Wireless Powering of Brain Implants with Ultrasound

We have seen an incredible transition in computing devices from vast compute servers that filled a whole room towards personal computers, laptops, tablets and smartphones. A similar revolution is happening in the medical diagnostic & therapeutic world. Recent years have seen a rapid rise of advanced (wearable) medical devices that bring high-quality medically-relevant diagnostics to an ever more convenient form factor at an ever lower cost. More recently a shift is witnessed towards advanced implantable devices that require minimally invasive procedures for their placement. Examples include ingestibles, injectables, endoscopically implanted devices and subcutaneous implants. One of the biggest challenges to overcome in such highly miniaturized devices is the problem of power delivery. Most of the solutions today are either wired or battery-powered which has several severe limitations (toxicity, patient safety and size/volume). Hence there is a major interest to develop implants that can be wirelessly powered. In this area, inductively coupled devices are the most prevalent, but they rely on large coils. RF-based wireless powering on the other hand is not efficient for deep implants due to the absorption of RF waves by human tissue. Ultrasound powering however is a very interesting technique for medical implants. Ultrasound waves, already widely used for imaging, are safe and are less absorbed by the human tissue than RF waves. Efficient ultrasound transducers can be made very small and even integrated into a chip in phased arrays to perform acoustic beam forming. In this PhD, the candidate will develop active and passive acoustic beam forming approaches for the wireless powering of brain-implanted devices. He will use power link budget comparison as a tool for ranking configurations with smart/agile ultrasound source and/or receiver and assess benefits of active or passive probe tracking. This assessment will include not only the simulation of acoustic fields through skin/skull/tissues and brain-itself, but also novel acoustic transducers developed at imec (p/cMUTs) and their support electronics. The key will be to develop a scalable approach for powering large amount of separated small brain implants, thus using a form of acoustic hologram, distributing acoustic intensity in 3D in a controllable fashion. The outcome of this PhD will allow dramatically smaller implants paving the way for true minimally invasive solutions. The work will be integrated and demonstrated in a proof-of-concept device.