Due to the expected mass deployment of millimeter‐wave wireless technologies, thresholds of potential millimeter‐wave‐induced biological and health effects should be carefully assessed. The main purpose of this study is to propose, optimize, and characterize a near‐field exposure configuration allowing illumination of cells in vitro at 60 GHz with power densities up to several tens of mW/cm2. Positioning of a tissue culture plate containing cells has been optimized in the near‐field of a standard horn antenna operating at 60 GHz. The optimal position corresponds to the maximal mean‐to‐peak specific absorption rate (SAR) ratio over the cell monolayer, allowing the achievement of power densities up to 50 mW/cm2 at least. Three complementary parameters have been determined and analyzed for the exposed cells, namely the power density, SAR, and temperature dynamics. The incident power density and SAR have been computed using the finite‐difference time‐domain (FDTD) method. The temperature dynamics at different locations inside the culture medium are measured and analyzed for various power densities. Local SAR, determined based on the initial rate of temperature rise, is in a good agreement with the computed SAR (maximal difference of 5%). For the optimized exposure setup configuration, 73% of cells are located within the ±3 dB region with respect to the average SAR. It is shown that under the considered exposure conditions, the maximal power density, local SAR, and temperature increments equal 57 mW/cm2, 1.4 kW/kg, and 6 °C, respectively, for the radiated power of 425 mW. Bioelectromagnetics 33:55–64, 2012. © 2011 Wiley Periodicals, Inc.

A near-field millimeter-wave exposure system configuration allowing cell culture exposures at 60 GHz is proposed and characterized. The design was optimized to obtain relatively homogeneous distribution of the specific absorption rate (SAR) within the cell layer for the incident power densities ranging from 0 up to 67 mW/cm2 for the input power of 500 mW. Averaged over the cell monolayer volume SAR is computed and the results are provided as a function of the input power. This exposure system will be used in in vitro experiments to determine power thresholds corresponding to the functional modifications in the human cell.

The main purpose of this article is to study potential biological effects of low-power millimeter waves (MMWs) on endoplasmic reticulum (ER), an organelle sensitive to a wide variety of environmental insults and involved in a number of pathologies. We considered exposure frequencies around 60 GHz in the context of their near-future applications in wireless communication systems. Radiations within this frequency range are strongly absorbed by oxygen molecules, and biological species have never been exposed to such radiations in natural environmental conditions. A set of five discrete frequencies has been selected; three of them coincide with oxygen spectral lines (59.16, 60.43, and 61.15 GHz) and two frequencies correspond to the spectral line overlap regions (59.87 and 60.83 GHz). Moreover, we used a microwave spectroscopy approach to select eight frequencies corresponding to the spectral lines of various molecular groups within 59-61 GHz frequency range. The human glial cell line, U-251 MG, was exposed or sham-exposed for 24 h with a peak incident power density of 0.14 mW/cm(2). The average specific absorption rate (SAR) within the cell monolayer ranges from 2.64 +/- 0.08 to 3.3 +/- 0.1 W/kg depending on the location of the exposed well. We analyzed by quantitative reverse transcription-polymerase chain reaction (RT-PCR) the level of expression of two endogenous ER-stress biomarkers, namely, the chaperones BiP/GRP78 and ORP150/GRP170. It was found that exposure to low-power MMW does not significantly modify the mRNA levels of these stress-sensitive genes suggesting that ER homeostasis is not altered by low-power MMW at the considered frequencies.

We investigate potential biological effects of low-power millimeter-wave radiation on human cell viability and intracellular protein homeostasis. A specific exposure system allowing to perform far-field exposures with power densities close to those expected from the future wireless communications in the 60-GHz band has been developed and characterized. Specific absorption rate (SAR) values were determined for the biosamples under test using the FDTD method. It was shown that millimeter-wave radiation at 60.42 GHz and with a maximum incident power density of 1 mW/cm(2) does not alter cell viability, gene expression, and protein conformation.

Millimeter waves (MMW) at frequencies around 60 GHz will be used in the very near future in the emerging local wireless communication systems and the potential health hazards of artificially induced environmental exposures represent a major public concern. The main aim of this study was to investigate the potential effects of low-power MMW radiations on cellular physiology. To this end, the human glial cell line, U-251 MG, was exposed to 60.4 GHz radiation at a power density of 0.14 mW/cm(2) and potential effect of MMW radiations on endoplasmic reticulum (ER) stress was investigated. ER is very sensitive to environmental insults and its homeostasis is altered in various pathologies. Through several assay systems, we found that exposure to 60.4 GHz does not modify ER protein folding and secretion, nor induces XBP1 or ATF6 transcription factors maturation. Moreover, expression of ER-stress sensor, BiP/GRP78 was examined by real-time PCR, in exposed or non-exposed cells to MMW radiations. Our data demonstrated the absence of significant changes in mRNA levels for BiP/GRP78. Our results showed that ER homeostasis does not undergo any modification at molecular level after exposure to low-power MMW radiation at 60.4 GHz. This report is the first study of ER-stress induction by MMW radiations.

A computer-aided design tool for the optimization of three-dimensional integrated lens antennas (ILAs) is described. The optimization procedure is based on a genetic algorithm (GA) coupled to the hybrid geometrical/physical optics (GO/PO) method of analysis. It is the first time that this global numerical search technique has been applied to design 3-D shaped ILAs. To validate the proposed methodology and the numerical algorithms, two single-material ILAs are optimized and fabricated at 28 GHz. They radiate a sectoral beam and an elliptical Gaussian beam, respectively. The lens prototypes are fed by an aperture-coupled microstrip patch antenna. The influence of the lens dimensions and internal reflections on the far-field radiation patterns is also highlighted when designing shaped lenses. Comparison between experiments and numerical predictions (GO/PO and finite-difference time-domain) successfully validates our design tool.

Due to the increasing interest in millimeter-wave (MMW) applications for wireless communication systems, the investigation of their potential biological effects is of utmost importance. In this paper, we report experimental results of the study of interactions between low-power radiation at 60 GHz and artificial models of biological membranes. In the first part of this study, we demonstrate an increase of superficial pressure of phospholipid monolayers during MMW exposure. Two of the most prominent in quantity lipid constituents of biological membranes, dipalmitoylphosphatidylcholine and dioleoylphosphatidylcholine, are considered. The role of different radiation parameters, namely, power density, polarization, amplitude modulation, permanent, and discontinuous exposure, is discussed. The results have proved to be reproducible in independent experiments. In the second part of this study, through atomic force microscopy analysis, we investigate the influence of MMW radiation on the microdomain distribution in mixed phospholipid monolayers with phase separation. No significant modifications are observed in microdomain distribution after 5 h of exposure. The main outcomes of this study lead to the conclusion that short-term low-power MMW exposures result in an increase of lateral pressure of the phospholipid monolayer, but their influence is not sufficiently strong to disturb phospholipid microdomain organization in biomembranes.

The rapid development of wireless communication systems with the operating frequency around 60GHz states the question about the environmental safety and health risk of artificially induced exposures. To investigate the basic mechanisms of the potential bioelectromagnetic interactions we studied biophysical properties of artificial biological membranes exposed to low-power millimeter-wave (MMW) radiations at 60 GHz. Different radiation parameters of the exposure were investigated. Electromagnetic field and power-density distributions were calculated analytically and confirmed by measurements. Experimental results showed variations in the superficial pressure dynamics of the membranes even for very low power density values. Topographic analysis of the membranes surface by the atomic force microscopy (AFM) did not reveal any effect of the MMW radiations on the phoshpolipid domain organization in the mixed phospholipid membranes.

The purpose of this study was to determine whether millimeter waves exposure at 60GHz, upcoming to use for indoor high rate communications in local area networks, could lead to a stress response in human brain cells. U-251 MG cell line was sham-exposed or exposed to low power density millimeter radiation for different duration, from 1h to 33h. Using the transfection technique, we analyzed the gene expression for reporter genes previously shown highly sensitive to many environmental insults. We have tested the influence of 60GHz radiations on 3 different gene expression systems, overlaying the main cellular response pathways to physical and chemical stresses. No statistically significant difference was detected in transcriptional activity of reporter genes after radiation exposure. These results suggest that radiation in the frequency range around 60GHz is not a stressor strong enough to modify the stress-sensitive gene expression.