Conductivity and frequency dependent specific absorption rate

Recently, a number of contradicting results have been reported regarding the electromagnetic (EM) energy absorption by highly conductive materials in a liquid phase. The argument rises from the fact that higher conductive media absorb more electromagnetic energy; this however would be constrained by the localized field values that are dictated by the dielectric variations, which may reduce the absorption rate. Using salted water as an example, a systematic investigation of the mechanisms of EM absorption in the presence of highly conductive materials is conducted in this work. A theoretical model is developed, which is supported by both numerical and experimental studies. The influence of salt concentration, dielectric properties, boundary conditions, and EM frequency on the specific absorption rate (SAR) is carefully examined. The results show that the presence of salt in water modifies the dielectric properties significantly in the RF range, while the effect is less prominent in the microwave range. The SAR is highly dependent on the conductivity and frequency, as well as the employed instrument that dictates the surrounding boundary conditions. To suit different applications, the SAR can be optimized by proper consideration of the concentration of high conductivity material, operating frequency, and instruments.