Magnetic resonant-based wireless power transfer system (WPTS) is an efficient way to energize critical biomedical devices, such as wireless capsule endoscopes, where a direct wire connection is not practical. However, low power transfer efficiency (PTE) and poor received power stability (RPS) are usually the main bottlenecks of WPTS in this application. Thus, this paper proposes an efficient WPTS that tremendously improves the PTE and enriches the RPS. In order to improve the PTE, an optimum three-coil inductive link is adopted with a compact wearable power transmitting coil-I (PTC-I) and a 2-3D power receiving coil. As a result, the stability is improved with the new configuration of the power transmission coil-III (PTC-III) and power combining technique at the receiving side. To confirm the validity of the proposed design, proof-of-concept prototypes were implemented for an experimental test. Results obtained from the experimental test assured that the proposed PTC-I-based system achieved a PTE of more than 8% while transferring 758 mW of power with 68.7% RPS. The best overall RPS attained by the proposed PTC-III based system is 79.2%. This system achieved a PTE of 5.4% transferring at least 570 mW of power. In comparison, the performance of the proposed designs greatly outweighs the previous designs.

Magnetic resonance-based wireless power transfer system offers a promising solution to overcome power limitations typically encountered by capsule endoscopy. Despite of much attention in this area, aspects such as power stability and power transfer efficiency remain suboptimal and therefore investigation for further improvement is still required. This paper presents a method to improve power stability as well as power transfer efficiency for wireless capsule endoscopy. A new power transmission coil capable of producing uniform magnetic field is proposed to improve power stability through uniform field that at the same time minimizes the unnecessary peak electromagnetic exposure. To improve power transfer efficiency, a mixed resonance scheme is employed. Our experimental results show improvement over existing methods where the proposed system attained power stability of 94.62% and power transfer efficiency of 4.9% under worst position of the receiving coil. Furthermore, the proposed transmitting coil provides additional advantage, where it minimized the unnecessary peak electromagnetic exposure by 26% as compared to the conventional Helmholtz coil-based system. We believe the proposed system will open new direction for future wireless capsule endoscopy and can also be useful in other industrial applications.

Wireless capsule endoscope (WCE) is a notable invention introduced in the biomedical industry. It involves swallowing a small disposable video capsule that takes photographic images as it passes through the gastrointestinal (GI) tract. WCE allows physicians to visualize and diagnose disorders covering the full length of the GI tract. Although WCE can provide useful images of the internal GI tract, the identification of the exact location of the detected disease remains unclear. Location information is very crucial for the subsequent treatment of the detected disease either through surgery or through local drug delivery. The huge potential of WCE in future endoscopic practice relies on the successful tracking of the wireless capsule. This paper presents a comprehensive systematic review on the recent developments in WCE localization techniques that have been reported in credible sources, namely, IEEE Xplore, PubMed, Scopus, Science Direct, Springer Link, and Google Scholar. Detailed analysis and systematic comparison are provided to highlight the achievement and future direction of WCE localization. This paper can be a valuable source of reference and guidance for future research in this field.

Wireless capsule endoscopy (WCE) is a promising technology for direct diagnosis of the entire small bowel to detect lethal diseases, including cancer and obscure gastrointestinal bleeding (OGIB). To improve the quality of diagnosis, some vital specifications of WCE such as image resolution, frame rate and working time need to be improved. Additionally, future multi-functioning robotic capsule endoscopy (RCE) units may utilize advanced features such as active system control over capsule motion, drug delivery systems, semi-surgical tools and biopsy. However, the inclusion of the above advanced features demands additional power that make conventional power source methods impractical. In this regards, wireless power transmission (WPT) system has received attention among researchers to overcome this problem. Systematic reviews on techniques of using WPT for WCE are limited, especially when involving the recent technological advancements. This paper aims to fill that gap by providing a systematic review with emphasis on the aspects related to the amount of transmitted power, the power transmission efficiency, the system stability and patient safety. It is noted that, thus far the development of WPT system for this WCE application is still in initial stage and there is room for improvements, especially involving system efficiency, stability, and the patient safety aspects.

Bulky off-chip inductors are predominantly adopted for inductive-based step-up DC-DC converter in RF energy harvesting (RFEH) systems, which impose a restriction in physical form factor for miniaturized device. This article review and explores the capacitive-based step-up DC-DC converters (charge-pump) as voltage boosting element for low-voltage RFEH systems. An overview of RFEH is established and a comprehensive review of CMOS charge-pump is followed along with the complementary frequency generation circuit used as a clocking element. Key design considerations of charge-pump circuits are included here along with recommendations to circumvent its bottlenecks for future development in RFEH systems.

Wearable and implantable medical devices (IMDs) have come a long way in the past few decades and have contributed to the development of many personalized health monitoring and therapeutic applications. Sustaining these devices with reliable and long-term power supply is still an ongoing challenge. This review discusses the challenges and milestones in energizing wearable and IMDs using the RF energy harvesting (RFEH) technique. The review highlights the main integrating frontend blocks such as the wearable and implantable antenna design, matching network, and rectifier topologies. The advantages and bottlenecks of adopting RFEH technology in wearable and IMDs are reviewed, along with the system elements and characteristics that enable these devices to operate in an optimized manner. The applications of RFEH in wearable and IMDs medical devices are elaborated in the final section of this review. This article summarizes the recent developments in RFEH, highlights the gaps, and explores future research opportunities.