Enhanced fluid characterization in the millimeter-wave band using Gap Waveguide Technology

Abstract

Microfluidic systems have emerged as a promising technology for molecular analysis, biodefence and microelectronics. Fluid sensing by microwave sensors based on the RF analysis offers new possibilities for the characterization of mediums by non-invasive methods. Several techniques are available in the frequency domain for analyzing the dielectric properties of liquids and their composition. Among them, one of the most accurate techniques is the resonant cavity methods. However, these techniques are incompatible with lab-on-chip process due its dimensions in the millimeter-wave band. In this context, a new structure called gap waveguide appears as a good candidate to overcome the principal drawbacks of the classical resonant cavities. This thesis presents the development of the gap waveguide technology in the millimeter-wave band. Other conventional technologies are discussed as well, to compare them with the performance in terms of gap waveguide losses. We also present the resonator design based on gap waveguide capable of working in the microfluidic sensing domain in the millimeter-wave band. In this context, we propose a comparative study between gap waveguide and Substrate Integrated Cavity (SIC) with the aim to characterize the fluid permittivity at 60 GHz. With this purpose, several prototypes have been manufactured with Printed Circuit Board (PCB) and Low Temperature Co-fired Ceramic (LTCC) technologies. An important experimental was carried out to validate work some critical steps in the LTCC process which are important for the gap waveguide manufacturing, particularly those related with the creation of cavities using LTCC materials.