Biomedical WPT Group
Patients who require implantable medical devices such as pacemakers and spinal cord stimulators have to undergo surgery to replace batteries and to secure power sources by wiring from outside the body, which imposes a great physical and mental burden. To improve the quality of life (QoL) of such patients, we are conducting research on wireless power transmission for implantable medical devices from outside the body.
We are developing a capacitive WPT system with power supply circuits and transmitters mounted on film electrodes so that implantable medical devices can be recharged during daily life. Power is supplied through multiple biological tissues, including skin, subcutaneous fat, and muscle, and the thickness of each tissue varies within an area. The thickness of each tissue has also in-plane variation and there are extra-muscular fat and other substances. So, it cannot be neatly separated into skin, fat, and muscle. Therefore, we measure the complex permittivity from the skin surface to the surface of medical devices implanted in the body and design a system using a high-precision equivalent circuit that we have constructed ourselves.
Our goal is to create a disposable device that can be attached to the body surface with a small battery, power supply circuit, and power transmitter to supply power to an implantable medical device, and then peeled off and discarded when recharging is complete. This will make it possible to provide devices that can be recharged 24 hours a day, 7 days a week, anywhere.
We have measured the complex permittivity of multiple biological tissues along the power supply path, designed the power transmitting and receiving electrodes based on this data, and achieved power transmission that can drive a pacemaker in compliance with the IEEE C95.1 2019 Guideline for Protection of the Human Body against Radio Waves while using an electric field method. Currently, we are researching the further improvement of efficiency and a power transmission circuit that generates less heat.
T. Segawa, R.i Aoyama, M. Tamura, “Electrode Design Theory Using Highly Accurate Equivalent Circuits in Biological Capacitive WPT,” IEEE Microw. Wirel. Techn. Lett., vol. 33, no. 6, pp.943-946, Jun. 2023.
M. Matsumoto, M. Tamura, “Coupler Design and Analysis of Capacitive Wireless Power Charging for Implantable Medical Devices,” IEICE Trans. Electron., vol. E105-C, no. 9, pp.398-406, Sep. 2022.
M. Tamura, T. Segawa, M. Matsumoto,“Capacitive Coupler for Wireless Power Transfer to Intravascular Implant Devices,” IEEE Microw. Wirel. Compon. Lett., vol. 32, no. 6, pp.672-675, Jun. 2022.
M. Tamura, K. Murai, M. Matsumoto, “Design of Disposable Film-Type Capacitive Wireless Charging for Implantable Medical Devices,” in Proc. 2021 IEEE MTT-S Int. Microwave Symposium, Atlanta, GA, Jun. 2021, pp.58-61.