Biochemical liquids permittivity characterization technique based on whispering-gallery mode resonator with microfluidic channel

We present the accurate microwave characterization technique for measuring the complex permittivity of biochemical liquids of sub-microliter/nanoliter volumes. The technique is developed on the basis of high-quality whispering-gallery mode sapphire resonator with microfluidic channel filled with liquid under test. Experimental data are obtained in Ka-band for the aqueous solution of cytochrome C, which can be used in the field of biosensors. To find the complex permittivity of the solution the special calibration procedure with application of COMSOL Multiphysics commercial software was performed.