Optimized Sensor for Broadband Dielectrometry of Biological Liquids of Small Volume

In this article, the results of a tailored calibration scheme applied to a transmission line sensor for measuring the relative permittivity of biological liquids in a broad microwave frequency range are discussed. The microwave sensor design enables measurements of relative permittivity values of biological samples with a small volume of only 70nl. The relative permittiv-ity is extracted for aqueous solutions of Sodium Chloride (NaCl) and Bovine Serum Albumin (BSA) over a broadband range from 10 MHz to 40 GHz at a constant temperature of 21.5 ±0.4° C. The measured permittivity of NaCI solution matches closely with simulated and literature data with relative error of
$\Delta\varepsilon_{r}=0.51\%$
at 20 GHz. Further, the broadband relative permittivity results are compared to extracted permittivity values obtained from a resonant measurement method based on a quartz whispering gallery mode resonator at discrete frequencies between 30 GHz and 40 GHz.