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The interactions of medical implants in the human body with electromagnetic fields from newly introduced high-field technologies such as near-field wireless power transfer (WPT) are of great concern. In this study, the effects of implants on the specific absorption rate (SAR) in a head model were computationally evaluated in the immediate vicinity of a WPT system operating at 6.78 MHz with a transferred power of 50 W. The SAR in the head model located 30 mm above the WPT system was evaluated with a skull plate, bone plates (different shapes), miniplate, fixtures, and a deep brain stimulator. The results indicated that even small implants had notable effects on the SAR distribution and corresponding local peak and mass-averaged SAR values. Apart from the size and shape of the implant, the crucial factor influencing the SAR was the implant’s position with respect to the WPT system. Therefore, various position configurations were simulated for the WPT system to determine the worst case scenario for each specific implant. Although the local peak SAR value was increased by a factor of 600 in the worst-case scenario (for the skull plate), the SAR $_{\text{1}g}$ and SAR $_{\text{10}g}$ were only increased by factors of seven and four, respectively. Compliance with international safety limits was studied, followed by computing the maximum allowable transmit power (MATP). It was found that, without the implant, the MATP satisfying SAR $_{\text{1}g}$ was 43 W for the designed WPT system, and was reduced to 6.9 W in the presence of the skull plate. [ABSTRACT FROM AUTHOR]

An efficient noninvasive system for simultaneous transmission of wireless power and data is vital for continuous human health monitoring. In this article, we present a self-tuned spiral-shaped antenna with dual-band characteristics operating at 920 MHz and 2.4 GHz for efficient wireless power transfer (WPT) and data telemetry, respectively. To avoid vision blockage, the proposed smart contact lens (SCL) dipole antenna comprises two symmetrical spiral arms with inner and outer diameters of 10 and 14 mm, respectively. The SCL antenna was printed on a thin flexible polyimide substrate with a biocompatible polydimethylsiloxane (PDMS) coating. The influence of dispersed dielectric properties of PDMS on SCL antenna performance was investigated. Furthermore, the antenna was combined with a miniaturized rectifier and a micro-LED to demonstrate wireless LED illumination on a saline-filled model head. The power transfer efficiency (PTE) as a function of eye movement in the form of a path gain was also investigated. In addition, the PTE across the distance variations from 10 to 30 mm was computed, and a −17.85 dB was achieved at a separation of 12 mm. A specific absorption rate analysis was performed to determine human eye safety under radio frequency exposure from the external transmitter and the results complied with the International Commission on Non-Ionizing Radiation Protection guidelines. Furthermore, a theoretical link power budget analysis was experimentally validated using software-defined radio. Measurements of s-parameters were noted through the use of a saline solution to mimic a realistic human eye and were found to have a reasonable correlation with the simulated results. [ABSTRACT FROM AUTHOR]

Advancement in the technology of leadless cardiac pacemakers (LCPs) has led to ultracompact designs of implantable antennas. In this study, a small-sized antenna for integration with an LCP, which can be operated in the industrial, scientific, and medical (ISM) band of 2.4 GHz, is developed. The proposed antenna was constructed in a spiral shape to provide superior miniaturization, less sensitivity to body tissue variation, and low specific absorption rate (SAR) values, and avoid fabrication complexities due to its small size. The antenna with a footprint of $3 \times 4\,\,\times0.5$ mm3 was constructed on a high dielectric material, namely, Rogers RT/duroid 6010. To the best of the authors’ knowledge, this is the smallest footprint with enhanced performance when compared to previous reports related to implantable antennas. In addition, the antenna was integrated with a 3-D printed LCP having dummy electronics and experimentally validated in saline solution and minced pork. The antenna sustained good impedance matching at the ISM band with a measured bandwidth of 21.88% and 15.46% with the device and without the device, respectively. Due to the smooth electric field (surface currents) over the patch, the antenna system had 270.28 and 31.04 W/kg peak SAR for 1 and 10 g of tissues, respectively, with a maximum peak gain of −25.95 dBi. We also discussed the effects of a coaxial cable and the antenna orientation on its performance. From the measured received signal strength, a stable biotelemetric link can be established between the implant and external controlling device up to a distance of 2 m. [ABSTRACT FROM AUTHOR]