensor for characterizing NaCl contents in NaCl-aqueous solution based on a 16-GHz bandpass combline cavity resonator. The discrimination of the NaCl concentration is achievable by determining amplitude differences and resonant frequency translations between the incident and reflected microwave signals at the input terminal of the cavity resonator based on the capacitive loading effects of the comb structure inside the cavity introduced by the NaCl solution under test. Twelve NaCl-aqueous liquid mixture samples with different NaCl concentrations ranging from 0% to 20% (0-200 mg/mL), which are generally exploited in most industrial and biomedical applications, were prepared and encapsulated inside a Teflon tube performing as a fluidic channel. The Teflon tube is subsequently inserted into the cavity resonator through two small holes, fabricated through the sidewalls of the cavity, which can be used to automatically align the fluidic subsystem inside the combline resonator considerably easing the sensor setup. Based on at least five repeated measurements, the NaCl sensor can discriminate the NaCl content of as low as 1% with the measurement accuracy of higher than 96% and the maximum standard deviation of only 0.0578. There are several significant advantages achieved by the novel NaCl sensors, e.g. high accuracy, traceability and repeatability; ease of sensor setup and integration to actual industrial and biomedical systems enabling insitu and real-time measurements; noninvasive and noncontaminative liquid solution characterization as well as superior sensor reusability due to a complete physical separation between the fluidic and microwave subsystems.

Visualization of microwave near-field distribution in sodium chloride and glucose aqueous solutions by a thermo-elastic optical indicator microscope

“…Sensitive single-target sensors with the ability to detect these compounds can reflect health status 25 . Among these compounds, for example, sensing NaCl concentrations in an aqueous solution can provide critical information regarding the water–salt balance in human tissues, hydration levels, and other health diagnoses 1 , 26 , 27 . Therefore, the design and fabrication of highly accurate and practice sensors is one of the challenging tasks in modern science.…”

Compact and Highly Sensitive Bended Microwave Liquid Sensor Based on a Metamaterial Complementary Split-Ring Resonator

“…Thanks to a detailed algebraic analysis, Equations ( 5) and (6) were generated [32]. Thus, the unknown coefficients can be determined as given in (7):…”

“…Microwave sensors are the current technological framework that has most attracted the attention of researchers in recent years. These sensors offer many advantages, including low manufacturing costs, high sensitivity, and high durability; these advantages make them very attractive and preferred choices in a variety of research fields, including biomedicine [7][8][9][10], chemistry [11][12][13], electronics, and industry [7,14,15]; they have even recently been used in food safety applications and mechanical systems [16][17][18].…”

An Integrated 3D-Printed Lens with Ultra-Wideband Flower-Shaped Stub Antenna for Ethanol-Water Mixture Characterization

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