## 4 Discussion  
In this work, a novel electroporator has been presented, which is based on H-bridge circuit topology and the double-crowbar driving technique. Such an approach enabled the operation of the SiC MOSFETs beyond their datasheet ratings with close to minimal rise and fall times. The summary of the parameters is presented in Table 1.  
It should be noted that we have used the latest solutions available, which were provided either by our or other groups, and combined them in one generator. The proposed driving technique allowed us to extend the range of parametrical flexibility. Additionally, the three-stage driving circuit can support a lot more MOSFET drivers, thus the number of MOSFETs in each wing can be at least doubled if higher voltages are required. The number of microcontroller pins will still be four to drive them all. However, it is important to account for the thermal effects in the pn junction of MOSFETs involved in the crowbar wings of the H-bridge topology. In the presented prototype, the current can reach up to 300 A, thus if a higher voltage is used, it is likely that a more powerful MOSFET should be used (e.g., Cree, C2M0045170D). Another advantage of the proposed driving method is the zero relaxation times between opposite phase pulses. This can play a significant role in studying the cancellation effects happening during ultrashort pulses [30]. The limitations of the generator can also be highlighted. Firstly, we limited the generator to 3 kV and 40 A, sufficient for all reversible electroporation applications. However, if irreversible nanosecond electroporation is required, we believe that the number of MOSFETs in a stage should be doubled, which will increase both the voltage and current handling. In such a scenario, we would aim for a 6 kV/80 A device using the same circuit and driving topology we proposed in this paper since it offers good scalability. Additionally, our device is limited by the minimum duration step of 33 ns, which is due to the 32 MHz microcontroller. If better precision is required, either a computer-controlled or/and FPGA interface should be introduced, or/and solutions using auxiliary four-channel low power generators can be implemented too. Nevertheless, the dynamic characteristics of the generator will still be limited by the SiC MOSFET technology as in all other available devices in the literature. The potential applications and parametrical flexibility of the proposed electroporator can be highlighted as the main factors affecting the novelty and actuality. The short nanosecond pulses enable better control of the energy of the burst due to a significantly higher number of pulses in a sequence and shorter rise and fall times. Compared to the standard microsecond procedures, nanosecond sequences also involve several-fold higher PEF amplitudes, which is beneficial in terms of a more uniform tumor exposure [31]. Additionally, the capabilities to trigger additional cellular mechanisms in the nanosecond pulse range are frequently reported in the literature [32; 33; 34]. At the same time, bipolar pulses result in a higher frequency component compared to the unipolar ones, thus the heterogeneity of tumors can be better compensated [35]. Asymmetrical nanosecond pulses can be potentially exploited in the cancellation phenomena [30], providing a base for new and selective electrochemotherapy protocols. Lastly, we speculate that the high frequency nanosecond protocols, which can be derived using the proposed machine, can help to \begin{table}
\begin{tabular}{c c} \hline
**Parameter** & **Value** \\ \hline Voltage & Up to 3 kV \\ Current & Up to 40 A \\ Pulse duration & 65 ns–100 μs \\ Duration step & 33 ns \\ Repetition frequency & Up to 5.4 MHz \\ Pulse shape & Unipolar; bipolar; arbitrary \\ \hline \end{tabular}
\end{table} 
Table 1: The parameters of the developed electroporator. significantly reduce the muscle contractions during the treatment, similar to the H-FIRE procedure [20; 36].