(Image courtesy MIT.)
A team of researchers at Massachusetts Institute of Technology (MIT), working with scientists from Brigham and Women’s Hospital (BWH) in Boston, have developed a new way to power and communicate with implanted medical devices. They have designed implants powered by radio frequency waves which can safely pass through human tissue. In animal tests, the researchers demonstrated that the radio frequency waves can power devices up to 10 centimeters deep in living tissue, from a distance of one meter away. Devices just under the surface of the skin could be powered from up to 38 meters away.
The principal difficulty in using radio waves is that the waves tend to dissipate as they pass through the body—making them too weak to supply enough power. The researchers have devised a system they call “In Vivo Networking” (IVN) to overcome this tendency. IVN relies on a series of antennas that emit radio waves at slightly different frequencies. As the radio waves travel, their high points will sometimes overlap. When this overlapping occurs at an implant, enough energy can be provided to power the implant.
“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. When they reach their highs at the same time, they are able to overcome the energy threshold needed to power the device,” says Fadel Adib, assistant professor in MIT’s Media Lab and a senior author of the paper.
The array would transmit those radio waves over a relatively large area, meaning the researchers don’t need to pinpoint the exact location of the devices in the body. This array also allows for the charging of several devices at once. The radio signals could also be used to transmit instructions to the implants to release a drug, a burst of electricity or a pulse of light.
Because the devices do not need a battery, they can be much smaller—in fact, researchers have tested a prototype about the size of a grain of rice, but they predict it can be further miniaturized.
Medical devices that can be swallowed or implanted in the body—and that could be charged and controlled through radio waves—could offer doctors new ways to diagnose, monitor, and treat many diseases.
Read more about engineering-inspired advancements in medical implant technology at Engineering Surgical Implants that Grow with Children.