Design and Implementation of a Wireless Charging-Based Cardiac Monitoring System Focused on Temperature Reduction and Robust Power Transfer Efficiency

Wireless power transfer systems are increasingly used as a means of charging implantable medical devices. However, the heat or thermal radiation from the wireless power transfer system can be harmful to biological tissue. In this research, we designed and implemented a wireless power transfer system-based implantable medical device with low thermal radiation, achieving 44.5% coil-to-coil efficiency. To suppress thermal radiation from the transmitting coil during charging, we minimized the ESR value of the transmitting coil. To increase power transfer efficiency, a ferrite film was applied on the receiving part. Based on analyses, we fabricated a cardiac monitoring system with dimensions of 17 x 24 x 8 mm(3) and implanted it in a rat. We confirmed that the temperature of the wireless charging device increased by only 2 degrees C during the 70 min charging, which makes it safe enough to use as an implantable medical device charging system.11Ysciescopu

Induction of IL-10-producing CD4(+)CD25(+ )T cells in animal model of collagen-induced arthritis by oral administration of type II collagen

Induction of oral tolerance has long been considered a promising approach to the treatment of chronic autoimmune diseases, including rheumatoid arthritis (RA). Oral administration of type II collagen (CII) has been proven to improve signs and symptoms in RA patients without troublesome toxicity. To investigate the mechanism of immune suppression mediated by orally administered antigen, we examined changes in serum IgG subtypes and T-cell proliferative responses to CII, and generation of IL-10-producing CD4(+)CD25(+ )T-cell subsets in an animal model of collagen-induced arthritis (CIA). We found that joint inflammation in CIA mice peaked at 5 weeks after primary immunization with CII, which was significantly less in mice tolerized by repeated oral feeding of CII before CIA induction. Mice that had been fed with CII also exhibited increased serum IgG(1 )and decreased serum IgG(2a )as compared with nontolerized CIA animals. The T-cell proliferative response to CII was suppressed in lymph nodes of tolerized mice also. Production of IL-10 and of transforming growth factor-β from mononuclear lymphocytes was increased in the tolerized animals, and CD4(+ )T cells isolated from tolerized mice did not respond with induction of IFN-γ when stimulated in vitro with CII. We also observed greater induction of IL-10-producing CD4(+)CD25(+ )subsets among CII-stimulated splenic T cells from tolerized mice. These data suggest that when these IL-10-producing CD4(+)CD25(+ )T cells encounter CII antigen in affected joints they become activated to exert an anti-inflammatory effect

Effect of hand loads on upper extremity muscle activity during pushing and pulling motions

Manual pushing or pulling with a hand tool is a coordinated action by various upper extremity muscles. The objective of this experimental study was to examine the effects of horizontal and vertical hand loads on upper extremity muscle activity during concentric pushing and pulling exertions. Twenty young female participants conducted repetitive pushing and pulling trials with three horizontal loads (1 kg, 2 kg, 3 kg) and two vertical loads (0.6 kg, 1.3 kg) in a seated posture, while the myoelectric activity of seven upper extremity and shoulder muscles were quantified. Study results indicate that the shoulder flexor and extensor muscles were more strongly associated with horizontal load, and elbow flexors were more sensitive to vertical load. The empirical data from this systematic evaluation can offer initial insights for ergonomic design and evaluation of hand tools or occupational tasks that involve repetitive pushing or pulling

Structural insights into the elevator-like mechanism of the sodium/citrate symporter CitS

The sodium-dependent citrate transporter of Klebsiella pneumoniae (KpCitS) belongs to the 2-hydroxycarboxylate transporter (2-HCT) family and allows the cell to use citrate as sole carbon and energy source in anaerobic conditions. Here we present crystal structures of KpCitS in citrate-bound outward-facing, citrate-bound asymmetric, and citrate-free inward-facing state. The structures reveal that the KpCitS dimerization domain remains stationary throughout the transport cycle due to a hydrogen bond network as well as extensive hydrophobic interactions. In contrast, its transport domain undergoes a ~35° rigid-body rotation and a ~17 Å translocation perpendicular to the membrane to expose the substrate-binding site alternately to either side of the membrane. Furthermore, homology models of two other 2-HCT proteins based on the KpCitS structure offer structural insights into their differences in substrate specificity at a molecular level. On the basis of our results and previous biochemical data, we propose that the activity of the 2-HCT CitS involves an elevator-like movement in which the transport domain itself traverses the lipid bilayer, carrying the substrate into the cell in a sodium-dependent manner.11Nsciescopu

Methodology for Reduction of Noise Interference in Wireless Charging Implantable ECG Sensor

According to commercialization of implantable medical devices (IMDs), wireless charging system is necessary to solve the problem of battery duration. However, magnetic field generated by the wireless charging system may cause magnetic interference to the IMDs, especially, implantable ECG sensor. Therefore, this paper proposes a methodology for reduction of the noise interference at the implantable ECG sensor with wireless charging system. The methodology is to design the pattern of the trace between the sensing electrodes of the sensor using the effect of canceling the magnetic vectors. By applying the methodology, reduction of the noise interference was verified through simulation and measurement. © 2021 IEEE.11Nscopu

Methodology for Reduction of Noise Interference in Wireless Charging Implantable ECG Sensor

According to commercialization of implantable medical devices (IMDs), wireless charging system is necessary to solve the problem of battery duration. However, magnetic field generated by the wireless charging system may cause magnetic interference to the IMDs, especially, implantable ECG sensor. Therefore, this paper proposes a methodology for reduction of the noise interference at the implantable ECG sensor with wireless charging system. The methodology is to design the pattern of the trace between the sensing electrodes of the sensor using the effect of canceling the magnetic vectors. By applying the methodology, reduction of the noise interference was verified through simulation and measurement. © 2021 IEEE.1

Wireless Torque and Power Transfer Using Multiple Coils with LCC-S Topology for Implantable Medical Drug Pump

In this paper, we propose a method of wirelessly torque transfer (WTT) and power (WPT) to a drug pump, one of implantable medical devices. By using the magnetic field generated by the WPT system to transfer torque and power to the receiving coil at the same time, applications that previously used power from the battery can be operated without a battery. The proposed method uses a receiving coil with magnetic material as a motor, and can generate torque in a desired direction using the magnetic field from the transmitting coil. The WPT system was analyzed using a topology that generates a constant current for stable torque generation. In addition, a method for detecting the position of the receiving coil without using additional power was proposed. Through simulations and experiments, it was confirmed that WTT and WPT were possible at the same time, and in particular, it was confirmed that WTT was stably possible

Improved Calculation Method of Coupling Factors for Low-Frequency Wireless Power Transfer Systems

The concept of a coupling factor was introduced in International Electrotechnical Commission (IEC) 62311 and 62233 to provide a product safety assessment that considers the localized exposure when an electromagnetic field (EMF) source is close to the human body. To calculate the coupling factors between the human body and EMF source, a numerical calculation should be carried out to calculate the internal quantities of the human body models. However, at frequencies below 10 MHz, the computed current density or internal electric field has computational artifacts from segmentation or discretization errors. Specifically, coupling factors are calculated based on the maximum values, which may include computational artifacts due to abnormal peaks. In this study, we propose an improved calculation method to remove computational artifacts by applying the 99.99th percentile in calculating the coupling factors without underestimation. The performance of the proposed method is verified through a comparison based on various human body models with wireless power transfer (WPT) systems and compliance with the reference levels and basic restrictions. The results indicate that the proposed method can provide uniform coupling factors by reducing the computational errors by up to 65.3% compared to a conventional method

Design Considerations for Adding Series Inductors to Reduce Electromagnetic Field Interference in an Over-Coupled WPT System

This paper analyzes how over-coupled coils affect odd harmonic current and electromagnetic interference (EMI) in a wireless power transfer (WPT) system, and proposes design considerations for series inductors to solve the EMI problem. When the air gap of the coils of the WPT system decreases below a certain level and the coils are over-coupled, the odd harmonic component of the input impedance of the system decreases and odd harmonic currents increase. The increase in the odd harmonic components current quickly aggravates the EMI issues. To solve the EMI problem of the over-coupled WPT system, additional series inductors were applied to the system, and considerations for designing the series inductors were analyzed. When designing additional series inductors, power transfer efficiency, maximum power transfer, input impedance and odd harmonic components current must be considered. Using simulations and experiments, it was confirmed that the WPT system designed with analyzed considerations maintained relatively high efficiency and reduced EMI issues

The Magnetic Energy Harvester With Improved Power Density Using Saturable Magnetizing Inductance Model for Maintenance Applications Near High Voltage Power Line

Recently, maintenance applications around power lines have been actively studied. These applications usually supply power through magnetic energy harvesting(MEH) to devices around the power line. A major challenge for practical MEH is to overcome magnetic saturation, which can cause degradation of power density under a wide current range in the power line. In this paper, we propose a design methodology to harvest maximized output power by considering the saturation effect. To consider magnetic saturation, the output power model and the saturable magnetizing inductance model based on magnetizing current were comprehensively analyzed. Additionally, the critical point of saturation for the maximum harvested power was analyzed by considering different primary side current conditions. With the proposed design methodology, the accuracy and efficiency of the output model were verified with experimental results compared to the conventional model. To consider the real environment, a 150 kW class of AC resistor load bank was implemented to control the primary current from 0 to 100 A with power frequency of 60 Hz. Experimental results show that the proposed method can harvest an average power of 14.32 W on 70 A power line, which is an increase of 39.8 % compared with the conventional design method