Validation of a SPICE Model for High Frequency Electroporation Systems

In this paper, we present an analysis and a validation of a simulation program with integrated circuit emphasis (SPICE) model for a pulse forming circuit of a high frequency electroporation system, which can deliver square-wave sub-microsecond (100–900 ns) electric field pulses. The developed SPICE model is suggested for use in evaluation of transient processes that occur due to high frequency operations in prototype systems. A controlled crowbar circuit was implemented to support a variety of biological loads and to ensure a constant electric pulse rise and fall time during electroporation to be independent of the applied buffer bioimpedance. The SPICE model was validated via a comparison of the simulation and experimental results obtained from the already existing prototype system. The SPICE model results were in good agreement with the experimental results, and the model complexity was found to be sufficient for analysis of transient processes. As result, the proposed SPICE model can be useful for evaluation and compensation of transient processes in sub-microsecond pulsed power set-ups during the development of new prototypes.This article belongs to the Section Circuit and Signal Processin

Magnetoresistance and Magnetic Relaxation of La-Sr-Mn-O Films Grown on Si/SiO₂ Substrate by Pulsed Injection MOCVD

The results of magnetoresistance (MR) and resistance relaxation of nanostructured La1−xSrxMnyO3 (LSMO) films with different film thicknesses (60–480 nm) grown on Si/SiO2 substrate by the pulsed-injection MOCVD technique are presented and compared with the reference manganite LSMO/Al2O3 films of the same thickness. The MR was investigated in permanent (up to 0.7 T) and pulsed (up to 10 T) magnetic fields in the temperature range of 80–300 K, and the resistance-relaxation processes were studied after the switch-off of the magnetic pulse with an amplitude of 10 T and a duration of 200 μs. It was found that the high-field MR values were comparable for all investigated films (~−40% at 10 T), whereas the memory effects differed depending on the film thickness and substrate used for the deposition. It was demonstrated that resistance relaxation to the initial state after removal of the magnetic field occurred in two time scales: fast’ (~300 μs) and slow (longer than 10 ms). The observed fast relaxation process was analyzed using the Kolmogorov–Avrami–Fatuzzo model, taking into account the reorientation of magnetic domains into their equilibrium state. The smallest remnant resistivity values were found for the LSMO films grown on SiO2/Si substrate in comparison to the LSMO/Al2O3 films. The testing of the LSMO/SiO2/Si-based magnetic sensors in an alternating magnetic field with a half-period of 22 μs demonstrated that these films could be used for the development of fast magnetic sensors operating at room temperature. For operation at cryogenic temperature, the LSMO/SiO2/Si films could be employed only for single-pulse measurements due to magnetic-memory effects

Investigation of magnetoresistance and its anisotropy of thin polycrystalline La0.83Sr0.17MnO3 films in high pulsed magnetic fields / N. Žurauskienė, S. Keršulis, L. Medišauskas, S. Tolvaišienė.

The results on the study of grain boundary effects and influence of film deposition conditions on the magnetoresistance and its anisotropy in polycrystalline La0.83Sr0.17MnO3 films are presented. The magnetoresistance was measured in high pulsed magnetic fields up to 25 T (pulse duration approximate to 0.6 ms) in the temperature range of 120-300 K. A modified Mott hopping model was applied to describe the main behavior of high-field magnetoresistance for both ferromagnetic and paramagnetic phases of the polycrystalline films by taking into account the demagnetization field of the films measured in low magnetic fields perpendicular to film plane. It was also found that to obtain the higher magnetoresistance saturation field at room temperature it is necessary to use the films with smaller crystallites (D approximate to 100 nm). Such films could be used for design of megagauss pulsed magnetic field sensors

Concepts and Capabilities of In-House Built Nanosecond Pulsed Electric Field (nsPEF) Generators for Electroporation: State of Art

Electroporation is a pulsed electric field triggered phenomenon of cell permeabilization, which is extensively used in biomedical and biotechnological context. There is a growing scientific demand for high-voltage and/or high-frequency pulse generators for electropermeabilization of cells (electroporators). In the scope of this article we have reviewed the basic topologies of nanosecond pulsed electric field (nsPEF) generators for electroporation and the parametric capabilities of various in-house built devices, which were introduced in the last two decades. Classification of more than 60 various nsPEF generators was performed and pulse forming characteristics (pulse shape, voltage, duration and repetition frequency) were listed and compared. Lastly, the trends in the development of the electroporation technology were discussed.This article belongs to the Special Issue Electroporation Systems and Application

Microsecond electroporator optimization for parasitic load handling and damping

During development of the pulsed power generators the o ccurrence of the parasitic elements in the circuit is inevitable, which leads to appearance of overvoltage, overcurrent and waveform distortions. This work is focused on the optimization of the microsecond electroporator to enable handling and damping of the parasitic loads. The optimization is based on a flexible PSPICE model of the electroporator, which is used for the compensation of the parasitic parameters. Based on the modelling results the parameters and the circuit elements for the device are selected. The compliance of the prototype’s experimental and the PSPICE simulated output pulses is analysed. The optimized circuit of the microsecond electroporator is designed. The system supports current handling up to 100 A and capable to generate up to 4 kV square wave pulses

Modelling the cell transmembrane potential dependence on the structure of the pulsed magnetic field coils

During high power pulsed magnetic field treatment of biological samples the cells are subjected to both the high magnetic and induced electric fields. The extent of the influence of each treatment component is poorly studied. The work presents the finite element method analysis of pulsed inductive coils that are used for generation of pulsed magnetic and induced electric fields. The simulated coils, electrical parameters and the output characteristics are evaluated in respect to the induced cell transmembrane potential. The model of the Jurkat T lymphocyte cells is introduced in the analysis. The study includes finite element method analysis of four solenoid coils with different structure and inductance in the range of 2.8 μ H to 62 μ H. Pulsed magnetic field amplitudes up to 5 T are investigated in this work

Compact electro-permeabilization system for control led treatment of biological cells and cell medium conductivity change measurement

Subjection of biological cells to high intensity pu lsed electric field results in the permeabilization of the cell membrane. Measurement of the electrical conductivity change a llows an analysis of the dynamics of the process, determination of the permeabilization thresholds, and ion efflux influence. In this work a compact electro-permeabilization system for controlled treatment of biological cells is presented. The system is capable of delivering 5 μs – 5 ms repetitive square wave electric field pulses with amplitude up to 1 kV. Evaluation of the cell medium conductivity change is implemented in the set up, allowing indirect measurement of the ion concentration changes occurring due to the cell membrane permeabilization. The simulation model using SPICE and the experimental data of the proposed system are presented in this work. Experimental data with biological cells is also overviewed

Computer controlled thermostat for the resistivity measurements of the La1-xSrxMnO3 thin films

The temperature stabilization system for the magnetoresistance measurements of the La1-xSrxMnO3 manganites is described in this paper. The thermostat cell with the Peltier heating/cooling element was manufactured specially to be placed between the poles of the electromagnet. The heat sink attached to the rear side of the Peltier element is cooled by the flowing tap water. Platinum film temperature probe was used for the temperature feedback signal. Universal multimeter “Tektronix DMM 4050” was used as a temperature meter and a regulated laboratory power supply “TTI QL 564P” was used to supply the current through the Peltier element. Both instruments were controlled by the computer software via the USB and GPIB interfaces. The software implementing a PID algorithm was written in the LabView graphical programming interface. The results show that the temperature of the sample can be changed in 2-3 minutes depending on the temperature step and is kept constant with precision of ±0.02 °C

Experimental setup for magnetoresistance analysis of lanthanum manganites thin films

A measurement and automation equipment for measuring the manganite resistance dependence on magnetic field is designed and developed in this work. Equipment consists of the electromagnet, the programmable power source, the magnetic field meter and the resistance measurement device. All devices are connected to PC by the GPIB cables and the GPIB-USB converter. The control program was created by using the LabVIEW software package. It enabled to change the steps of the current through the electromagnet in different ranges of the magnetic field and to set desired measurement accuracy and duration. The system was used for measuring of the magnetoresistance of the manganites films dependence on the magnetic field. The accuracy, which was achieved using this equipment, allows calculating anisotropy of MR of the manganites films despite to small changes of the resistance at low magnetic field

Design and optimization of pulsed magnetic field generator for cell magneto- permeabilization

Biological cell magneto-permeabilization is the phenomenon when the membrane of the cell increases permeability to molecules to which it was initially impermeable due to the exposure to high pulsed magnetic fields. Flexible high power electronics systems are required for triggering this effect. In this work, we have designed a high power (938 A, 2 kV) pulsed magnetic field generator (up to 5.5 T), which generates 10 μs–100 μs pulses with predefined repetition frequency of 1 Hz–100 Hz. We have applied SPICE and COMSOL Multiphysics modelling for design and development of the system, which showed a good agreement with the experimental results. The snubber and crowbar circuitry has been implemented for compensation and dampening of the transient processes on the switches, which allowed limiting the overvoltage to 0.25 kV. The multilayer inductor structure and design considerations are also presented in the study