Multimodal Wireless Implantable Medical Device (MW-IMD) Platform

Abstract

Implantable medical devices (IMDs) have advanced significantly in the last few decades due to innovations in microelectronics and power sources. Today, IMDs can perform various vital functions such as stimulating muscular organs (e.g., heart, bladder, neurons) to maintain the body mechanics and regulating physiological fluid (e.g., blood, hormone, urine, etc.). All of these effectively improve the quality of life and prolong life expectancy. However, many existing IMDs often blindly deliver therapeutic means without knowing the state of the disease. Since IMDs are usually surgically introduced to the human body, post-operation adjustments are difficult, resulting in chronic stimulation. As such, the long-term operation of IMDs shall be precisely regulated based on the current state of the body, i.e., closing the loop, especially with unprecedented communication and powering techniques. The goal of this research is to develop an implantable medical device (IMD) platform that can close the loop not only between sensing and stimulation within the IMD itself but also between other IMDs and the outside world. Thus, we first demonstrate a standalone closed-looped IMD that regulates oxygen generation based on physiological levels. Second, the IMD platform can also bridge other passive implantable sensors to the outside world. To this end, this report discusses a passive sensor in the form of a Smart Stent that senses and transmits arterial blood pressure information to the IMD platform via magnetic resonance (MR) coupling. Therefore, such MR coupling intrabody communication in the body is rigorously investigated. Lastly, we report an effective and efficient powering technique for the IMD platform. Ultrasonic waves in the human body can travel long distances with relatively low attenuation, reaching deep tissue. In this thesis, we enhance the ultrasonic powering method for IMDs with a novel receiver design for omnidirectional powering. Overall, the proposed multifunctional, multimodal, wireless IMD platform can operate reliably for the long term due to novel MR coupling communication and omnidirectional ultrasonic powering.