Sensitivity enhancement of split ring resonator based liquid sensors

Chemical Gas Sensor Based on a Flexible Capacitive Microwave Transducer Associated with a Sensitive Carbon Composite Polymer Film

“…The 0 ppm concentration corresponds to nitrogen exposure only. The relative permittivity of the ethanol is about 24.5 at 25 °C, compared to the permittivity of nitrogen which is close to 1, that may cause a change in the environment of the sensor and will thus modify the electrical properties of the sensitive layer, resulting in an additional variation of the sensing channel compared to the reference one [9]. All detections are carried out under the same conditions, at a fixed temperature equal to 26 °C and a humidity of 32% RH.…”

Planar Microwave Resonant Sensors: A Review and Recent Developments

“…The typical, although not exclusive, configuration of such sensors is a transmission line loaded with the resonant element (either in contact or coupled to it), see Figure 1a. Although examples of frequency variation sensors devoted to the measurement of spatial variables have been reported [15], typically these sensors have been applied to dielectric characterization of solids and liquids [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46], as far as the resonance frequency and quality factor depend on the complex dielectric constant of the surrounding material (the so-called material under test (MUT)). These sensors are very simple, but they are potentially subjected to cross-sensitivities caused by variations in ambient factors, such as temperature and humidity, and therefore they need calibration before their use.…”

Chemical gas sensor based on a novel capacitive microwave flexible transducer and composite polymer carbon nanomaterials

“…On each sensitive channel of both devices, we have simulated the presence of 5 to 50 layers of PEDOT: PSS [7], which have similar properties as the PEDOT: PSS -MWCNTs sensitive material used in this study, due to very low concentration of MWCNT. Full simulations were carried out for the first resonant mode with 10 and 5 sensitive layers respectively for D1 and D2 in order to study the influence of a permittivity variation modeling the absorption of vapor compounds [8]. The results, represented on FIG.…”

“…Ethanol was used as the target vapor, using the sequence: 0, 500, 0, 500, 0, 1000, 0, 1000, 0 and 2000 ppm for 10 minutes each concentration step, carried out after an initial rinsing step under nitrogen for 450 min to ensure stability at room temperature. The relative permittivity of the ethanol is about 24.5 at 25°C, which will cause a change in the environment of the sensor with respect to the permittivity of nitrogen close to 1 and will modify the electrical properties of the sensitive layer [8]. All detections are carried out with the same conditions, at a fixed temperature equal to 26°C and a humidity of 32% RH.…”