Design and In-Vivo Test of Battery-Free Implantable Temperature Sensor Based on Magnetic Resonant Wireless Power Transfer

The in-body operation of implantable medical devices (IMDs) bring the challenge of delivering power conveniently and safely from outside of the body-contact distance through obstacles, including skin and tissue. Magnetic resonance-based wireless power transfer (WPT) provides a promising solution for IMDs, featured by its high-power transfer efficiency at midrange distances. However, to our knowledge, very few works have investigated the performance of the resonance-based method for transferring power to sensors in vivo. Therefore, in this paper, we design an IMD powered by a WPT system and carry out an in-vivo experiment on the device. This IMD is a Bluetooth module integrated with a temperature sensor and its power is provided by a 3-coil magnetic resonance-based WPT system without batteries. Through the in-vivo experiment on a pig, we successfully apply the WPT system to power the implanted sensor for wireless in-body temperature monitoring. The results demonstrate that the examined 3-coil coupled magnetic resonance WPT method can meet the power requirement and ensure the functional operations of the implanted temperature sensor. Consequently, the capability and feasibility of the magnetic resonance approach for powering in-vivo IMDs are verified, paving the way for the future design and applications of implantable sensors.