Wireless Power Transfer Devices Research Articles

Contact Lens that Enabled Early Diagnosis for Diseases Induced by Oxidative Stress and Potassium Ion (K+) in Ocular Tissues

The present study used sensor technology to design a lens that could replace a docto.r It consists of an oxidative stress sensor, a (K+) ion sensor and a pressure sensor placed on a Lotrafilcon A silicone hydrogel lens for early diagnosis, as well as a recording and display device that the user can use on their own, recording 24 hours a day and alerting when needed. Additionally, power will be provided to the sensors for data transmission via an external wireless power transfer device. The oxidative stress sensor detects oxidative stress in the structures of the eye and indicates that the patient may have an abnormal condition like diabetic retinopathy, glaucoma and cataracts. Likewise, the (K +) ion sensor detects the (K +) ion concentration in the ocular cells and detects abnormal conditions where the concentration is elevated. The pressure sensor allows the intraocular pressure of patients diagnosed with glaucoma to be kept under control. This way, diseases can be diagnosed early, and continuous monitoring and control of the disease will be ensured. This will prevent the user from having to make frequent visits to the hospital, while also reducing the workload.

Experimental Results and Analysis of Midrange Underwater Asymmetric Wireless Power Transfer

The eddy current loss caused by the conductivity of seawater results in a relatively low transfer efficiency of underwater wireless power transfer (WPT). And the transfer distance of the current WPT system is relatively short. Considering that most of the wireless power transfer devices in practical applications are asymmetric, few studies have explored the transfer characteristics of asymmetric midrange WPT in seawater. In this study, it is experimentally found that the load voltage and transfer efficiency of an asymmetric midrange WPT system with reduced primary balancing resistance in seawater are nearly twice as high as those of a symmetric one at a 50 cm transfer distance and a 410 kHz operation frequency with a 44.4 Ω load resistance. A new circuit model of the underwater WPT system with complex impedance and complex mutual inductance is then presented, and the load voltages predicted by the model are consistent highly with the experimental values; the model is then utilized for the explanation of the experimental observations. Changing the load resistance also improves the transfer efficiency of the system; however, the eddy current loss results in a relatively low transfer efficiency of 30.9% at an optimal load resistance of 90 Ω. The asymmetric midrange underwater WPT system can be applied in scenarios where the transfer distance is prioritized.

Comparison of pulsed and continuous electromagnetic field generated by WPT system on human dermal and neural cells

In recent decades, we have seen significant technical progress in the modern world, leading to the widespread use of telecommunications systems, electrical appliances, and wireless technologies. These devices generate electromagnetic radiation (EMR) and electromagnetic fields (EMF) most often in the extremely low frequency or radio-frequency range. Therefore, they were included in the group of environmental risk factors that affect the human body and health on a daily basis. In this study, we tested the effect of exposure EMF generated by a new prototype wireless charging system on four human cell lines (normal cell lines—HDFa, NHA; tumor cell lines—SH-SY5Y, T98G). We tested different operating parameters of the wireless power transfer (WPT) device (87–207 kHz, 1.01–1.05 kW, 1.3–1.7 mT) at different exposure times (pulsed 6 × 10 min; continuous 1 × 60 min). We observed the effect of EMF on cell morphology and cytoskeletal changes, cell viability and mitotic activity, cytotoxicity, genotoxicity, and oxidative stress. The results of our study did not show any negative effect of the generated EMF on either normal cells or tumor cell lines. However, in order to be able to estimate the risk, further population and epidemiological studies are needed, which would reveal the clinical consequences of EMF impact.

Parameter and Topology Optimizations for Wireless Power Transfer Device Considering Magnetic and Circuit Properties

Parameter and Topology Optimizations for Wireless Power Transfer Device Considering Magnetic and Circuit Properties

Design and simulation of a rectangular planar printed circuit board coil for nuclear magnetic resonance, radio frequency energy harvesting, and wireless power transfer devices

AbstractIn this study, a planar printed circuit board (PCB) coil with FR4 substrate was designed and simulated using the finite element method, and the results were analyzed in the frequency domain. This coil can be used in wireless power transfer (WPT) as a transmitter or receiver, eliminating wires. It can also be used as the receiver in radio frequency energy‐harvesting (RF‐EH) systems by optimizing the planar PCB coil to convert radio‐wave energy into electricity, and it can be employed as an excitation (transmitter) or receiver coil in nuclear magnetic resonance (NMR) spectroscopy. This PCB coil can replace the conventional coil, yielding a reduced occupied volume, a fine‐tuned design, reduced weight, and increased efficiency. Based on the calculated gain, power, and electromagnetic and electric field results, this planar PCB coil can be implemented in WPT, NMR spectroscopy, and RF‐EH devices with minor changes. In applications such as NMR spectroscopy, it can be used as a transceiver planar PCB coil. In this design, at frequencies of 915 MHz and 40 MHz with 5 mm between coils, we received powers of 287.3 W and 480 W, respectively, which are suitable for an NMR coil or RF‐EH system.

Evaluation of Electromagnetic Exposure of the Human with a Coronary Stent Implant from an Electric Vehicle Wireless Power Transfer Device

The aim of this paper is to analyze in depth the coupling between leakage electromagnetic fields (EMFs) generated by an electric vehicle wireless power transfer (EV-WPT) device under misaligned operating conditions and metallic coronary stents, which could be potentially hazardous to human electromagnetic safety. In this paper, we established that a standing human with a coronary stent implant and a sitting human with a coronary stent implant are exposed to the leaked EMFs of an EV-WPT device with a transmission power of 11 kW and 22 kW and a transmission frequency of 85 kHz, and we quantified the induced E-field strength of the human body by considering the x- and z-axis misalignment ranges of the WPT device as [−75 mm, 75 mm]. The results showed that the enhancement of the induced E-field in the human tissues near the sharp edges of the implant is significant. Meanwhile, the larger the WPT device misalignment generated, the higher the transmission power, and the closer the human body is to the WPT device, the larger the induced E-fieldmax value of the human body is, which has the possibility of exceeding the ICNIRP safety limit, and there is a potential human body electromagnetic safety problem.

A Multi-Domain Model for Variable Gap Iron-Cored Wireless Power Transmission System

Wireless power transfer (WPT) devices represent one of the most efficient and increasingly used technologies for the transfer of data and power in the near-field range. This work analyzes and describes a new type of device: a ferrite-cored, variable gap, high-frequency power and data transfer system. The classic theoretical models existing in the literature for near-field communication (NFC) and WPT devices have foreseen a lumped-parameters characterization based on the representation of an equivalent circuit model (ECM). The strict interdependence between the different physical domains has clearly increased the difficulty in predicting the behavior of the device, due to the unwanted continuous and chaotic variation of the parameters. The proposed paper aims to provide a general and reliable multi-physics model based on the co-simulation of a Spice®-based ECM analysis and the ESRF Radia®-based 3D finite volume methodology (3DFVM), placing particular emphasis on the intrinsic sensitivity with respect to variables that cannot be directly controlled, such as the variation of the air gap between the coupled coils interfaces. Furthermore, this work outlines a detailed and effective experimental methodology for the estimation of static and dynamic electro-magnetic parameters and the validation of the numerical models in both the time and frequency domain, through the analysis of a real coupled WPT device.

Cylindrical Transmitting Coil for Two-Dimensional Omnidirectional Wireless Power Transfer

Megahertz-range wireless power transfer has become a promising approach for increasing spatial freedom of charging. This article proposes a cylindrical-shaped coil, which can produce the homogeneous magnetic field in a plane. The coil consists of two helical windings, which are wound to guide the current in opposite directions. A single power source is used to excite the transmitter without any current amplitude or phase control circuits. Furthermore, since the parasitic capacitance of the coil is not negligible due to the complexity of the coil shape, we develop a general equivalent model with parasitic capacitance for the analysis of complex coils. The system efficiency of the proposed omnidirectional wireless power transfer device is validated by a practical experiment. The measured dc-to-dc efficiency of approximately 72.4% and the load power of 13 W are demonstrated for the proposed wireless charging system at 6.78-MHz operating frequency. Finally, we verify that the electromagnetic exposure satisfies the safety regulations.

An ultrasound-induced wireless power supply based on AlN piezoelectric micromachined ultrasonic transducers

Wireless power transfer is one of the enabling technologies for powering implantable biomedical devices. Biocompatibility and CMOS compatibility of wireless power transfer devices are highly desired due to safety and footprint concerns. Toward implantable applications, this paper presents an ultrasound-induced wireless power supply based on AlN piezoelectric micromachined ultrasonic transducer (PMUT). The wireless power supply integrates wireless power transfer, power management and energy storage functions. The PMUT array is used as a passive wireless power receiver, followed by electrical impedance matching networks and a voltage multiplier for efficient power transmission and rectification. The output power intensity of the wireless receiver reaches 7.36 μW/mm2 with an incident ultrasound power below the FDA safety limit. The output power of the wireless power supply reaches 18.8 μW and a 100-μF capacitor is fully charged to 3.19 V after power management, which are sufficient to power many low-power implantable biomedical devices such as for neural electrical stimulation, biosensors and intrabody communication applications. The wireless power supply is implemented in a PCB with a diameter of 1 cm. With biocompatibility and CMOS compatibility of AlN thin film compared to commonly used PZT, the proposed solution paves the way for safer and ultraminiaturized wireless power supplies with further development incorporating all the functions on a monolithic chip in the future.

Near-Field Wireless Power Transfer for 6G Internet of Everything Mobile Networks: Opportunities and Challenges

Radiating wireless power transfer (WPT) brings forth the possibility to cost-efficiently charge wireless devices without requiring a wiring infrastructure. As such, it is expected to play a key role in the deployment of limited-battery communicating devices, as part of the 6G-enabled Internet of Everything (IoE) vision. To date, radiating WPT technologies are mainly studied and designed assuming that the devices are located in the far-field region of the power radiating antenna, resulting in relatively low energy transfer efficiency. However, with the transition of 6G systems to mmWave frequencies combined with the use of large-scale antennas, future WPT devices are likely to operate in the radiating near-field (Fresnel) region. In this article, we provide an overview of the opportunities and challenges that arise from radiating near-field WPT. In particular, we discuss the possibility to realize beam focusing in near-field radiating conditions, and highlight its possible implications for WPT in future IoE networks. Furthermore, we overview some of the design challenges and research directions that arise from this emerging paradigm, including its simultaneous operation with wireless communications, radiating waveform considerations, hardware aspects, and operation with typical antenna architectures.

Machine Learning Assisted Characteristics Prediction for Wireless Power Transfer Systems

One of the main challenges in wireless power transfer (WPT) devices is performance degradation when the receiver’s position and characteristics vary. Therefore, the load resistance and receiver position must be monitored to ensure proper optimization of power transfer. This study proposes a machine learning (ML) assisted method that estimates the power delivered to the receiver by only using measurements at the transmitter side. Based on the delivered power estimation, we also propose a method to identify if the system efficiency is too low, so that the transmitter should be turned off. This activation control method can be useful in multi-transmitter WPT systems. In addition, we propose an ML method to estimate the load resistance and the coupling coefficient. Using the proposed method, the characteristics of an inductor-capacitor-capacitor (LCC)-Series tuned WPT system are successfully predicted only using the measured root-mean-square and the harmonic contents of the input current. The proposed approach is experimentally validated using a laboratory prototype.

Wireless Power Transfer Device Based on RF Energy Circuit and Transformer Coupling Procedure

It is possible to transmit electricity wirelessly without the need for cables. Wireless power transmission makes it possible to link remote places that would otherwise be cut off from access to reliable electricity. A wireless connection to the power supply is expected in the future. This study describes the experimental results of Wireless Power Transfer (WPT) utilizing a transformer coupling approach and its future potential. This WPT device (WPTD) is used to transmit power using two procedures of energy transfer: radiofrequency coupling and transformer coupling, both of which are magnetic based, in principle. The distance between the transmitter and receiver of the system affects the amount of power that can be sent. Research is performed to establish how far apart the system's transmitter and receiver should be. Magnetic fields may transmit energy between two coils, but the distance between the two coils must be too close for this approach to work. Aside from that, it assesses the setting parameter of a value that has been tabulated using a certain application, in the findings and discussion parts.

Topology optimization of magnetic cores for WPT using the geometry projection method

PurposeThe purpose of this study is to search for an optimal core shape that is robust against misalignment between the transmitting and receiving coils of the wireless power transfer (WPT) device. During the optimization process, the authors maximize the coupling coefficients while minimizing the leakage flux around the coils to ensure the safety of the WPT device.Design/methodology/approachIn this study, a novel topology optimization method for WPT devices using the geometry projection method is proposed to optimize the magnetic core shape. This method facilitates the generation of bar-shaped magnetic cores because the material distribution is represented by a set of elementary bars.FindingsIt is shown that an optimized core shape, which is obtained through topology optimization, effectively increases the net magnetic flux interlinked with the receiving coil and outperforms the conventional core.Originality/valueIn the previous topology optimization method, the material distribution is represented by a linear combination of Gaussian functions. However, this method does not usually result in bar-shaped cores, which are widely used in WPT. In this study, the authors propose a novel topology optimization method for WPT devices using geometry projection that is used in structural optimization, such as beam and cantilever shapes.

Analysis of the Transformer Characteristics for an Integration System with a Wireless Power Transfer Device and Linear Motor

This paper proposed the transformer characteristic analysis method for the wireless power transfer (WPT) device and linear motor (LM) integration system that can be applied to industrial cleanroom transfer systems. A cable is required to supply the power in conventional systems. In comparison, the proposed system utilizes a WPT device that can simplify power transfers and make a better space utilization. The shape of the wireless power transmission system is proposed along with the discussion of the 2D FEA analysis method about the inductance analyzing method, which are important parameters in magnetic coupling. In addition, ferrite iron loss was calculated based on the analysis results, and applied to the entire modeling circuit to verify the validity of the measured and analyzed values. Finally, the proposed analysis method for the transformer coupling characteristics of the wireless power transfer combined with the transfer system is verified by experiments and simulations.

Rational Design of Electrochemiluminescent Devices.

Electrochemiluminescence (ECL) is a light-emitting process which combines the intriguing merits of both electrochemical and chemiluminescent methods. It is an extensively used method especially in clinical analysis and biological research due to its high sensitivity, wide dynamic range, and good reliability. ECL devices are critical for the development and applications of ECL. Much effort has been expended to improve the sensitivity, portability, affordability, and throughput of new ECL devices, which allow ECL to adapt broad usage scenarios.In this Account, we summarize our efforts on the recent development of ECL devices including new electrodes, ECL devices based on a wireless power transfer (WPT) technique, and novel bipolar electrochemistry. As the essential components in the ECL devices, electrodes play an important role in ECL detection. We have significantly improved the sensitivity of luminol ECL detection of H2O2 by using a stainless steel electrode. By using semiconductor materials (e.g., silicon and BiVO4), we have exploited photoinduced ECL to generate intense emission at much lower potentials upon illumination. For convenience, portability, and disposability, ECL devices based on cheap WPT devices have been designed. A small diode has been employed to rectify alternating current into direct current to dramatically enhance ECL intensity, enabling sensitive ECL detection using a smart phone as a detector. Finally, we have developed several ECL devices based on bipolar electrochemistry in view of the convenience of multiplex ECL sensing using a bipolar electrode (BPE). On the basis of the wireless feature of BPE, we have employed movable BPEs (e.g., BPE swimmers and magnetic rotating BPE) for deep exploration of the motional and ECL properties of dynamic BPE systems. To make full use of the ECL solution, we have dispersed numerous micro-/nano-BPEs in solution to produce intense 3D ECL in the entire solution, instead of 2D ECL in conventional ECL devices. In addition, the interference of ECL noise from driving electrodes was minimized by introducing the stainless steel with a passivation layer as the driving electrode. To eliminate the need for the fabrication of electrode arrays and the interference from the driving electrode and to decrease the applied voltage, we develop a new-type BPE device consisting of a single-electrode electrochemical system (SEES) based on a resistance-induced potential difference. The SEES is fabricated easily by attaching a multiperforated plate to a single film electrode. It enables the simultaneous detection of many samples and analytes using only a single film electrode (e.g., screen-printed electrode) instead of electrode arrays. It is of great potential in clinical analysis especially for multiple-biomarker detection, drug screening, and biological studies. Looking forward, we believe that more ECL devices and related ECL materials and detection methods will be developed for a wide range of applications, such as in vitro diagnosis, point-of-care testing, high-throughput analysis, drug screening, biological study, and mechanism investigation.

Prospective Powering Strategy Development for Intelligent-Tire Sensor Power Charger Application

Tire sensors embedded in a vehicle tire are stand-alone autonomous devices. A tire sensor reserve power strategy is crucial due to sensor energy sources limitations for long operational periods. This paper presents an innovative tire sensor powering strategy for the intelligent-tire system. The powering strategy offers a green concept, maintenance-free, and low-cost method in order to extend the tire sensor lifetime for long operating periods. The proposed strategy adopts wireless power transfer (WPT) technology to transfer power to an electrical load mounted on the rotational system without an interconnection cable. It is composed of a power transmitter designed to be mounted on the vehicle’s inner fender liner, and a power receiver that provides power to recharge the tire sensor battery/energy storage. The transmitter transfers power from the vehicle battery/accumulator to a power receiver coupled with the tire sensor which is mounted on the vehicle tire inner wall. WPT devices were designed based on induction electromagnetic coupling and can provide an output current up to 1A at 5 V. The proposed powering strategy was verified using a vehicle tire simulator model to emulate rotational motion. A voltage and current sensor module as well microcontroller and data logger modules were utilized as the load for the developed WPT system. The verification experimental and preliminary test results reveal that the proposed strategy can provide constant power to the load (in this case, the voltage is around 4.3 V and the current is around 21.1 mA) although the vehicle tire model was rotated at different speeds from 0 rpm to 800 rpm. The proposed system has the potential and feasibility for implementation in tire sensor power applications in the intelligent-tire system.

An Application of a Wireless Power Transfer at Low Frequency Range

In this study, a low frequency wireless power transfer (LFWPT) device has been designed and implemented. The aim of investigation of low frequency system is to eliminate the un-healthy situation due to non-ionized radiation of the high frequency regimes. The transmitter uses a special winding to transmit the electromagnetic signals to the environment, especially for a few centimeters distance. The receiver winding, which is the same with the transmitter winding catches the signal and stores it in capacitor. The system uses maximum 17,649 Hz to transmit the signal, that is fairly low compared to the other studies in the literature. A DC-AC inverter is used to obtain high frequency signals for the transmitter circuit. The experiments have proven that the receiving antenna can get 1 V amplitude from the transmitted peak-to-peak amplitude of 140 V at the operation frequency.

Actively controlled asymmetric edge states for directional wireless power transfer.

Wireless power transfer (WPT) has triggered immense research interest in a range of practical applications, including mobile phones, logistic robots, medical-implanted devices and electric vehicles. With the development of WPT devices, efficient long-range and robust WPT is highly desirable but also challenging. In addition, it is also very important to actively control the transmission direction of long-range WPT. Recently, the rise of topological photonics provides a powerful tool for near-field robust control of WPT. Considering the technical requirements of robustness, long-range and directionality, in this work we design and fabricate a one-dimensional quasiperiodic Harper chain and realize the robust directional WPT using asymmetric topological edge states. Specially, by further introducing a power source into the system, we selectively light up two Chinese characters, which are composed of LED lamps at both ends of the chain, to intuitively show the long-range directional WPT. Moreover, by adding variable capacitance diodes into the topological quasiperiodic chain, we present an experimental demonstration of the actively controlled directional WPT based on electrically controllable coil resonators. With the increase in voltage, we measure the transmission at two ends of the chain and observe the change of transmission direction. The realization of an actively tuned topological edge states in the topological quasiperiodic chain will open up a new avenue in the dynamical control of robust long-range WPT.

Precise Modeling of Mutual Inductance for Planar Spiral Coils in Wireless Power Transfer and Its Application

In magnetic coupling resonant wireless power transfer devices, planar spiral coils are often used as the coupling mechanism. In such application area, the coils are often wound sparsely with wide screw pitches and often under complex relative position. An accurate model of mutual inductance for planar spiral coils wound either densely or sparsely is established in this article. Utilizing Euler Angles, an exact expression of mutual inductance for a couple of planar spiral coils under arbitrary relative position is proposed. Based on this expression and geometric mean distance principle, a self-inductance expression for planar spiral coils is derived. Based on numerical calculation of the expressions proposed in this article, the influence of precession and spin angle on mutual inductance is studied; the method of determining radius of each turn when using traditional concentric circular filaments cluster approximation model for self- and mutual inductance calculation is studied; the difference of calculation results between the accurate model and the traditional approximation model is compared. Finite element simulation and experimental results verify the correctness of the proposed models.

Design of Wireless Power and Information Transfer Systems Considering Figure of Merit for Information

Inductively coupled resonant wireless power transfer (WPT) systems can be used as a wireless power and information transfer (WPIT) system by properly adding the function of varying Rx loads. A new metric for the figure of merit for information transfer from Rx to Tx is proposed as the ratio of Tx input impedances for the Rx shorted and optimum loads to systematically assess the information transfer. While most of WPT and near-field communication (NFC) devices have been adopted for very short distances between Tx and Rx, this work shows that the WPIT systems using inductively coupled resonant structures with high Q-factor coils enable much longer working distances with the best power transfer efficiency and information transfer capability. Several design examples show that the newly proposed figure of merit for information transfer is an essential metric in the understanding and design of WPIT systems. The theory is validated with circuit and electromagnetic simulations for various system configurations.