Electrical characterization of biological solutions for implantable antenna design

Miniaturization techniques enables the use of antennas in sensing systems at cellular and molecular level due to its reduced size. In this kind of systems, the implanted sensors are usually surrounded by a lossy biological medium which affects antenna behaviour. For reaching the best performance of the implanted antenna, the effect of the medium needs to be electrically characterized and considered during the design process. This paper presents the electrical characterization of some biological solutions which are generally used in sensing systems at cellular and molecular level: Phosphate-Buffered Saline (PBS), Dulbecco's Modified Eagle Medium (DMEM) and Dulbecco's Modified Eagle Medium with 10% Fetal Bovine Serum (DMEM + 10% FBS). Measurement results of these water-based mediums from 0.2 to 20 GHz using an open-air coaxial probe are performed and presented in this work. Moreover, the complex permittivity variation with temperature is measured and compared with the values of water. Finally, the parameters of the two-pole Cole-Cole model are extracted for each biological medium and for every temperature combination. The calculated Cole-Cole theoretical curves can be used in the antenna design process.