New MIT system wirelessly powers medical implants using radio waves
While research is booming in the field of ingestible medical implants, a major challenge still to be overcome is working out how to power these tiny devices when they are deep inside a human body. Traditional batteries are large, contain toxic chemicals, and need to be periodically replaced, but new research from MIT and Brigham and Women's Hospital has demonstrated a way to power implanted devices using radio waves.
For some years, researchers have known that ambient radio waves can be hijacked to generate tiny amounts of power for small devices. The hurdle in translating that technology into implantable devices is that these waves generally don't penetrate very far into human tissue.
Last year, a team composed of researchers from MIT, Harvard, and Brigham and Women's Hospital first demonstrated an innovative new way to power implants using radio waves. That technique, called mid-field coupling, successfully delivered power to several antennas inside an animal model at levels high enough to run a range of medical devices.
This earlier study still needed its external transmission device to sit on the skin outside of the body. Now, in new research to be presented at the Association for Computing Machinery Special Interest Group on Data Communication (SIGCOMM) conference in August, the team has refined the technology to show that devices as deep as 10 cm (3.9 in) inside a body can be effectively powered from a distance of 1 m (3.2 ft).
The new system is called "In Vivo Networking" (IVN) and it involves emitting several radio waves at differing frequencies.
"We chose frequencies that are slightly different from each other, and in doing so, we know that at some point in time these are going to reach their highs at the same time," explains Fadel Adib, senior author on the new study. "When they reach their highs at the same time, they are able to overcome the energy threshold needed to power the device."
The prototype tested in this new study was about the size of a grain of rice but the researchers suggest it could be made even smaller. This means the technology may be adapted to not only medical devices like ingestible implants that deliver drugs or monitor internal vital signs, but also wireless brain implants designed to modulate neural activity through optogenetics.
The new system also may have uses beyond medical implants. The study suggests the IVN method could be applied to powering passive RFIDs at distances up to 38 m (124 ft), which could be useful for smart inventory systems in warehouses.
Take a closer look at the new study in the video below.