Abstract
Wireless power transfer (WPT) presents a safe and robust method for powering biomedical implants. The range and misalignment tolerance restrictions of the WPT system are the main factors, conducive to the transfer efficiency degradation. Especially, the implanted device is invisible and difficult to arrange in alignment with the transmitting coil. This paper proposes a butterfly-shaped transmitting (BS-Tx) coil of a magnetic resonance WPT system for biomedical implants. The BS-Tx coil prototypes with the changing driven current directions, parallel and anti-parallel current directions, are verified and analyzed. Besides, an equivalent circuit model of a coupling two-coil system with an optimal pair of capacitors method for the matching network is mathematically derived to obtain the maximized power transfer efficiency. The BS-Tx coil enhances the efficiency of the system in the distance, angle, and axial misalignment tolerances. A practical WPT system is fabricated and measured to verify the transfer efficiency through the real biological tissue and exhibits a significant efficiency improvement. Finally, a hypothetical context of retinal prosthesis application is demonstrated as a potential application to retinal implants. The proposed system shows a low specific absorption rate, that is satisfied the human safety regulations.
Highlights
Wireless power transfer (WPT) system presents an emerging and promising way to provide a safe and convenient solution for the power supply of biomedical implants, which has attracted a lot of attention in recent years [1]–[5]
A change of the transmitting (Tx) coil structure based on a butterfly shape is presented to overcome the efficiency degradation of a WPT system with variations in transfer distance, angle and axis misalignment
In [21], a BS-Tx coil of a magnetic resonance WPT system for miniaturized biomedical implants was proposed, which can improve the efficiency in the various position of a 9-mm diameter receiver coil
Summary
Wireless power transfer (WPT) system presents an emerging and promising way to provide a safe and convenient solution for the power supply of biomedical implants, which has attracted a lot of attention in recent years [1]–[5]. A change of the transmitting (Tx) coil structure based on a butterfly shape is presented to overcome the efficiency degradation of a WPT system with variations in transfer distance, angle and axis misalignment. In [21], a BS-Tx coil of a magnetic resonance WPT system for miniaturized biomedical implants was proposed, which can improve the efficiency in the various position of a 9-mm diameter receiver coil. The BS-Tx coil was only considered the flowed current driven in the same direction in each loop, leading to the same direction of the magnetic field vectors. The SCSM structure presents the magnetic field synthesis that is focused and forwarded to the receiving area leading to the significant enhancement in the further transfer distance.
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