Temporary cardiac pacemakers used in periods of need during surgical recovery involve percutaneous leads and externalized hardware that carry risks of infection, constrain patient mobility and may damage the heart during lead removal. Here we report a leadless, battery-free, fully implantable cardiac pacemaker for postoperative control of cardiac rate and rhythm that undergoes complete dissolution and clearance by natural biological processes after a defined operating timeframe. We show that these devices provide effective pacing of hearts of various sizes in mouse, rat, rabbit, canine and human cardiac models, with tailored geometries and operation timescales, powered by wireless energy transfer. This approach overcomes key disadvantages of traditional temporary pacing devices and may serve as the basis for the next generation of postoperative temporary pacing technology. A biodegradable pacemaker without external leads improves the safety of temporary cardiac pacing.

Fully implantable and bioresorbable cardiac pacemakers without leads or batteries.

In this paper, we present the design of cylindrical and spherical electromagnetic cloaks working at visible frequencies. The cloak design is based on the employment of layered structures consisting of alternating plasmonic and non-plasmonic materials and exhibiting the collective behavior of an effective epsilon-near-zero material at optical frequencies. The design of a cylindrical cloak to hide cylindrical objects is firstly presented. Two alternative layouts are proposed and both magnetic and non-magnetic objects are considered. Then, the design of spherical cloaks is also presented. The full-wave simulations presented throughout the paper confirm the validity of the proposed setup, and show how this technique can be used to reduce the observability of cylindrical and spherical objects. The effect of the losses is also considered.

Plasmonic metamaterial cloaking at optical frequencies

With the growing adoption of electric vehicles (EVs), there is a pressing need for constructing charging infrastructures. In this context, wireless charging technology has been under development for the past few decades. Dispensed with awkward plugs and wires, wireless power transfer (WPT) technology is very safe, convenient and easy-to-use. Researchers have taken sustained efforts to make it an improved technology and automakers also work to provide the wireless charging option for their customers. In this paper, the basic principles of resonant inductive power transfer that is common-used for wireless electric vehicle charging (WEVC) are elaborated. Then, with a different emphasis on WEVC technologies, the key issues in academia and industry are discussed respectively. The core technologies of a fully-function WEVC system in academia are summarized and a comparative study is conducted among the selected WEVC industry standards. In addition, based on the possible technical development and currently valid policies, the author envisions the future of WEVC, followed by some conclusions and helpful advice.

The state-of-the-arts of wireless electric vehicle charging via magnetic resonance: principles, standards and core technologies

With the recent advancement and progress in the field of wireless power transfer (WPT), there is an ever increasing demand for high power transfer efficiency (PTE) of the WPT systems and improved transfer distance for the end-users. However, some existing WPT systems have limited PTE and transfer distance as they take the inductive coupling approach, where the PTE dramatically decreases as the distance between (Tx) and receiver (Rx) coils increases. Alternatively, magnetic resonance coupling (MRC) is used as a mid-range WPT approach, for which the insertion of metamaterials (MTMs) between Tx and Rx coils is exploited to improve efficiency. MTMs are artificially engineered materials that show uncommon electromagnetic properties, such as evanescent wave amplification and negative refractive characteristics, which could be utilized for the enhancement of PTE. In this article, a comprehensive review on recent progresses in the MTM-based WPT systems is reported, where previously reported MTM-based WPT systems are compared in terms of various parameters such as configurations, operating frequencies, dimensions and PTE. Also, the PTEs of these systems were plotted as a function of the normalized transfer distance. This review is expected to provide an insight for understanding the trends of the MTM-based WPT systems and serve as a reference for researchers who work on WPT systems and their applications.

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Wireless Power Transfer Systems Using Metamaterials: A Review

As we enter the new year of 2019, at the time of this writing, we are glad to report that our journal, IEEE Journal of Emerging and Selected Topics in Power Electronics (IEEE JESTPE) now stands among the top 3% of all journals in electrical and electronic engineering. The metrics that IEEE reported for the year of 2017 are: Impact factor of 5.117, Eigen Factor of 0.00996, and Article Influence Score of 1.892. For JESTPE to achieve such great influence in its short five-year history, from its inception in 2013 to 2017, is quite an accomplishment. As the founding Editor-in-Chief, I am extremely thankful for the good fortune that I have had to work with the large number of talented volunteers on our regular editorial board and guest editorial board.

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Editorial IEEE Journal of Emerging and Selected Topics in Power Electronics

In order to meet both safety and efficiency requirements of wireless power transfer (WPT) systems, reducing electromagnetic field (EMF) leakage and improving efficiency are critical factors in the implementation of systems. Recently, metamaterials have exhibited the ability to control the electromagnetic wave propagation. In this paper, the WPT system integrating with near-field mu-near-zero (NF-MNZ) and mu-negative permeability (MNG) metamaterials is proposed to control EMF leakage below a certain level and improve transfer efficiency. The NF-MNZ and the MNG metamaterials are placed on both sides and in the middle of the WPT system, respectively. In addition, the property of the NF-MNZ metamaterial slab and its working principle on the WPT system are analyzed. The shielding performance of the NF-MNZ metamaterial are evaluated via numerical simulation and experimental investigation. Finally, the efficiency and the magnetic field strength of the WPT system with two different types of metamaterials have been investigated by the experimental measurements. At the transfer distance of 40 cm, the experimental results show that the efficiency of the WPT system is increased by 12.06% and the magnetic field strength is reduced by 62.09%.

Investigation of Negative and Near-Zero Permeability Metamaterials for Increased Efficiency and Reduced Electromagnetic Field Leakage in a Wireless Power Transfer System

The wireless power transfer (WPT) has attracted considerable attention due to its convenience and reliability. However, the electromagnetic leakage of WPT can be harmful to humans and environment. In order to meet safety requirements, electromagnetic leakage to the nearby transmission channel should be controlled below a certain level. Beyond ferrite and metallic shields, several researchers have proposed mu-near-zero metamaterial (MNZ MM). However, little work researches the application of MNZ MM in four-coil WPT systems. Here, the authors propose an optimised MNZ MM for shielding leaked electromagnetic field. Next, the authors setup a miniaturised WPT system loaded with MNZ slab at 13.56 MHz. It can serve as a frequency selector that reflected a specified frequency of 13.56 MHz, while allowing all other frequencies to pass undisturbed. As a result, the transmission efficiency is dramatically reduced at a 30 cm distance. The magnetic field magnitude of the receiver has been decreased. Obviously, the proposed MNZ MM has good performance in magnetic field shielding for WPT systems.

Shielding the magnetic field of wireless power transfer system using zero-permeability metamaterial

A contactless energy charging platform is an emerging technology that can improve the conveniences of electronic charging devices. This article presents a novel asymmetric wireless power transfer (WPT) system by integrating with two kinds of dual-band metamaterials, which is suitable for recharging the portable electronic devices. The design key of the metamaterial is to achieve the dual-band negative permeability (DB-MNG) and near-zero permeability (DB-MNZ) for enhancing efficiency and reducing leakage magnetic field of the WPT system, simultaneously. Especially, the corresponding simulation and experimentation are carried out to verify the validity of the DB-MNG metamaterial for increasing the efficiency at 13.56 and 27.12 MHz. Moreover, considering the charging environment of portable devices, various misalignments between the device and DB-MNG metamaterial are discussed to maintain continuous power availability. Meanwhile, the dual-band shielding performance of DB-MNZ metamaterial is proved at 13.56 and 27.12 MHz. As a result, the DB-MNZ metamaterial shield performs better than ferrite sheet and its performance is similar to that of aluminum sheet.

A Dual-Band Negative Permeability and Near-Zero Permeability Metamaterials for Wireless Power Transfer System

The wireless power transfer system (WPT) is becoming increasingly important for smart home automation, in which an array of wireless sensors is used to monitor and manage smart devices and furniture. Charging the sensors, which may require different frequencies, at any position in the home is a challenge. In this article, a dual-band omnidirectional 3-D WPT system is introduced for the sensors in a smart home. The power transmitted by the transmitter can be received by any receivers operating at 13.56 and 27.12 MHz located at any position. The dual-band 3-D square and circular transmitters are designed and demonstrated. In particular, an equivalent circuit model of the proposed system is derived and numerically analyzed. In addition, the efficiency of the dual-band 3-D WPT system is evaluated based on the receiving angle through simulation and measurement. At a 16 cm distance, the system can achieve efficiencies of 61.6% and 65.4% (57.15% and 61.2%) for rotating 360° at 13.56 and 27.12 MHz without a null value in the square (circular) system. Furthermore, the effect of the angular misalignment of the receiver on efficiency is also analyzed. Finally, the performance of the WPT system in a concrete structure is validated for practical scenarios.

Design and Analysis of an Omnidirectional Dual-Band Wireless Power Transfer System

In this paper, a mid-range wireless power transfer (WPT) system based on metamaterials (MMs) has been presented. It has been shown that the MMs are positioned in the WPT system to focalize the electromagnetic field for distance enhancement and efficiency improvement theoretically and experimentally. The MMs were fabricated by using a single layer printed-circuit board (PCB) with the negative magnetic permeability, μr. An applicable impedancetuning technology was implemented by changing the operating distance between the drive (load) resonator and the internal resonator, which can achieve the optimal load of the system. In addition, the Class-E RF (radio frequency) power amplifier is firstly proposed as the high frequency excitation source of the WPT system based on the MMs due to its simple design and high efficiency. The proposed technology can achieve efficiency improvements of 4.26% and 9.13% at distances of 100 cm and 200 cm around the 2.80 MHz WPT system with the MMs, respectively. Specially, it is worth mentioning that the system efficiency is enhanced by 18.58% at 160 cm. The measured results indicate the WPT system based on the MMs can assure a stable output power of 5W at a transfer distance of 200 cm.

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Xiong Tao

Papers

Investigation of Negative and Near-Zero Permeability Metamaterials for Increased Efficiency and Reduced Electromagnetic Field Leakage in a Wireless Power Transfer System

Shielding the magnetic field of wireless power transfer system using zero-permeability metamaterial

A Dual-Band Negative Permeability and Near-Zero Permeability Metamaterials for Wireless Power Transfer System

Design and Analysis of an Omnidirectional Dual-Band Wireless Power Transfer System

Analysis and Optimized Design of Metamaterials for Mid-Range Wireless Power Transfer Using a Class-E RF Power Amplifier