Fully Automated Electrically Controlled Tunable Broadband Interferometric Dielectric Spectroscopy for Aqueous Solutions

Abstract

A fully automated electrically controlled tunable interference based microwave sensor is demonstrated with broadband complex permittivity measurements of aqueous-solutions within the frequency range of 12-18 GHz. To construct deep destructive interference over the above-mentioned bandwidth, two Quadrature Hybrids (QH or 90 o coupler) split and combine the signals of Material-Under-Test (MUT) channel and Reference (REF) channel with 180 o phase shift. Together with voltage variable Phase Shifters (PS) and attenuators in both channels, the destructive interference nulls of the desired frequency can be easily tuned have a Q-factor of 2.67 × 10 3 . Coplanar waveguide (CPW) sensor design was used as the microwave sensing structure and closed microfluidic channel was designed and manufactured with polydimethylsiloxane (PDMS) to facilitate the alteration of MUT, REF and calibration liquids. Benefiting from electrically controlled PS and attenuator, the measurement system is fully automated for accurate and fast broadband microwave liquid characterization. Measurement of 2-propanol-water solutions (IPA solutions) with volume concentration of 1% is performed to illustrate automation processes and its high sensitivity. Mathematical model modified from those in literature was applied to extract MUT permittivity, which addresses improvements in accuracy, sensitivity and effective MUT volume compared to state-of-art sensors, with an average relative error (ARE) of 0.824% for the effective volume of 5.18 µl. The complex permittivity of 2-propanol-water solutions with different mole fractions were obtained, then confirmed with current literature data.

Design and Development of Zirconia-Alumina Bioceramics Obtained at Low Temperature through Eco-Friendly Technology

“…The microwave sintering conditions have been 1300°C of maximum temperature during 10 min of dwell time and 50°C/min of a heating rate. It is worthy of being mentioned that the zirconia-alumina composites are poorly microwave-absorbent materials at low temperatures, since its dielectric loss factor at room temperature is less than 0.01 [28]. This fact makes hybrid heating necessary, using silicon carbide as a susceptor [29,30].…”

Integrated liquid–liquid percentage determination microwave sensor exploiting single‐frequency transmission amplitude measurement technique

“…One of the frequent applications of microwave sensors is the aqueous solution characterization 7–11 . Many different measurement techniques have already been investigated to determine the liquid–liquid mixture percentage.…”

“…One of the frequent applications of microwave sensors is the aqueous solution characterization. [7][8][9][10][11] Many different measurement techniques have already been investigated to determine the liquid-liquid mixture percentage. Nevertheless, the single-frequency measurement techniques exploiting a perturbed cavity resonator have recently gained significant attention.…”