This paper compares two types of microfluidic sensors that are designed for operation in ISM (Industrial, Scientific, Medical) bands at microwave frequencies of 2.45 GHz and 5.8 GHz. In the case of the first sensor, the principle of operation is based on the resonance phenomenon in a microwave circuit filled with a test sample. The second sensor is based on the interferometric principle and makes use of the superposition of two coherent microwave signals, where only one goes through a test sample. Both sensors are monolithic structures fabricated using low temperature co-fired ceramics (LTCCs). The LTCC-based microwave-microfluidic sensor properties are examined and compared by measuring their responses for various concentrations of two types of test fluids: one is a mixture of water/ethanol, and the other is dopamine dissolved in a buffer solution. The experiments show a linear response for the LTCC-based microwave-microfluidic sensors as a function of the concentration of the components in both test fluids.

Microwave treatment can reduce the time of selected syntheses, for instance of gold nanoparticles (AuNPs), from several hours to a few minutes. We propose a microfluidic structure for enhancing the rate of chemical reactions using microwave energy. This reactor is designed to control microwave energy with much higher accuracy than in standard devices. Thanks to this, the influence of microwave irradiation on the rate of chemical reactions can be investigated. The reactor consists of a transmission line surrounded by ground metallization. In order to deliver microwave energy to the fluid under test efficiently, matching networks are used and optimized by means of numerical methods. The monolithic device is fabricated in the low temperature co-fired ceramics (LTCC) technology. This material exhibits excellent microwave performance and is resistant to many chemical substances as well as high temperatures. Fabrication of the devices is described in detail. Measurements of microwave parameters are performed and differences between simulation and experiment results are discussed. Finally, the usefulness of the proposed device is proved in exemplary synthesis.

Microwave treatment can reduce the time of selected syntheses, for instance of the gold nanoparticles, from several hours to the few minutes. We propose microfluidic structure for enhancing rate of chemical reactions using microwave power. This reactor is designed to control microwave power with much higher accuracy than in standard devices. Thanks to this the influence of microwave irradiation on the rate of chemical reactions can be investigated. The reactor consists of transmission line surrounded by the ground metallization. In order to efficient deliver microwave power to the fluid matching networks are optimized using numerical methods. The monolithic device is fabricated in the Low Temperature Co-fired Ceramics (LTCC) technology. This material exhibits excellent microwave performance, and is resistant to many chemical substances as well as high temperature. Fabrication of the devices is described in details. Measurements of microwave parameters are performed and differences between simulation and experiment results are discussed.

Purpose: – The purpose of this paper was to investigate the influence of non-uniform temperature distribution inside a box furnace during the firing process on electrical properties of the low-temperature co-fired ceramic (LTCC) materials used in radio frequency (RF)/microwave applications. Design/methodology/approach: – The authors studied the change in dielectric constant of two popular LTCC materials (DP 951 and DP 9K7) depending on the position of their samples inside the box furnace. Before firing of the samples, temperature distribution inside the box furnace was determined. The dielectric constant was measured using the method of two microstrip lines. Findings: – The findings showed that non-uniform temperature distribution with spatial difference of 6°C can result in 3-4 per cent change of the dielectric constant. It was also found that dielectric constant of the two tested materials shows disparate behavior under the same temperature distribution inside the box furnace. Practical implications: – The dielectric constant of the substrate materials is crucial for RF/microwave applications. Therefore, it was shown that 3-4 per cent deviation in dielectric constant can result in considerable detuning of microwave circuits and antennas. Originality/value: – To the best of the authors’ knowledge, the quantitative description of the impact of temperature distribution inside a box furnace on electrical properties of the LTCC materials has never been published in the open literature. The findings should be helpful when optimizing production process for high yield of reliable LTCC components like filters, baluns and chip antennas.

The integral equation -method of moments approach to analyzing a cavity backed, slot excited dielectric resonator antenna is validated experimentally (by measurements). First, the closed rectangular metal box is considered to validate the cavity treatment. Then, the whole DRA structure, i.e. the cavity along with the slot and dielectric resonator, is tested to prove definitively correctness of the approach used.