DISPOSITIVO DE INDUÇÃO MAGNÉTICA E CIRCUITO ELETRÔNICO

Description

1 / 34 Magnetic Induction Device and Electronic Circuit FIELD OF APPLICATION

[001] The present invention applies to the field of electromagnetism in the area of ​​engineering and biomedicine. More specifically, it is a magnetic induction device aimed at application to magnetic nanoparticles (MNPs), with the objective of heating them. FUNDAMENTALS OF THE INVENTION

[002] There are commercial magnetic induction devices that operate at higher frequencies and magnetic fields, which are desirable characteristics. However, they are based on very complex electronic circuits, making them expensive and impractical for some applications. Others use sophisticated and expensive equipment, which requires special care in terms of the operating environment and conditions.

[003] The use of a simple LC circuit, configured in parallel, presents significant limitations in terms of simultaneous variation of the magnetic field and frequency. In this type of configuration, resonance occurs with the lowest electric current, which limits the power generated. Furthermore, increasing the frequency results in an increase in inductive reactance, which decreases the alternating current flowing through the coil. At very high frequencies, the intensity of the magnetic field may become insufficient to generate heating in the NPMs. However, in the circuit developed in the present invention, these limitations have been effectively mitigated. The influence of these parameters on the magnetic field has been significantly reduced, proving to be lower when compared Petition 870250007014, dated 01 / 28 / 2025, page 10 / 53 2 / 34 both to studies previously published in scientific journals and to commercially available equipment.

[004] The main advantages of this system include low production cost, ease of modification in a laboratory environment, and versatility in adjusting the experimental configuration according to the specific needs of each experiment. These modifications can involve parameters such as the size, position, shape, and direction of the coil. This level of customization represents a significant advance for magnetic nanoparticle heating experiments, overcoming the limitations observed in commercial equipment, which is generally more rigid and less adaptable to experimental variations. STATE OF THE ART

[005] The document “Magnetic Induction Device For "Nanoparticles Heating At Frequency > 500 kHz" describes a magnetic induction hyperthermia device designed to raise the temperature in biological tissues above 42 °C, enhancing drug-based treatments to eliminate cancerous cells. The equipment operates at selectable frequencies between 85 kHz and 900 kHz, using a parallel LC resonant circuit with a self-resonant inverter coupled to a power supply. This configuration eliminates the need for external signal generators, making the device autonomous and portable. It generates a magnetic field of 0.44 mT to 5.11 mT and includes a built-in cooling system. The wide frequency range is the device's main differentiating factor. Petition 870250007014, dated 01 / 28 / 2025, page 11 / 53 3 / 34 higher than others reported in the literature, which are generally below 500 kHz.

[006] However, this invention presents significant differences, the first of which is in the coil configuration. The authors of the aforementioned document used a configuration in which the coil is connected to the source at its center, dividing it in two. This causes only half of the coil to function in each oscillation cycle. In one cycle, the current passes through the upper part of the coil. In the second cycle, the current passes through the lower part. As a result, there is a low magnetic field (maximum of 5.11 mT), responsible for generating a heating of only 8 °C. The second difference lies in the appropriate choice of electronic components, which were not carefully selected by the authors, limiting the current flow in their system. For example, the maximum current passing through the circuit was 29 A, while in the present device it can exceed 100 A. This exemplifies and reinforces the importance of using appropriate electronic components.The third difference lies in the operating voltage of the circuit, which was 15 V in the document, while in the present invention it is more than double (38 V). Finally, the operating time of the circuit proved to be very limited, at only 5 minutes, while in the present invention it reached 100 minutes of operation. This seems to be related to the cooling systems employed, which were not adequate and allow overheating in the circuit of the cited document.

[007] Document WO24079713 discloses a high-frequency magnetic induction device. The device includes a magnetic nanosuspension and a magnetic field generator. Petition 870250007014, dated 01 / 28 / 2025, p. 12 / 53 4 / 34 alternating current (AMF). The AMF generator consists of a copper induction coil, working head, flexible connector, power supply, cooler, control and display unit, fiber optic thermometer sensors, automatic / manual selector switch, USB ports, and bed support. The tumor site, enveloped by the magnetic nanosuspension containing magnetic iron oxide nanoparticles, generates heat when exposed to the AMF produced by the generator. This heat is precisely controlled, without causing damage to healthy tissues. The high-frequency induction device is safe, effective, non-invasive, and has mild side effects.

[008] However, the equipment presented in the document differs substantially from the current proposal, as it uses an alternating magnetic field generator and a commercial power source, without the development of its own electronic circuit. This approach implies high costs, making the equipment inaccessible to many research groups. The lack of detailed information in the document, such as the materials used in the construction of the induction coil (copper tube or sheet, number of turns, length), which may be unsuitable for industrial applications, the auxiliary equipment, and the intensity of the applied current (which must be high), makes it difficult to replicate the system, restricting its applicability. In addition, the equipment has limitations in terms of flexibility of experimental configuration and adaptation to different work environments, whose focus is on the treatment of cancerous cells.

[009] On the other hand, the equipment proposed in the present invention was designed with a focus on accessibility and Petition 870250007014, dated 01 / 28 / 2025, page 13 / 53 5 / 34 efficiency. It uses low-cost and easy-to-build components, allowing it to operate in considerable magnetic field and frequency ranges, with the capacity to perform prolonged experiments (up to 100 minutes). The system is also portable, robust, and suitable for use in harsh industrial and laboratory environments.

[0010] Another important differentiating factor is the optimized energy consumption. The equipment proposed in the present invention operates with a supply current of around 10 A, significantly lower than that estimated for the equipment presented in WO24079713. This characteristic results in superior energy efficiency, reducing operating costs and increasing viability for industrial and medical applications. Furthermore, the configuration allows for the efficient generation of heat for magnetic hyperthermia studies aimed at combating cancer, making the system an economically viable alternative for different applications.

[0011] Document WO11107290 describes how magnetic nanoparticles are used for radiological investigations, MRI, or as a therapeutic medium in magnetically induced hyperthermia. In all these biomedical applications, the metallic particles, with a size much smaller than 100 nm, possess magnetic activity. They are functionalized with biocompatible organic ligands, allowing the biological transport of the nanoparticles to specific areas. The magnetic particles are prepared by replacing the ligand with solvated metallic atoms in a solvent. The preparation method uses Metal Vapor Synthesis to produce metallic nanoparticles and Petition 870250007014, dated 01 / 28 / 2025, page 14 / 53 6 / 34 stabilize them with biocompatible ligands of different natures, such as glucose-stabilized iron nanoparticles. Furthermore, the internalization of these particles, especially glucose-stabilized iron nanoparticles, into neoplastic cells is noteworthy.

[0012] However, the document presented does not focus on the development of a magnetic induction heating device applicable to magnetic nanoparticles. The document is directed towards the development of a methodology capable of producing glucose-coated magnetic nanoparticles to provide a homogeneous particle size distribution, high stability, and high selectivity for specific cancer cells. On the other hand, the present inventors have shown that the size range is between 4 and 16 nm, a range that demonstrates heating efficiency in the proposed equipment. At the larger size, in particular, it has been shown that heating is more efficient in the present invention, proving its efficiency not only for industrial applications but also for medical applications.

[0013] Document MX2012003963 discloses a magnetic induction heating device for performing cell necrosis tests or measuring specific absorption rate. The device has an adjustable frequency pulse generator, whose signal is amplified by a current inverter powered by an adjustable DC source. This generator includes a full H-bridge with four transistors connected in a series capacitor-inductor configuration, which attenuates high frequencies from the amplifier pulses and eliminates frequency levels. Petition 870250007014, dated 01 / 28 / 2025, page 15 / 53 7 / 34 null. It powers a resonant circuit with a capacitor and inductor in parallel, the inductor being called the working coil, designed to generate a magnetic field region in an adiabatic medium where a sliding tray containing a container holding the sample to be analyzed is located. The device includes two replaceable working coils for testing with test tubes or Petri dishes, depending on whether the materials analyzed are cell cultures subjected to necrosis by thermotherapy via magnetic particles. The invention also features an interactive interface for operation, means of communication for computer-based automation, and a liquid cooling system for the components.

[0014] However, the document uses a full H-bridge of transistors, responsible for switching between the different transistors and allowing an alternating current in the working coil. In comparison, the circuit disclosed in the present invention uses a half H-bridge, which significantly reduces the complexity of the circuit, the number of components and manufacturing costs, in addition to providing greater ease of operation. The result is a more compact device, with lower heat dissipation, high efficiency at high frequencies, less electromagnetic interference and excellent performance in low power applications.

[0015] Therefore, it can be concluded that the present invention differs from the prior art documents presented here, since none of them refers to a magnetic induction heating device that combines an optimized half-H-bridge configuration to reduce Petition 870250007014, dated 01 / 28 / 2025, p. 16 / 53 8 / 34 complexity and costs, ability to generate high magnetic fields (up to 23.6 mT) with currents exceeding 100 A, precise thermal control through an efficient thermal bath operating at extreme temperatures (-25 °C to 23 °C), and a compact and safe design with advanced PCB and insulation, in addition to operating stably and continuously for up to 100 minutes, which is essential for prolonged and high-precision experiments. SUMMARY OF THE INVENTION

[0016] The present invention describes a magnetic induction device developed for heating magnetic nanoparticles (MNPs), notable for adapting a simple and accessible electronic circuit for high-frequency and high-current applications. Designed to overcome limitations of commercial equipment, the device integrates a parallel LC circuit with zero-voltage switching (ZVS) technology, allowing for greater energy efficiency and reduced losses. With components such as polypropylene capacitors, high-current MOSFET transistors, and optimized coils, the equipment achieves a magnetic field of up to 23.6 mT and frequencies between 50 and 200 kHz, being able to operate stably for up to 100 minutes thanks to its strategic cooling systems.

[0017] The invention offers significant advantages, including low production cost, flexibility for experimental adjustments, and portability. Its compact and configurable design allows for applications in different contexts, especially in the biomedical field, such as magnetic hyperthermia treatments against cancer. Furthermore, the Petition 870250007014, dated 01 / 28 / 2025, page 17 / 53 9 / 34 equipment was designed to be robust, efficient, and affordable. BRIEF DESCRIPTION OF THE FIGURES

[0018] The invention can be better understood through the brief description in the following figures: Figure 1 shows the electronic circuit diagram used in the magnetic induction device using the LTspice software, where C1 corresponds to the total capacitance of the capacitor bank. Figure 2 shows the simulations performed in the LTspice software, where (a) shows simulated voltage signals on both sides of coil 1 in blue and green, while in (b) the current is shown in purple. Figure 3 shows the voltage measurements (a) on both sides of coil 1 with an oscilloscope and (b) shows the current calculated in the coil with the TRF showing that the system operates only at the resonance frequency (52 kHz). Figure 4 shows the electronic characterization of the system signal, with the voltage (a) and current calculated in the coil (b) with the TRF showing that the system operates only at the resonance frequency (64.4 kHz). Figure 5 shows the heating curves of iron oxide nanoparticle suspensions at different concentrations at (a) 52.2 kHz and Bmax = 23.6 mT, (b) 93.9 kHz and Bmax = 12.9 mT, and (c) 17 6.5 kHz and Bmax = 8.3 mT with coil 1. Figure 6 shows (a) the heating curves of iron oxide nanoparticle suspensions at different concentrations and (b) the ice melting experiment. Petition 870250007014, dated 01 / 28 / 2025, page 18 / 53 10 / 34 with 1 mg / mL. The frequency and maximum magnetic induction field are 81.9 kHz and 21.5 mT, respectively. Figure 7 shows (a) an image of the droplets with NPMs clustered inside and (b) the droplet size distribution measured using the free software ImageJ. Figure 8 shows (a) heating curves for emulsions E1, E2 and E3 at 81.9 kHz and 21.5 mT and (b) figures of the emulsions after a few minutes of agitation, highlighting the particles deposited in system E3. Figure 9 shows the temperature variation curves of Pickering emulsions with NPMs@Silane in different aqueous phase ratios for MNP@Silane (v / v) of (a) 1:1, (b) 1:2 and (c) 1:3. The CMA operates at 64.4 kHz and 16.9 mT. Figure 10 shows the temperature variation curves of systems PE7, PE8, and PE9 at 64.4 kHz and 16.9 mT, where the initial temperature of the experiments was -4.5 °C. Figure 11 illustrates the magnetic induction device. DETAILED DESCRIPTION OF THE INVENTION

[0019] The invention can be better understood through the following detailed description, in accordance with the attached figures.

[0020] The present invention describes a magnetic induction device developed for heating magnetic nanoparticles (MNPs), notable for the adaptation of a simple and accessible electronic circuit for high frequency and current applications. The circuit used comprises a parallel LC configuration, as illustrated by the diagram in Figure 1, which was first simulated using the LTspice software. This configuration incorporates a self-resonant circuit based on Petition 870250007014, dated 01 / 28 / 2025, page 19 / 53 11 / 34 in the Zero Voltage Switching (ZVS) system, enabling "smooth switching" between the two MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors). This system significantly reduces energy losses during on-off transitions at high frequency and high power. This interesting feature offers potential for applications involving NPMs.

[0021] The electronic circuit (IC) is powered by a 12 V, 100 A DC power supply (Mei Shi Le Technology Co.). This circuit is composed of simple and low-cost components, making its construction easy. To protect the rectifier diodes (D3 and D4) and the MOSFET transistors (M1 and M2), the resistors (R1 and R2), connected to the power supply, reduce the current and control the voltage at the transistors' gate, ensuring their safe operation. To prevent fluctuations in both voltage and current at the gate, the resistors (R3 and R4) are connected to the Zener diodes (D1 and D2), which also protect these diodes from reverse currents. The Zener diode connected to the transistor's source-gate provides additional protection by regulating the voltage drop and draining any excessive current caused by power surges.Toroidal inductors (L1 and L2) prevent the system frequency from returning to the power supply, control high-frequency power surges, and reduce system noise. On the other hand, diodes D3 and D4 are responsible for rectifying and draining the small current that reaches the "gate" of MOSFETs M1 and M2 towards the working coil (L3), also preventing parasitic currents that damage the transistors. Petition 870250007014, dated 01 / 28 / 2025, p. 20 / 53 12 / 34

[0022] The power supply provides power to transistors M1 and M2, which are responsible for the oscillation in the circuit. They also regulate the current flowing through the coil according to their specifications. The oscillation occurs due to the sequential activation and deactivation of MOSFETs M1 and M2. In each half-cycle of oscillation, one MOSFET is activated while the other remains off. This alternation between the transistors is regulated by the rectifier diodes (D3 or D4), which connect the gate of one MOSFET to the drain of the other. To ensure optimal and long-term operation, three cooling arrangements were employed (Figure 11). The first comprises a small commercial water pump immersed in a water container. This pump is connected to aluminum blocks (BA) via a silicone hose, which in turn are in contact with transistors M1 and M2. The purpose of this cooling arrangement is to dissipate the heat generated in MOSFETs M1 and M2 to maintain the temperature within acceptable limits. The second cooling arrangement was designed to cool capacitors C1 which, like the transistors, experience intense heating when operating at high power and high frequency. This arrangement comprises the use of three high-speed fans (V) (5000 rpm) to prevent the capacitors from burning out. The third arrangement was used to cool the coil and prevent excessive heating due to the Joule effect, which can overheat the system inside the coil.Initially, a second aquarium pump was used in a bucket containing a significant amount of ice and water. The design calculations showed that this was sufficient for the system inside the coil. Petition 870250007014, dated 01 / 28 / 2025, page 21 / 53 13 / 34 remained without appreciable temperature variation. Subsequently, a thermal bath was used to ensure meticulous temperature control in the coil and allow application at temperatures below 0 °C. The specifications of each component are described in the following table. Table 1 - Electronic components used and their specifications Abbreviation Component Specification L1 and L2 Toroidal inductors 50 μH, 10 A / 10 μH, 20 A R1 and R2 Resistors 470 Ω / 5 W D1 and D2 Zener diode 1N5349B 5W / 12V M1 and M2 MOSFET transistors IRF1704, 170 A D3 and D4 Rectifier diodes IN4007 1 A / 1000 V R3 and R4 11 Resistors Metallized film polypropylene capacitors 10 kΩ / 0.5 W 105MPR250K 1 μF (10%) / 650 VDC

[0023] The resonance tank comprises a bank of parallel capacitors (C1) also connected in parallel to the working coil (L3), which determines the operational resonance frequency (Equation 1). (1)

[0024] Where L is the inductance of the coil (H) and C is the total capacitance of the capacitor bank (F). Two different coils were produced with different internal diameters (di), number of turns (N) and length (l), Petition 870250007014, dated 01 / 28 / 2025, p. 22 / 53 14 / 34 resulting in different frequencies (Hz) and maximum magnetic field (BMAX). It is important to emphasize that, for applications in heating nanoparticles by magnetic induction, the aim is to optimize this circuit to operate with maximum magnetic field. To determine the appropriate capacitance and number of capacitors for a given frequency range, Equation (2) can be applied. Polypropylene metallized film capacitors were chosen due to their good stability, high insulation resistance, and high storage capacity. Since the circuit is configured in parallel LC, the maximum current in coil (II) was calculated using equation 2. ILLXl (2)

[0025] Where Xl (= 2nfL) is the inductive reactance of the coil, measuring the peak voltage in the coil (VL) with an oscilloscope (model RIGOL DS1074Z), also used for visualization and characterization of the waveform.

[0026] The maximum intensity of the magnetic induction field inside the coil depends on the magnetic permeability of the material inside it (μ). Considering air, the magnetic permeability will be μ0 (4m10-7Tm / A). Then: (3)

[0027] The limitation of the parallel circuit is that, at the resonance frequency, the impedance is maximum, which Petition 870250007014, dated 01 / 28 / 2025, p. 23 / 53 15 / 34 means that the current will always be minimal. According to equation 2, it can be observed that as feL increases, the current in the coil decreases. Since the inductance of the coil is given by: μοΝ2A (4)

[0028] Applying equations (2) and (4) to Equation (3), we find the equation that describes the magnetic field in the coil for a parallel LC circuit. _ Vl 2nfAN (5)

[0029] The equation above allows us to conclude that increasing the number of turns in the coil reduces the magnetic field. Therefore, in the case of a parallel configuration, it is better to decrease the number of turns and increase the supply voltage. Furthermore, increasing the frequency and the area (A) of the coil will also result in a decrease in the magnetic field. Similarly, for the same coil (constant L), increasing the frequency will lead to a reduction in the magnetic field. Additionally, to improve the homogeneity of the magnetic field within the coil, thicker copper tubing can be used, since, according to Equation (5), the intensity of the magnetic field does not depend on the length of the coil. It is important to note that Equation (5) represents an ideal equation, and since the coil is far from ideal, it cannot be used to precisely calculate the maximum induction magnetic field. Petition 870250007014, dated 01 / 28 / 2025, page 24 / 53 16 / 34

[0030] In this sense, three different coils were manufactured using copper tubes. Coil 1 was constructed using copper tubes with inner and outer diameters of 2.5 and 3.5 mm, respectively. Coils 2 and 3 were made with copper tubes with inner and outer diameters of 5 and 6.35 mm, respectively. The specific dimensions are described in Table 2. To determine the coil's inductance, measurements of the total capacitance and the resonant frequency were performed. Equation 4 was then used to calculate the inductance value. It is important to note that the calculated inductance may differ from the value obtained using Equation (4) due to small imperfections and distortions in the handmade coils. An important feature of the proposed system is that it is compact, portable, the frequency can be changed by changing the capacitor bank, and the coil can be swapped according to the experiment's configuration. Table 2 - Specifications of the constructed coils: length (l), inner diameter (di), number of turns (n), and inductance calculated by Equation 2. Specifications Coil 1 Coil 2 Coil 3 l (mm) 22.4 31.0 32.6 di (mm) 28.0 33.0 29.65 n 8 4 4 L (μΗ) 1.1 0.472 0.611 Characterization of the electronic circuit

[0031] The waveform and voltage amplitude in the working coil (L3) were analyzed using an oscilloscope. Different frequencies between 50 and 200 kHz were tested and compared with simulations in LTspice. Figure 2 shows the simulated voltage signal for the empty coil 1 and the voltage supplied by the power supply, with an inductance of 1.1 Ω. Petition 870250007014, dated 01 / 28 / 2025, page 25 / 53 17 / 34 μH and a frequency of 52.2 kHz. Initially, the signal exhibits a high-amplitude oscillation (not shown), but stabilizes at 36.41 V after a few microseconds. Two positive half-cycles of sinusoidal waveforms can be observed, resulting from measurements on both sides of the coil relative to the negative pole of the power supply, causing a 90° phase shift between the positive half-cycles. The simulations in Figure 2 also show the current, which initially reaches a high peak value (not shown) and stabilizes at 99 A after a few microseconds. Unlike the voltage, the current exhibits a complete sinusoidal waveform, confirming the presence of an oscillating current in the coil. Analysis of the peak values ​​for voltage and current revealed a 90° phase shift between the two signals.This result is consistent with the theoretical behavior of an inductor and indicates an efficient energy exchange between the capacitors and the inductor of the present electronic device, consistent with the literature.

[0032] Figure 3 shows the voltage signal measured on both sides of the coil using an oscilloscope and the calculated current waveform. The same 90° phase shift between the two half-cycles is observed for both amplitude (38 V) and current (105 A), demonstrating excellent agreement between the simulations and measurements in terms of voltage and current values.

[0033] For a more in-depth characterization, the The Fast Fourier Transform (FFT) of the voltage signal was calculated to analyze the Total Harmonic Distortion (THD). The THD quantifies the total distortion caused by superposition. Petition 870250007014, dated 01 / 28 / 2025, page 26 / 53 18 / 34 of harmonics, which are frequencies that are multiples of the main frequency in the alternating current signal. However, the THD was considered insignificant, as no overlap of other frequencies was observed, indicating a high-quality signal with only one sharp peak at the resonance frequency (Figure 4b). Equations 2 and 3 were applied to calculate the maximum intensity of the induction magnetic field for the coils used at different frequencies. For coil 1, Bmax was 23.6 mT at 52.2 kHz. It is worth noting that the voltage across the coil is almost three times the supplied voltage (12 V), which is a characteristic of this type of circuit. It should also be noted that the results obtained for the frequencies of 93.9 kHz and 12.9 mT and 176.5 kHz and 8.3 mT with coil 1 showed a very similar behavior, close to the simulations. The same can be said regarding coil 2, whose circuit was the same as that used for coil 1 (Figure 3), with only the coil being changed.

[0034] The characterization of the final system is presented in Figure 4. It can be observed that the final system presents lower maximum voltages and currents compared to the initial system. This can be attributed to two factors. The first is the use of toroidal coils in the circuit. In the initial case, 100 μH coils were used, while in the final system these coils were reduced to only 10 μH, which reduced the final voltage on the working coil. The second factor is the significant heating of the PCB (Printed Circuit Board), which dissipates part of the electrical energy in the form of heat. Therefore, high-speed fans (V) (5000 rpm) were needed to maintain the temperature around 100°C. Despite the lower magnetic induction field in the Petition 870250007014, dated 01 / 28 / 2025, page 27 / 53 With the 19 / 34 coil, the system became much more organized and safer to operate. Furthermore, as shown in Figure 5, both voltage and current maintained a clean, low-noise signal, ensuring high signal quality, since the FFT exhibited a single peak at the resonant frequency of 64.4 kHz and the maximum magnetic field reached 16.9 mT. Heating experiments in suspensions of iron oxide nanoparticles (IONPs)

[0035] Suspensions of magnetic nanoparticles were prepared by weighing a specific mass of iron oxide nanoparticles and adding deionized water to obtain concentrations of 1, 3, 5, and 10 mg / mL. The mixture was then sonicated for 15 minutes at 35 kHz using a Symphony ultrasonic cleaner to disperse the nanoparticles, and allowed to reach room temperature before starting the experiment. To measure the temperature, an alcohol thermometer was placed in the center of the flask containing the nanoparticle suspension, and the temperature was recorded at 30-second intervals. In the experiments with coil 1, a 5 mL beaker with 5 mL of the sample was placed inside the coil. For coil 2, glass flasks with mL of the respective samples were used. The temperature variation over time was measured twice for each sample.

[0036] The SAR (Specific Absorption Rate) value was determined using Equation (6), considering the specific heat capacity (Cp) of water for all nanoparticle suspensions, since the contribution of the nanoparticles to the total Cp value is negligible. Additionally, an ice melting experiment was performed. Approximately 14 g of ice and 4 g of water were Petition 870250007014, dated 01 / 28 / 2025, page 28 / 53 20 / 34 were placed in a 20 mL flask, and 2 mL of the 10 mg / mL suspension were added to achieve a concentration of approximately 1 mg / mL. Insulating foam was used to prevent heat loss during the experiments, insulating the container inside the coil. Additionally, a second layer of insulation was applied around the coil to further increase insulation efficiency. To ensure effective cooling of the coil and transistors, a significant amount of ice was placed in the buckets that served as reservoirs for the cooling systems, maintaining the coil temperature close to 0 °C during the experiment and preventing overheating of the transistors. SAR = mcpdTmMNPdt(6)

[0037] Where mcp is, respectively, the mass and specific heat of the sample, mmNP is the total mass of the magnetic nanoparticles and dT / dt is the initial slope of the temperature variation as a function of time, which can be determined by the calorimetric method.

[0038] Heating experiments were performed using iron oxide nanoparticle suspensions at room temperature (20 °C). Figure 5 shows the ΔT x t curves at different concentrations, using coil 1 under three different FeH conditions. Clearly, increasing the concentration of magnetic nanoparticles (MNPs) leads to an increase in ΔT for all FeH conditions. The most significant temperature increase was observed at 52.2 kHz and 23.6 mT for a concentration of 10 mg / mL (Figure 10). In this Petition 870250007014, dated 01 / 28 / 2025, p. 29 / 53 In case 21 / 34, the temperature reached 55 °C in 10 minutes. These results indicate that the system is well-suited for hyperthermia studies and can rapidly reach the therapeutic temperature range (42-46 °C) in a few minutes. Therefore, the proposed device shows promising potential for efficient applications in hyperthermia treatments.

[0039] The maximum specific absorption rate (SAR) of 60.6 ± 4.1 W / g was observed in the 1 mg / mL suspension, with a frequency of 52.2 kHz and a magnetic field of 23.6 mT. On the other hand, the minimum SAR of 5.7 ± 0.4 W / g was found at a concentration of 10 mg / mL, with a frequency of 176.5 kHz and a magnetic field of 8.3 mT. Although SAR is a significant parameter for comparison, it does not dictate the greater final temperature variation of the experiment, according to the results in Table 3. This discrepancy is attributed to the faster magnetization response of the nanoparticles in dilute systems with weaker dipolar interactions. In contrast, concentrated systems, despite releasing less heat per nanoparticle, compensate with more particles releasing heat collectively. Thus, an increase in the SAR value does not necessarily correspond to a greater temperature variation.This highlights the importance of considering overall heat generation efficiency, in addition to SAR values, when determining optimal conditions for specific applications. Table 3 - SAR values ​​for different concentrations and AMF conditions measured on coil 1 and coil 2. C (mg / mL) Coil 1 Coil 2 Petition 870250007014, dated 01 / 28 / 2025, page 30 / 53 22 / 34 52.2 kHz, 23.6 mT 93.9 kHz, 12.9 mT 176.5 kHz, 8.3 mT 81.9 kHz, 21.5 mT 1 60.6 ± 4.1 17.8 ± 2.7 8.4 ± 2.9 15.2 ± 1.1 3 26.9 ± 8.1 16.8 ± 1.6 6.9 ± 1.3 8.9 ± 1.9 5 41.6 ± 4.2 17.8 ± 0.1 6.2 ± 0.1 12.4 ± 1.3 10 27.5 ± 1.1 11.7 ± 1.3 5.7 ± 0.4 25.8 ± 1.2

[0040] From Figure 5, it is evident that as the frequency increases, the temperature variation decreases. This observation is consistent with the SAR values ​​obtained, which were 27.63 W / ga at 52.2 kHz and 23.6 mT. At 93.9 kHz and At 12.9 mT, the SAR value was 11.78 W / g, while at 176.5 kHz and 8.3 mT it was 5.68 W / g, for a concentration of 10 mg / mL. For iron oxide nanoparticles with a diameter of 15.73 nm, the ideal frequency can be expected to be around 97 kHz, using the relation 2π / τβ^ = 1, as predicted by Linear Response Theory (LRT). According to LRT, the dissipated power (P) in W / g of magnetic nanoparticles (MNPs) can be calculated using equation 7.

[0041] Where χx is PoXofH2 4π 2KfTef \ \1 + (2rcfTe / ·)2 / (7) equilibrium magnetic susceptibility (emu / gOe) eTef is the effective relaxation time, given by: (8)

[0042] rey has the contribution of Néel and Brown, which occur simultaneously, and which is dominated by Petition 870250007014, dated 01 / 28 / 2025, p. 31 / 53 23 / 34 shorter relaxation time mechanism. The Néel (τN) and Brown (τB) relaxation times of individual and isolated magnetic nanoparticles can be calculated as follows: Tç2J ^kBT KefV KefV e'A (9) _3rçyHτΒkBT (10)

[0043] Where τ0 is the characteristic relaxation time (109s) and η is the viscosity of the medium (8.9x10-4 Pa.s), considering the hydrodynamic volume (t#) equal to the average volume of the particle. In this case, the Brownian mechanism dominates the relaxation loss (τB< τN) according to equations 9 and 12.

[0044] However, considering that the nanoparticles are in the blocked state, hysteresis loss becomes the main mechanism responsible for heat release. Power dissipation, in this case, is quantified by the product of the hysteresis area and the frequency (P = Af). Theoretically, increasing the frequency should increase power dissipation. However, as mentioned earlier, in the present system the magnetic field is reduced as the frequency increases (Equation 6), which considerably reduces the hysteresis area. Therefore, it can be concluded that, for iron oxide nanoparticles around 16 nm, the device performs better at lower frequencies.

[0045] To further demonstrate applicability, the same heating experiments were performed with the Petition 870250007014, dated 01 / 28 / 2025, page 32 / 53 A 24 / 34 coil 2 was heated at 81.9 kHz and 21.5 mT for 30 minutes. The corresponding ΔT vs. t curves are shown in Figure 6 and exhibit similar behavior to the curves shown in Figure 5, where ΔT also increases with increasing concentration. For a concentration of 10 mg / mL, the maximum temperature change was reached around 22 minutes, with a final temperature of 93 °C. After that, the temperature remained constant, and as evaporation was observed, the experiment was terminated at 25 minutes. This indicates that the system can reach high temperatures. Additionally, a mixture of ice and water was heated with a concentration of ~1 mg / mL, as shown in Figure 6. Initially, the temperature remained practically constant for about 10 minutes, as the heat generated was mainly used to melt the ice. After this period, the temperature increased consistently, resulting in a final ΔT of 12 °C after 100 minutes.These results demonstrate the system's versatility, its ability to reach high temperatures with NPMs, and its effectiveness in prolonged experiments. Heating experiments with magnetic nanoparticles (MNPs) in water droplets

[0046] Suspensions of NPMs in water with concentrations of 5 and 20 mg / mL, prepared as described above, were mixed with decane and Span80 emulsifier (1% w / v) to prepare 20 mL W / O emulsions with 10% water cutoff and final NPM concentrations of 0.5, 1, and 2 mg / mL. The Mechanical Vortex mixer applied intense vibration (n° 8 / 10) for 10 minutes. The droplet size distribution (DSD) was measured using an optical microscope and the curves of Petition 870250007014, dated 01 / 28 / 2025, page 33 / 53 25 / 34 heating elements were produced at 81.9 kHz and a 21.5 mT alternating magnetic field for 30 minutes.

[0047] The induction heating process in emulsions was also studied. Immediately after emulsion preparation, the droplet size distribution was measured using an optical microscope. Figure 7-a shows the spherical droplets and the agglomerates of iron oxide nanoparticles within the droplets. In many droplets, it was not possible to observe the agglomerated NMPs, indicating that the particles were poorly dispersed in the liquid. This is attributed to the lack of a surface agent to stabilize the particles. Furthermore, a relatively wide droplet size distribution was measured, with an average size of 6.86 µm, as shown in Figure 7b, fitted with the log-normal distribution function. The droplet size distribution of the three prepared emulsions was very similar, demonstrating that the NMP concentration has a negligible influence on droplet size in the working range. Therefore, Figure 7-b can be considered representative for these emulsions.

[0048] The heating curve for the three emulsions is shown in Figure 8-a, performed in triplicate. Clearly, with increasing concentration, the temperature change also increases. The largest temperature variation (~18 °C) was observed for E3 with an MPN concentration of 2 mg / mL, followed by E2 (~13 °C) and E1 (~5 °C). However, Figure 8-b provides interesting information. First, after a few minutes, the drops settled at the bottom of the flask. Since the temperature was measured with an alcohol thermometer at half the height of the liquid, the temperature inside the drops is expected to be higher than measured. Second, the Petition 870250007014, dated 01 / 28 / 2025, p. 34 / 53 26 / 34 NPMs within the droplets are exposed to a considerably lower AMF intensity compared to the maximum value of 21.5 mT, meaning the heating process can be more extensive. Third, in emulsion E3, particles detached from the droplets and adhered to the bottle wall, while this was not observed in emulsions E1 and E2. Therefore, it is important to maintain a low concentration of NPMs to prevent particles from detaching from the droplets, which can lead to inorganic deposition, corrosion, and even pipe clogging. Furthermore, this highlights the importance of using coating agents to stabilize NPMs, preventing them from detaching from the droplets and ensuring better homogeneity of particle concentration within individual droplets. Heating experiments in Pickering emulsions

[0049] Pickering water-in-decane (W / D) emulsions were prepared using a mechanical homogenizer at 24000 rpm for 10 minutes. Water cutoff (α) of 10, 20, and 30% (v / v) with ratios of 1:1, 1:2, and 1:3 of H2O to MNP@Silane (v / v) were established to study the effect of water cutoff and MNP@Silane concentration on the induction heating process at room temperature (23 °C). These values, as well as the final MNP@Silane concentration (C f) considering the total volume of the emulsion (15 mL), are listed in Table 1. 4. Heating curves were produced in triplicate on the final induction equipment operating at 64.4 kHz and 16.9 mT alternating magnetic field. For comparison, PE 10 was prepared similarly to PE 2, but heated using a cement heating plate instead of MIHP to check for possible differences in results between the different heating processes. Petition 870250007014, dated 01 / 28 / 2025, page 35 / 53 27 / 34 Table 4 - W / D values ​​of Pickering emulsions. α (%) H2O to Emulsion Ratio Cf (mg / mL) (v / v) MNP@Silane PE 4 1.09 1:1 1.09 PE 5 2.18 1:1 2.18 PE 6 3.27 1:1 3.27 PE 1 2.18 1:2 2.18 PE 2 4.36 1:2 4.36 PE 3 6.54 1:2 6.54 PE 7 3.27 1:3 3.27 PE 8 6.54 1:3 6.54 PE 9 8.2 1:3 8.2 PE 10 4.36 1:2 4.36

[0050] At the appropriate silane concentration, NPMs can be slightly hydrophobic, with a contact angle close to 90°, making them suitable for the preparation of Pickering emulsions. The average heating curves performed in triplicate for these Pickering emulsions applying an alternating magnetic field (AMF) of 64.4 kHz and 16.9 mT at 23 °C are shown in Figure 9. It should be noted that these experiments were performed on the final equipment using coil 3.

[0051] The heating curves in Figure 9 show that, by increasing the water cutoff in the same H2O to NPM@Silane ratio, the heating also increases, since the final NPM concentration also increases (Table 4). The same Petition 870250007014, dated 01 / 28 / 2025, page 36 / 53 28 / 34 behavior is observed when maintaining a constant water cutoff but increasing the NPM@Silane to H2O ratio. The greatest heating is observed in PE 9, with 25% water and a 1:3 ratio of H2O to NPM@Silane, whose temperature varied by approximately 24 °C after 30 minutes, reaching °C. When comparing emulsions with different water cutoffs and different H2O to NPM@Silane ratios, a slightly greater heating is observed in emulsions with a higher water cutoff. For example, the temperature variation for PE 6 (30%) and PE 7 (10%) (both with a final concentration of NPM@Silane (3.27 mg / mL) was 9 and 7 °C, respectively. This occurs due to the precipitation of water droplets, where the magnetic field is weaker than at the center of the coil. Therefore, by increasing the water cutoff, the droplet bed has a greater height, causing the NPMs to experience a more intense magnetic field and release more heat. It is important to mention that the temperature measurement was taken at the center of the flask. As the droplets precipitate, the temperature at the bottom is higher. Comparing PE 4 and PE 9, the temperature difference between the bottom and the center of the flask was 1.5 and 13 °C, respectively. These experiments show consistent results and demonstrate that the developed equipment does, in fact, generate good results when applying NPMs. Furthermore, it allows for studies with innovative applications. For example, the results show that the induction heating process can be very efficient in preventing the formation of hydrates, a serious problem faced in the petroleum industry.

[0052] An unexpected effect was the substantial heating observed in the PCB of the final equipment. This heating Petition 870250007014, dated 01 / 28 / 2025, p. 37 / 53 29 / 34 showed intense and varied sample temperature within the coil in experiments conducted at negative temperatures. This effect, however, can be avoided by using a stronger thermal bath with a higher flow rate, capable of removing the heat from the coil generated by the Joule effect. Another point of attention was the significant reduction of the magnetic field for a nearby frequency in experiments using coils 2 and 3. This occurs due to the large heat dissipation that occurs in the PCB, especially near the coil. This can be resolved in different ways, such as using a more efficient cooling system than the fans used to dissipate heat in the capacitors and PCB. Despite this, it should be noted that the experiments still proved very promising, generating substantial heating in the frozen Pickering PE7, PE8, and PE9 emulsions. The result of the heating initiated at -4.5 °C in these systems is shown in Figure 10.

[0053] The results shown in Figure 10 highlight a direct correlation between nanoparticle concentration and temperature increase. The blue curve corresponds to an emulsion prepared with Span80, serving as a reference. Since this emulsion does not contain NPMs, there should be no significant temperature fluctuation. The variation of approximately 7.5 °C after 60 minutes is attributed to the intense electric current flowing through the printed circuit board (PCB), whose temperature reached 100 °C due to the Joule effect. Therefore, a powerful cooler is necessary to maintain a constant coil temperature after system activation.

[0054] On the other hand, Pickering emulsions containing NPMs exhibit a considerably more pronounced temperature increase compared to the blue curve. Furthermore, a Petition 870250007014, dated 01 / 28 / 2025, page 38 / 53 A 30 / 34 increase in MNP@Silane concentration results in a steeper curve slope and a higher final temperature. The most substantial temperature variation observed is approximately 20 °C at PE 9. A distinct change in the curves is noticeable with a small temperature increase near 0 °C, as thermal energy is primarily used for ice melting. This observation is attributed to the systems not being homogeneous and to the delay in heat transfer from the frozen droplets at the bottom of the flask to the middle of the oil phase, where the temperature was measured. The green curve, with a higher concentration, shows this phase transition region considerably smaller than the black and red curves. The phase transition ceased at 39 minutes for PE 7, at 33 minutes for PE 8, and at 15 minutes for PE 9, while for the system without NPMs the phase transition ended at 50 minutes.Despite the observed Joule heat effect, these preliminary results show that NPMs can significantly reduce the ice melt transition time and demonstrate the promising role of NPMs in NGH dissociation during oil production.

[0055] Commercial magnetic induction equipment often has several limitations. They are usually expensive, bulky, and have limited flexibility regarding coil configuration. Furthermore, this equipment is designed to work with small sample volumes and requires a dedicated power line that can draw currents on the order of 600 A at high voltages, posing a significant risk to operators. Additionally, the duration of experiments in Petition 870250007014, dated 01 / 28 / 2025, page 39 / 53 31 / 34 commercial equipment is often limited to approximately 30 minutes due to heating and electrical stress on the components.

[0056] The proposed device features several innovations that differentiate it from existing commercial models. First, the proposed device is more accessible and has a reduced cost, making it a more viable option for a wider range of users. Operation is simplified, and the portable design not only allows for adjustment of the coil configuration as needed for different experiments, but also facilitates transport to industrial environments and confined spaces. This expands the possibilities for applying the equipment in different contexts and workplaces.

[0057] In addition, the equipment is capable of handling larger sample volumes, increasing its versatility in practical applications. Maintenance is simpler and involves cheaper components that the operator can easily identify and replace. Operator safety is a priority, as the circuit operates at low voltages (< 40V), minimizing the risks associated with high voltage levels.

[0058] Additionally, the proposed equipment stands out for its ability to perform experiments for much longer periods, lasting up to 100 minutes, as demonstrated by previous results. This extended operating time is a significant advantage compared to commercial equipment, which often has limitations in this respect. Petition 870250007014, dated 01 / 28 / 2025, pages 40 / 53 32 / 34

[0059] In terms of performance, the circuit generates a voltage in the coil almost three times higher than the supplied voltage (12 V), which represents a significant advantage over circuits described in the literature. For example, Cano et al. (3) proposed a circuit with four transistors in an H-bridge configuration, achieving a peak current of 29 A and a maximum voltage of 100 V, with a Bmax of approximately 15 mT. Plascencia-Cruz et al. (2) developed a parallel LC circuit that operates between 85 and 900 kHz, but with a limited magnetic field (BMAX = 5.11 mT) and a temperature variation of only 8 K after 5 minutes of testing with magnetite nanoparticles.

[0060] In comparison, Neto et al. (4) reported a SAR of W / g under similar conditions (62 kHz and 20 mT) using Fe3O4 NPs coated with sodium oleate at 50 mg / mL. The SAR values ​​presented by the present experiments are higher and comparable to those reported by Lemine et al. (5), who observed a SAR of 84.28 W / g at the same concentration at 332.8 kHz and 17 mT. The maximum temperature observed in the present experiments was 80.79 °C at a concentration of 10 mg / mL, which is higher than that observed in similar studies and demonstrates the ability of our equipment to operate under more extreme conditions.

[0061] These innovations highlight the proposed equipment as a more accessible, safe and efficient solution for magnetic induction of nanoparticles, with superior capabilities in terms of adjustment, maintenance and performance, and also offer the flexibility to be transported to different industrial and space-limited environments, compared to existing commercial equipment. Petition 870250007014, dated 01 / 28 / 2025, pp. 41 / 53 33 / 34

[0062] The present invention has been disclosed in this descriptive report in terms of its preferred embodiment. However, other modifications and variations are possible from the present description, and are still within the scope of the invention disclosed herein. REFERENCE SIGNS IC — Electronic Circuit L1, L2 - Toroidal Inductors L3 - Working Coil R1, R2, R3, R4 - Resistors D1, D2 - Zener diodes D3, D4 - Rectified diodes M1, M2 - MOSFET Transistors C1 - Parallel capacitor bank BIBLIOGRAPHIC REFERENCES 1. Morgan VG, Sum AK, Wu N, Dante A, Gomes AMS, Ferreira LS, Gomes SF, Werneck MM, Allil RCSB 2024 Development of an experimental device for inductive heating of magnetic nanoparticles Meas. Sci. Technol. 35 045602-045612 2. Plascencia-Cruz LE, Hernández-Rayas A, Villasenor-Mora C, Torres-Osorio J and Córdova-Fraga T 2021 Magnetic induction device for heating nanoparticles at frequencies >500 kHz J. Instrum. 16 1-13 3. Cano ME, Barrera A, Estrada JC, Hernandez A, and Cordova T 2011 An induction heater device for magnetic hyperthermia studies and specific absorption ratio measurements Rev. Sci. Instrum. 82 114904-10 4. Araújo-Neto RP, Silva-Freitas EL, Carvalho JF, Pontes TRF, Silva KL, Damasceno IHM, Egito EST, Dantas AL, Morales MA and Carriço AS 2014 Monodisperse sodium oleate Petition 870250007014, dated 01 / 28 / 2025, pp. 42 / 53 34 / 34 Magnetite-Coated High-Susceptibility Nanoparticles for Hyperthermia Applications J. Magn. Magn. Mater. 364 72-79 5. Lemine O M, Algessair S, Madkhali N, Al-Najar B and ElBoubbou K 2023 Assessing the heat generation and self-heating mechanism of superparamagnetic Fe3O4 nanoparticles for magnetic hyperthermia application: the effects of concentration, frequency, and magnetic field Nanomater 13 453-67 Petição 870250007014, de 28 / 01 / 2025, pág. 43 / 53

Claims

1 / 3 CLAIMS 1. Electronic circuit (IC) CHARACTERIZED by comprising: toroidal inductors (L1, L2); working coil (L3); resistors (R1, R2, R3, R4); zener diodes (D1, D2); rectifier diodes (D3, D4); MOSFET transistors (M1, M2) and a parallel capacitor bank (C1); wherein the parallel capacitor bank (C1) is connected in parallel to the working coil (L3); the resistors (R1, R2) are connected to a power supply and protect the rectifier diodes (D3, D4) and the transistors (M1, M2); the resistors (R3, R4) are connected to the zener diodes (D1, D2) and the zener diodes (D1, D2) are connected to the transistors (M1, M2); and the toroidal inductors (L1, L2) are configured to reduce high-frequency noise and protect the power supply.

2. Electronic circuit (IC), according to claim 1, CHARACTERIZED by comprising a parallel LC type configuration, operating with zero voltage switching (ZVS) technology.

3. Electronic circuit (IC), according to claim 1 or 2, CHARACTERIZED by being powered by a 12 V and 100 A power supply.

4. Electronic circuit (IC), according to any one of claims 1 to 3, CHARACTERIZED in that the power supply provides energy to the transistors (M1, M2), which in turn operate in a half-cycle of operation.

5. Electronic circuit (IC), according to any one of claims 1 to 4, CHARACTERIZED in that the parallel capacitor bank (C1) comprises polypropylene capacitors configured to withstand high frequency and high current, with a minimum capacitance of 200 μE; and the MOSFET transistors (M1, M2) are configured to withstand currents up to 100 A.

6. Magnetic induction device CHARACTERIZED by heating magnetic nanoparticles and comprising: an electronic circuit (IC), as defined in any one of claims 1 to 5, and integrated cooling arrangements; wherein the cooling arrangements comprise a water pump connected to a water container and connected to aluminum blocks (BA), which in turn are in contact with the transistors (M1, M2); fans (V) directed to the parallel capacitor bank (C1); and a water pump connected to a container with ice and water and connected to the working coil (L3).

7. Device according to claim 6, characterized by the fact that the fans rotate at 5000 rpm.

8. Device according to claim 6, CHARACTERIZED in that the working coil (L3) is subjected to a heat bath.

9. Device, according to claim 6, CHARACTERIZED in that the working coil (L3) is configured to generate a magnetic field with an intensity of up to 23.6 mT, as a function of an alternating current of 50 to 200 kHz supplied by the electronic circuit (IC).

10. Device according to any one of claims 6 to 9, CHARACTERIZED by operating stably for up to 100 minutes. Petition 870250007014, dated 01 / 28 / 2025, pp. 45 / 53 3 / 3 11. Device, according to any one of claims 6 to 10, CHARACTERIZED in that the device has a modular structure configured to allow the exchange of components for different configurations. Petition 870250007014, dated 01 / 28 / 2025, pp. 46 / 53

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