| Planar microwave sensors are capturing widespread attention regarding high sensitivity,selectivity,non-contact sensing,and device miniaturization.The inherent trade-off between sensitivity,linearity,and selectivity related to these sensors renders its challenging to enhance the performance of planar microwave sensors.Furthermore,the enormous requirement for non-invasive and real-time measurement of solid and gas-type sensors has prompted considerable research into developing efficient techniques for enhancing microwave non-contact sensor’s sensitivity,selectivity,and Q-factor.This research suggests an interdigital structure-based planar microwave resonant sensor using parametric optimization,off-resonator coupling,and high-porosity 2D nanomaterial-based impedance matching strategies to enhance the sensitivity and selectivity of microwave resonant sensors.The trade-off interaction between technical specifications is explored systematically,evaluated numerically,and a mechanism for distributing electromagnetic energy is presented to maximize their values.The developed planar microwave sensors are used for the sensitive and accurate detection of multidimensional assessment of material characterization,non-contact single/multilayer measurement of magneto-dielectric material,and detection of volatile organic compounds under the humidity variant environment.The results of this study have significant implications for improving the sensitivity and selectivity issue for non-invasive and real-time measurement of solid and gas sensors at room temperature,thereby offering innovative ideas for integrating microwave sensors in evolving interdisciplinary fields.The following are the main innovative points demonstrated in this research work:First of all,a parallel interdigital capacitance structure is designed to produce a high electric field distribution at two different resonant frequencies(2.3 GHz and 5.7 GHz)for the sensitive multidimensional assessment of material characterization.However,microwave sensing techniques often face challenges in accurately measuring multidimensional characterization simultaneously,especially when dealing with complex permittivity of a sample close to a vacuum.The developed microwave sensor configured as a spur-line structure generates a high-intensity coupled resonating E-field suitable for sensitive measurement of the complex permittivity(276MHz/Δε_r)and solid material thickness(143 MHz/mm).Secondly,a high electric and magnetic field interdigitated resonator structure is proposed in horizontal(fingers)and vertical(electrodes)directions to achieve high sensitivity for detecting a sample’s complex permittivity,complex permeability and thicknesses.However,the active microwave sensors employ an active component to attain a high Q-factor,but it becomes challenging concerned to the cost and complexity of the design.This innovation fills the gap in microwave-based non-contact sensing and single/multilayer measurement applications with high Q-factor.The resonance frequency at 5.9 GHz of the designed sensor exhibited high sensitivities(324 MHz/Δε_r and 825 MHz/Δμ_r)for characterizing magneto-dielectric materials,with a high Q-factor(1700).Finally,a microwave-based interdigital structure with an MXene sensitive interface layer is developed to produce a high electric field distribution for the ppm-level high sensitivity.This innovation point is significant because it fills the gap in microwave-based VOC gas non-contact sensing applications with enhanced sensitivity.However,conventional sensing techniques often face limitations regarding sensitivity and non-contact measurements of these gases.This innovation opens up new possibilities for enhanced sensitivity and non-contact measurements.The designed microwave gas sensor achieved a linear coefficient between the resonance frequency(4.0GHz)and the low concentration of acetone gas(1-500 ppm)under the humidity(10-90%RH)variant environment,with the sensitivity reaching 17.85 kHz/ppm. |
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