Microwave Sensors for the Dielectric Characterization of Biological Cells
Final Report Abstract
The project aimed for single cell characterization. For this purpose, microfluidic sensors were developed in microtechnology, as widely done in this field. They were designed with a novel mechanical trap and various electrode arrangements. Two of these arrangements are planar sensors and a third one utilizes a parallel plate capacitor with a guard electrode. The latter is a known method to mitigate the effect of fringing fields at lower frequencies. The developed implementation at high frequencies is a novelty. To enable the extraction of the broadband complex permittivity, a calibration method was developed for electrically small samples. Due to a change in the commercial manufacturing process and the resulting increased cost, only one production run could be realized instead of two, as originally planned. To compensate for the missing optimization run, the sensors were designed in several geometrical variants. This and the global pandemic resulted in several changes to the initial schedule. The delivered sensors were used to measure two different cell lines. Each cell line was measured with living and two versions of dead cells. In all cases, the dielectric contrast to the surrounding culture medium proved to be large enough to be detectable. The measurement results also revealed a significant and measurable difference between the living cells of the two versions, namely CHO and HepG2 cell. Additionally, dead cells could be distinguished from living cells. There are even indications that the way of induced cell death, namely with either formalin or ethanol, could be distinguished with the permittivity footprint. Although the planned time schedule and the planned work were slightly changed, the project goals were reached. The developed and employed calibration procedure is a significant contribution towards permittivity extraction of small samples. The designed and manufactured sensors successfully measured the broadband complex permittivity of single cells in various versions. The discovered contrasts between different cell lines and pathological states open doors for new sensor ideas and can provide justification for clinical studies in the future. One highlight of the project was the successful high-school project. It started a novel university-school cooperation during which four pupils developed a temperature sensing solution for microchips. The pupils gathered their first insights into university research projects and report great experience.
Publications
- “A Capacitive Microwave Sensor with Guard Electrodes for Biological Cell Characterization”, IEEE MTT-S International Microwave Biomedical Conference (IMBioC 2020)
A. Savić, A.F. Jacob
(See online at https://doi.org/10.1109/IMBIoC47321.2020.9385030) - “A Capacitive Microwave Sensor with Guard Electrode for Single Cell Characterization”, IEEE Journal of Electromagnetics, RF and Microwaves in Medicine and Biology
A. Savić, F. Freiberger, R. Pörtner, A.F. Jacob
(See online at https://doi.org/10.1109/JERM.2021.3078850)
