(6bc) Microwave Assisted Heating of Human Blood at 2450 MHz Frequency Using Various Composite Supports

Abstract — The growing interest in the use of microwaves to process materials is primarily due to ‘volumetric heating’. Microwave energy has been beneficial for a spectrum of applications in engineering and medical fields especially for heating, thawing, drying, warming and material processing. Warming/heating of blood sample is a very common medical practice and microwave heating could be potentially very useful due to the advantages such as rapid, controlled, selective and uniform heating effects. In Blood Bank, blood samples (whole blood) are usually preserved at low temperatures (1 to 6 °C) with permitted storage periods of 2-4 weeks and for longer storage periods (more than months) blood samples need to be preserved at very low temperatures (-30 to -65 °C). Warming/heating of blood sample collected from blood bank is a very essential medical practice before blood transfusion. Conventional method of blood sample heating/warming may not be useful for emergency situations as it takes hours to heat the blood sample. However, microwave heating could be extremely useful for blood sample warming/heating especially during emergency situations as it takes very short time (few minutes only). The present work has been carried out to study efficient heating due to microwaves for one-dimensional (1-D) human blood samples placed on Teflon, various ceramic (Al₂O₃, SiC), and composite supports. Maxwell’s equation for electromagnetic wave propagation (electric field equation) and the non-linear heat conduction equation (energy balance equation) with the appropriate boundary conditions are simultaneously solved using Galerkin’s finite element method to obtain power absorption and transient temperature profile for the blood sample-support assembly. A preliminary study has been carried out via average power vs sample thickness diagram to estimate microwave power absorption within blood samples for various cases. In addition, support thickness sensitivity analysis has also been carried out and suitable support thickness has been recommended. The maxima in average power, also termed as ‘resonances’, are observed for specific blood sample thicknesses and the two consecutive resonances of significant magnitudes are termed as R₁ and R₂ modes. For all cases, it is observed that microwave power absorption is enhanced in presence of metallic and composite supports during both R₁ and R₂ modes. The efficient heating strategies characterized by ‘large heating rates’ with ‘minimal thermal runaway’ i.e. uniform temperature distributions within the sample have been assessed for both small and large blood sample thicknesses. Based on the detailed spatial distributions of power and temperature for various cases, suitable combinations of supports have been recommended as optimal heating strategies for blood samples corresponding to both R₁ mode and R₂ mode. Present study recommends the efficient way to use microwaves in a single mode waveguide and the heating scheme can be suitably extended for heating of any other animal blood samples with known/ measurable dielectric properties.