# The Biocompatibility of Wireless Power Charging System on Human Neural Cells
## 2 Material and Methods
### Simulation Analysis of the EMF Intensity and Distribution within Proposed WPT System  
The need for the identification of the magnitudes of magnetic field is required before experiments with EM exposure will be realized. There are several ways to identify EMF intensities, while the first one can be done experimentally and the second through the use of a verified simulation model. As the laboratory instrumentation for experimental measurement of EMF radiation could be complex and expensive, we utilized the second possibility, i.e., highly accurate simulation model of proposed WPT system [24].  
The equivalent circuit used for the identification of the EMF intensities is shown in Figure 5. The model considers the electrical and magnetic domain, while the electrical circuit settings are given in Table 1. Figure 6 represents arrangement and location of the measuring points within the set-up.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Circuit Element** & **Value** & **Point (+)** & **Point (-)** \\ \hline
**Ground** & GND & 0 & 0 \\
**Voltage source** & VMAX*sin(\(\omega\)t) & 0 & 1 \\
**Capacitor 1** & 1/(\(\omega\)2*comp1.mf.LCoil\_1) [F] & 1 & 2 \\
**Resistor 1** & RCoil [G] & 2 & 3 \\
**External 1 vs. V1** & Coil voltage (mf3/coil1) & 3 & 0 \\
**External 1 vs. V2** & Coil voltage (mf3/coil2) & 0 & 6 \\
**Resistor 2** & RCoil2 [G] & 6 & 7 \\
**Capacitor 2** & 1/(\(\omega\)2*comp2.mf2.LCoil\_1) [F] & 7 & 8 \\
**Load** & RLOAD [G] & 8 & 0 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Settings of the electronic circuit simulation model.  
Figure 4: System of coupling coils with adjustable transfer distance (**left**) and reconfigurable magnetic shielding (**right**).  
Figure 5: Electrical circuit definition within the electrical domain of the FEM simulation model.  
Magnetic flux was identified within the area, where neural cells (sample) were located, while three cutting lines per sample were evaluated. It was defined that samples were located within the area between the transmitter and receiver (28 mm from transmitter), and within the area above the receiver (28 mm from the secondary coil).  
To identify magnetic field intensities, which are required for the exposure of neural cells, the parametric simulation analyses were performed to identify the target value of magnetic induction. The example of the simulation result is shown in Figure 7. As can be seen in Figure 7, approximately 1.2 mT was achieved on the bottom exposure sample, and approximately 0.3 mT was exposed on the top sample, while Input/Output parameters of WPT system for experiments are identified as follows: Input DC voltage 249.5 V; Resistive load 48.9 \(\Omega\); Main Resonant Frequency 85 kHz--switching frequency of high-frequency inverter; Higher Resonant Frequency 87 kHz.  
Figure 6: The scheme of the biological samples location in the WPT system during exposure.  
Figure 7: Simulation results of the distribution of magnetic induction within a system of coils (operating frequency, 87 kHz; transmitting power, 1450 W).  
Investigating the frequency characteristic for the above parameters, Figure 8 represents dependency of the transmitted power on the switching frequency of the inverter. The value of power transfer for the investigated EMF exposure is approximately 1.5 kW.  
It must be noted that the above parameters of the WPT system represent scaled exposure because of the use of neural human cells. If different exposure samples are considered, i.e., human tissues, or larger biological structures, the EMF intensities should be higher and can be modified in the way of variation of Input/Output parameters of the WPT system.