Open-Ended Waveguide Measurement and Numerical Simulation of the Reflectivity of Petri Dish Supported Skin Cell Monolayers in the mm-wave Range

Abstract

Open-ended waveguide reflectometry is a promising tool for permittivity and other material properties calculation at mm-waves (30-300 GHz). Measurement of the reflection coefficient does not require sample manipulation, allowing in vivo and in vitro non destructive studies on cells. Here we used this technique for measuring the power reflection coefficient (reflectivity) of water and Petri dish supported human skin melanoma and keratinocyte cell cultures, in the 53-72 GHz frequency range. The dependence of the reflectivity on polystyrene or glass thickness of the Petri base plate and on the cell layer thickness was analyzed. Permittivity data were then easily retrieved by using a plane wave-dominant mode approach for formulating the reflectivity at the aperture of the flange-mounted open-ended rectangular waveguide probe. Limits and validity of such an approximate approach were analyzed and compared with full-wave near field formulations for which magnitude and phase of the reflection coefficient must be measured and solved using complicated systems of integral equations and extensive numerical calculation. Finally, Petri dish reflectivity measured by the open-ended waveguide method was compared with that numerically simulated under far-field exposure conditions used in a large number of in vitro studies. Such an analysis showed that, under certain conditions, open-ended reflectivity values approach the far field ones.

The influence of millimeter waves on the physical properties of large and giant unilamellar vesicles

“…This result is consistent with the very low power densities incident on the sample (Table 1) and the fact that, in the downward exposure setup used, about half of the IPD is reflected back [9] and the fraction transmitted into the sample exponentially decays as a function of the propagation direction with a rate that depends on its depth of penetration in the aqueous medium (δ). Assuming that δ ranges from about 0.35 mm up to about 0.40 mm in the frequency range studied [9], it can be calculated that 90% of the power density is absorbed within the first 0.4 mm of the suspension. However, as the presence of the sensor in the liquid could perturb the MMW field distribution [40], a remote temperature recording is desirable in order to obtain correct surface-temperature dynamics data on the convection process during MMW irradiation [41].…”

“…In this frequency range, there are significant parts of the rotational modes of water molecules [8][9][10][11][12], fluctuations of atoms in organic molecules and hydrogen bonds. Biologically relevant processes can therefore be initiated using radiation in this frequency domain [13].…”

Effect of millimetre waves on phosphatidylcholine membrane models: a non-thermal mechanism of interaction

“…4,5,12 It is worth noting that, even if this would occur, spectral resonances can be hardly tuned due to the water-dominated absorbance of the MMW energy in biological media. 18,19 In recent years, membrane modelling and simulations have been increasingly used in order to study wave interaction with membranes, including the effects of MMWs at a molecular level. [20][21][22][23][24][25][26][27][28][29] Exposure at 60 GHz and low power densities (mW cm À2 ), signicantly affect the lateral pressure of the phospholipid monolayer.…”