Broadband microfluidic dielectrometry of biochemical liquids based on microwave precision measurement technique

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The precise measurement of the complex permittivity of highly lossy materials, especially in the microwave range, is of central importance for the monitoring of biological fluids. Despite a multitude of measurement techniques available, there is a lack of reliable approaches for microwave characterization of biological fluids in small volumes. Therefore, it is extremely important to develop novel methods that allow i) direct measurements of the electromagnetic properties of the liquids, ii) to develop a method to characterize liquids in smallest volumes from 1 µL to 1 nL at temperatures below 0°C, and iii) to characterize liquids with a high loss tangents. The solution of this problem is of high scientific and application-oriented importance. Nevertheless, the crucial challenges to the accuracy and sensitivity of such measurements of lossy fluids have not been solved yet. Therefore, direct measurements of complex permittivity is of special significance. Today, the non-resonant methods based on coaxial lines or metal waveguides are widely used. However, they have low sensitivity and require large amounts of fluid compared to the very small volumes that is required for resonant methods.This project aims to develop scientific principles of microwave dielectrometry on biological fluids that allow sensitive, direct measurements of the complex permittivity of small volume lossy fluids at temperatures below 0°C. The focus here is on a technique that enables highly accurate measurements. Our previous studies show that the problems can be solved using specially designed whispering gallery mode (WGM) dielectric resonators and microfluidics/nanofluidics. In addition, a broadband method based on microfluidics will be developed as a reference method, which is characterized by optimized sensitivity while minimizing the measurement volume. Here the main tasks are explained: i) study of the theoretical basis for the design and fabrication of new types of measurement cells for microwave studies of lossy liquids of small volumes, ii) solving the inverse-electromagnetic problem in determining the complex permittivity from the measurement results. Here, a dielectrometer prototype with new measuring cells will be developed and test measurements will be performed on the most important biological fluids (albumin, glucose, cytochromes C, aqueous solutions of DNA, etc.).The successful completion of this project opens perspectives for a new type of dielectrometry in biology and medicine.