From materials to systems: resonant inductive coupling for wireless bioelectronics

Recent research in wireless power transfer (WPT) using resonant inductive coupling has demonstrated very high efficiencies at large distances compared to the transmitting element dimensions, thereby increasing the number of potential applications of WPT. Since resonant inductive coupling is a very multidisciplinary field of research, different approaches have been proposed to predict the behaviour of these systems from the physical theory of resonators (coupled-mode theory) and circuit theory. Although the equivalence of these models for a point-to-point link has already been studied together with the performance metrics Power Transferred to the Load (PTL) and Power Transfer Efficiency (PTE), the new challenges and applications of this technology emphasize the necessity of analytical models to predict and assess the behavior of Multiple Input - Multiple Output (MIMO) links. In this article we revisit the current analytical models from the MIMO perspective, derive the analytical equations for the equivalent performance metrics PTE and PTL and demonstrate how to maximize them in a non-radiative resonant wireless power transfer link from a circuit-centric point of view, providing design guidelines in terms of optimal source and load impedances. This work concludes with a prospective discussion on open challenges of WPT. © 2014 IEEE.

Minirobots which are under the field of miniature robotics, have a dimension of a few centimetres to even a few millimetres. Conventionally, these small sized robots are usually powered up by batteries. The batteries can take up a lot of space and result in a bulky system. Isolating the energy storage components from the robot itself can provide a good alternative to further down sized the robot. This can be done with the incorporation of wireless power transfer (WPT) technology. However, studies of small-size WPT are usually reported with poor efficiency. The objective of this paper is to present an efficient wireless power transfer framework for the minirobot by employing the resonant inductive coupling together with impedance matching technique. The theory and design process will be discussed. Then, a simple prototyping experiment was conducted to verify the proposed framework. Result showed 35% transfer efficiency had been achieved on a transmission distance of 0.5 cm. The proposed framework had also successfully powered a 4 watts minirobot prototype at about 16% transfer efficiency where its receiver coil was located 3.5 cm above the transmitter coil.

This study presents a high efficiency inductive power link aiming for the implanted biomedical devices. Improving the efficiency of the inductive link is critical, since the overall efficiency of a remote powering system is dominated by the inductive link. Therefore, the proposed system utilizes the resonance phenomenon which enables maximum energy transfer between objects which are at resonance. In this study, the resonance is created between 4 spiral coils which are implemented on the internal and external units; each formed by two concentric coils. The system operates with 72% power efficiency at 10-12 MHz band at 10 mm distance which is a reasonable distance for powering implanted devices. Moreover, the characterization of the resonant inductive link with respect to distance and frequency is performed.

In this modern era, electricity has become the life’s heart.Even a moment without electricity makes you thinking as though you go dry. The major source of transmission of conventional form of electricity is through wires. The continuous research and development has stepped forward a major quantum leap,which aids transmission of electricity without the medium of wires. This paper describes an authentic idea to annihilate the haphazard usage of wires which implicates lot of confusion in particularly regulating them. When we fantasize a future in which transmitting power wirelessly is feasible in cell phones, household robots, mp3 players, laptop computers and other portable electronics which can charge by their own without getting plugged, pardoning us from that eventual, universal power wire.Bulky batteries of these devices might not be even required to operate.Power can be transmitted efficiently upto 95% in this method through non-radiative means.This mechanism mainly involves the principle of using resonance inductive coupling wherein both the transmitter and the receiver operates at resonant frequency.Power transmission gets more efficacious when both the coils are strongly coupled. The transmitter emits a non-radiative magnetic field resonating at KHz frequencies and the receiving unit load resonates in that field.Compared with prevalent magnetic inductive coupling energy transmission devices, the efficiency of the proposed system is much higher.

Abstract: Wireless Power Transmission (WPT) is revolutionizing energy distribution by eliminating the need for physical power cables and enabling seamless, efficient, and sustainable energy transfer across industries. This book explores the fundamental principles, technological advancements, and transformative applications of WPT, including resonant inductive coupling, microwave power transmission, and laser-based energy transfer. It delves into real-world applications such as wireless electric vehicle (EV) charging, consumer electronics, biomedical implants, industrial automation, and space-based solar power. The book also examines the integration of WPT with emerging technologies like 5G, IoT, and smart grids, highlighting its potential to drive a more interconnected and energy-efficient future. Additionally, it addresses economic, environmental, and regulatory considerations, discussing the impact of WPT on energy sustainability, carbon reduction, and policy challenges. Designed for engineers, researchers, policymakers, and technology enthusiasts, this book provides a comprehensive resource for understanding, developing, and implementing next-generation wireless power solutions. Keywords: Wireless Power Transmission, WPT, energy transfer, resonant inductive coupling, microwave power transmission, laser energy transfer, electric vehicle charging, consumer electronics, biomedical implants, smart grids, IoT, 5G, space-based solar power, energy efficiency, sustainable energy, electromagnetic fields, regulatory challenges, emerging technologies, future energy systems.

The growing global population and technological advancements are leading to a sharp increase in energy demand. Simultaneously, energy is being wasted across various domains, particularly in transportation. Harnessing this lost energy and converting it into usable forms is critical for sustainability. This paper presents a novel system for generating power using the pressure exerted by tires of electric vehicles (EVs) via piezoelectric transducers. The generated energy is then wirelessly transmitted to charge EVs, utilizing resonant inductive coupling. This system not only helps recover energy from everyday driving but also offers a potential solution to energy wastage. Experiments demonstrate the feasibility of this approach, with power transmission efficiencies exceeding 90% at moderate distances. Key Words: pressure-based power generation, piezoelectric transducers, wireless power transfer, electric vehicles, resonant inductive coupling, energy harvesting.

<span lang="EN-US">A wireless power transfer system designed for electro-vehicle recharge and low-power device charging is explained in this document through resonant inductive coupling technology. Once switched on the pulse generator and IRF540 MOSFETs from the IC CD4047 drive high-frequency signals through the transmitter coil. IR sensors function as operational safety tools by detecting valid receivers which activate a relay control system for transmitter power management and reduce unnecessary energy consumption. A full-wave rectifier along with the 7805-voltage regulator enables the receiver unit to deliver fully stable 5 V DC output. System status is displayed through a user interface equipped with an LCD and real-time billing information runs on ThingSpeak IoT platform for visualization. Tests show that the system reaches a maximum power transfer efficiency of 90% alongside successful relay operation lasting less than 150 ms. The system provides an inexpensive solution to build smart wireless charging infrastructure networks that remain energy-efficient and expandable through its built-in control and monitoring functions.</span>

The widespread adoption of electric vehicles (EVs) has spurred the development of advanced charging infrastructures that are efficient, intelligent, and user-friendly. Among these, Wireless Electric Vehicle Charging Systems (EVWCS) have emerged as a transformative solution, enabling contactless power transfer through various Wireless Power Transfer (WPT) technologies, such as inductive coupling, resonant inductive coupling, capacitive power transfer, and magnetic gear-based systems. The review will conduct an extensive evaluation of these WPT methods through detailed analysis of their operational mechanisms and their advantages and limitations for both stationary and dynamic charging applications. The paper will examine IoT applications for EV charging system enhancement through smart grid communication and real-time data exchange and cybersecurity protection. The paper also examines the challenges encountered in the implementation of EVWCS which include technical limitations, health and safety issues, electromagnetic compatibility as well as high cost of deployment. Owing to the summary of the main contributions in existing literature, as well as the development of major research gaps, the paper presents articulated approach to future research to implement secure, efficient, and scalable wireless EV charging infrastructures.

This paper presents tuning methods on a Class-E power amplifier for a wireless power transfer (WPT) system based on resonant inductive coupling. In this paper, the scope of research is focusing on providing a stable power for Wireless Capsule Endoscopy (WCE). Shifting of the resonance frequency of a WPT system is unavoidable mainly due to various factors including variations in its working environments. This reduces the performance of WPT system leading to inconsistent voltage at the receiver. To overcome this problem, two tuning approaches namely frequency tuning and voltage tuning are proposed. The Frequency tuning method works to tune the power amplifier circuit so that it operates at the frequency close the resonant frequency of the transmitter which is also ensured the optimal switching condition in the driving circuit. The voltage tuning helps to regulate the receiver’s voltage output to make it stable and constant. Our experimental results indicate that the proposed approach has improved the performance of the WPT.

In this paper the possibility of achieving a coupling-independent operating regime for a Wireless Power Transfer Link based on resonant inductive coupling is theoretically and experimentally investigated. The two different cases of a link using either asynchronous or synchronous resonators are analyzed and discussed. It is shown that a coupling-independent regime can be realized by an appropriate selection of the operating frequency of a synchronous WPT link having a coupling coefficient above a critical value which depends on the resistive load of the link.

The pursuit of energy sustainability has become paramount in addressing the global challenges of climate change, depleting fossil fuel resources, and increasing energy demand. This study explores the convergence of artificial intelligence (AI), energy sustainability, and wireless electricity generation as a transformative pathway toward a resilient and eco-friendly energy future. Energy sustainability involves developing systems that ensure long-term energy availability while minimizing environmental impacts. Traditional energy infrastructures face limitations in efficiency, accessibility, and scalability. Emerging technologies, particularly AI and wireless power transfer (WPT), offer innovative solutions to these constraints. AI plays a pivotal role in optimizing energy systems by enabling real-time data analysis, predictive maintenance, smart grid management, and demand forecasting. Its application enhances decision-making processes and improves system reliability and efficiency. Simultaneously, wireless electricity generation and transmission technologies—such as resonant inductive coupling, microwave power transmission, and laser-based energy transfer—are redefining how energy is transmitted and accessed. These technologies eliminate the need for physical connections, reduce energy losses, and offer scalable deployment in remote and urban settings. The integration of AI with wireless electricity generation facilitates adaptive control systems, fault detection, and dynamic load balancing, significantly improving system performance and sustainability. Furthermore, these systems can be embedded into renewable energy infrastructures, such as solar and wind farms, allowing for seamless and efficient energy delivery to distributed networks and off-grid communities. This synergy not only reduces carbon emissions but also supports the equitable distribution of clean energy resources. The study also evaluates potential challenges including energy loss during transmission, safety concerns, technological standardization, and regulatory frameworks. However, through interdisciplinary innovation and collaboration, these challenges can be mitigated to realize the full potential of AI-enhanced wireless energy systems. This paper contributes to the growing body of research advocating for sustainable energy transitions, emphasizing the critical role of intelligent, contactless power systems.

Wireless power transfer (WPT) is the method to transfer power from the source to load without the use of cables or wires. There are different ways of WPT which can be broadly classified as radiative and non-radiative. The broad category of radiative WPT is microwave whose working frequency is in GHz and light waves or laser having a working frequency in THz. In non-radiative WPT, the transfer of power is basically through magnetic coupling of the transmitter and receiver coils where the maximum power transfer happens at a particular resonant frequency. Inductive and resonant inductive coupling are the two broad categories of non-radiative WPT having a working frequency ranging in Hz-MHz and MHz-GHz, respectively. Since microwaves are less prone to scattering and conversion of microwave energy to electrical energy and vice-versa is relatively easier, microwave WPT is an efficient way of radiative power transfer. The research on different ways of WPT is presented; their drawbacks and future prospective are presented in the paper.KeywordsWireless power transferMetamaterialAntenna

Wirelessly powered ultraviolet light emitting diodes for photocatalytic oxidation

Silicon carbide (SiC) has been extensively investigated in the last decade, specifically for applications in harsh environments. However, most SiC sensors require an external power supply, which cannot operate at high temperatures. This letter develops a new sensing technology in a SiC platform based on near field communication to eliminate the requirement for wired power sources. The 3C-SiC temperature sensors were fabricated from a SiC-on-insulator substrate formed by anodic bonding. The sensors functioned based on the thermoresistance of the SiC films with the high TCR of −13 000 ppm/K at 300 K and −3 000 ppm/K at 600 K. The resistance change of the sensors was wirelessly measured using a reading coil placed outside of the heating chamber, showing a significant resonant-frequency-shift (−400 ppm/K at 600 K) of the coupling impedance under temperature variation. The proposed technique is promising for the development of wireless wide-band-gap sensors used in extreme conditions.

자기 공진 결합 (resonant inductive coupling) 현상을 이용한 무선 전력 전송 기술을 구현하기 위하여 새로운 구조의 자기 공진기를 제시한다. MIT 연구팀이 제안한 헬릭스 (helix) 모양의 자기 공진기의 크기를 줄이고, 공진 주파수 10 MHz를 유지하며, 무선 전력 전송 효율이 크게 열화 되지 않도록 설계한다. 새로운 구조의 자기 공진기는 스파이럴 (spiral) 모양으로써 헬릭스 모양 대비 소형화를 달성하였다. 스파이럴 모양 (<TEX>$1,696cm^3$</TEX>)의 자기 공진기는 헬릭스 모양 (<TEX>$59,376cm^3$</TEX>) 대비 97% 소형화를 이룩하였고, 무선 전력 전송 효율은 기존 기술 (2 m 거리에서 40 % 전송 효율) 대비 9% 이하로 차이를 줄임으로써 무선 전력 전송 기술의 실용화에 기여할 수 있게 되었다. A novel inductive resonator for the implementation of wireless power transfer using resonant inductive coupling is presented. The proposed inductive resonator is much smaller than the helix shape resonator suggested by MIT research team but operates the same resonant frequency with comparable wireless power transfer efficiency. The proposed inductive resonator is a spiral shape (<TEX>$1,696cm^3$</TEX>), which is 97 % smaller than the helix shape (<TEX>$59,376cm^3$</TEX>). The wireless power transfer efficiency is less than 9 % when compared to the helix shape resonator. With the reduce size and comparable efficiency, this novel inductive resonator can be used in practical application of wireless power transfer.