Ultrasonically Rechargeable Platforms for Closed-Loop Distributed Sensing and Actuation in the Human Body

In the near future, innovative medical therapies will be administered by means of intra-body wireless sensor networks of implantable medical devices (IMDs). However, realizing wireless networks with traditional implantable biosensors and actuators is challenging, because (i) they often rely on wired connections that are invasive and prone to infections; and (ii) they are powered by batteries that occupy most of the device volume and have a relatively short lifetime. This article reports on the design of a system of interconnected implantable nodes that leverage ultrasonic wireless propagation to (i) be remotely recharged, removing the need for batteries; (ii) to create wireless communication links avoiding wires or radio-frequency (RF) connections that have poor performance when operating in tissues. We illustrate the design of the core building blocks to realize ultrasonically rechargeable medical sensors and actuators equipped with ultrasonic connectivity. We further demonstrate their use in a practical implementation of a sensing/actuation closed-loop system with distributed sensor nodes. We also develop and experimentally validate a mathematical model to predict the system performance.