Studying the response of neuronal networks to radiofrequency signals requires the use of a specific device capable of accessing and simultaneously recording neuronal activity during electromagnetic fields (EMF) exposure. In this study, a Microelectrode Array (MEA) that records the spontaneous activity of neurons is coupled to an open transverse electromagnetic (TEM) cell which propagates EMF. We characterize this system both numerically and experimentally at 1.8 GHz. Two MEA versions were compared, for the first time, to determine the impact of their design dissimilarities on the response to EMF. Macroscopic and microscopic measurements using respectively a fiber-optic probe and a temperature-dependent fluorescent dye (Rhodamine-B) were carried out. Results indicate that one MEA shows more stability toward the changes of the surrounding environment compared to the other MEA. Using a fiber-optic thermometer, the measured specific absorption rate (SAR) probe value in the center of the more stable MEA was 5.5±2.3 W/kg. Using a Rhod-B microdosimetry technique, the measured SAR value at the level of the MEA electrodes was 7.0±1.04 W/kg. SAR values are normalized per 1-W incident power. Due to the additional metallic planes and a smaller chip aperture, this new recording chip is steadier in terms of SAR and temperature stability allowing high exposure homogeneity as required during biological experiments. A typical neuronal activity recording under EMF exposure is reported.

Exposing living cells to a certain level of electromagnetic field (EMF) might induce some biological effects including temperature elevation. In this article, we studied two exposure systems at the macro and microscopic levels, allowing the study of the EMF effect on the biological samples exposed to 1.8-GHz signals. The macrosystem was an open transverse electromagnetic (TEM) cell that served as a dosimetry reference for defining limitations and optimal conditions for the temperature calibration using Rhodamine B (RhodB). The microfluidic microsystem was based on the coplanar waveguide (CPW) electrodes. Temperature measurements are carried out with a fluorooptic probe to extract specific absorption rate (SAR) values that are compared with numerical dosimetry, based on an FDTD method. After calibration, the fluorescence fits well with the temperature variation measured by the probe. To investigate dosimetry at a microscopic level, the fluorescence of the temperature-dependent dye RhodB was measured by fluorescence microscopy within the microfluidic channel or the biological cells. Results evidenced that the technique is applicable for RhodB concentrations higher than 1 µm with a value of 50 µm recommended for reliable experiments. For steady detection and SAR assessments, temperature variations of a few tenths of degrees were required.

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Exposing living cells to a certain level of Electromagnetic Field (EMF) might induce some biological effects including temperature elevation. In this paper, we show the dosimetry of exposure systems such as an Open Transverse Electro-Magnetic (TEM) cell allowing the study of the effect of EMF on biological samples exposed to 1.8 GHz signals.Temperature measurements are carried out with a fluorooptic probe to extract specific absorption rate (SAR) values that are compared to numerical dosimetry, based on a FDTD method. To investigate dosimetry at a microscopic level the fluorescence of the temperature dependent dye Rhodamine B was measured with fluorescence microscopy. The results are confirmed by measurements and simulations with a SAR of 13.9 and 11.8 W/kg for 1 W incident power, respectively. Results evidence that the objective working distance of the microscope strongly influence SAR values. After calibration, the fluorescence fits well with the temperature variation measured by the probe.