Millimeter-Wave Heating in In Vitro Studies: Effect of Convection in Continuous and Pulse-Modulated Regimes

Rosa Orlacchio (1, 2) , Maxim Zhadobov (1) , Stanislav I. Alekseev (3) , Denys Nikolayev (4) , Ronan Sauleau (1) , Yann Le Page (5) , Yves Le Drean (5)

1 IETR - Institut d'Électronique et des Technologies du numéRique
2 XLIM - XLIM
3 RAS - Russian Academy of Sciences [Moscow]
4 EPFL - Ecole Polytechnique Fédérale de Lausanne
5 Irset - Institut de recherche en santé, environnement et travail

Shallow penetration of millimeter waves (MMW) and non-uniform illumination in in vitro experiments result in a non-uniform distribution of the specific absorption rate (SAR). These SAR gradients trigger convective currents in liquids affecting transient and steady-state temperature distributions. We analyzed the effect of convection on temperature dynamics during MMW exposure in continuous-wave (CW) and pulsed-wave (PW) amplitude-modulated regimes using micro-thermocouples. Temperature rise kinetics are characterized by the occurrence of a temperature peak that shifts to shorter times as the SAR of the MMW exposure increases and precedes initiation of convection in bulk. Furthermore, we demonstrate that the liquid volume impacts convection. Increasing the volume results in earlier triggering of convection and in a greater cooling rate after the end of the exposure. In PW regimes, convection strongly depends on the pulse duration that affects the heat pulse amplitude and cooling rate. The latter results in a change of the average temperature in PW regime. (c) 2019 Bioelectromagnetics Society.

Keywords: in vitro experiments; local heating; thermal dosimetry; millimeter waves; Grashof number

Domains: Engineering Sciences [physics]

Rosa Orlacchio, Maxim Zhadobov, Stanislav I. Alekseev, Denys Nikolayev, Ronan Sauleau, et al.. Millimeter-Wave Heating in In Vitro Studies: Effect of Convection in Continuous and Pulse-Modulated Regimes. Bioelectromagnetics, 2019, 40 (8), pp.553-568. ⟨10.1002/bem.22223⟩. ⟨hal-02355635⟩