Medical implants powered by radio waves have been successfully tested

A medical implant the size of a grain of rice which is powered by radio waves from outside the body has been successfully tested opening the way to smaller longer lasting devices for treating a wide variety of ailments.

Pacemakers and brain implants for Parkinson’s disease, for example, use batteries that are implanted along with the active devices. The batteries limit how long the devices can be used for and replacing them requires surgery. Batteries also make up a large part of any implant’s size and weight. Removing the battery immediately shrinks the implant. These smaller devices could release drugs slowly deep in the body, provide a burst of electricity in the brain for treating Parkinson’s, or a pulse of light for other neurological ailments. While the tested prototype was the size of a grain of rice, researchers believe they can make even smaller implants.

“These devices could be compatible with sensing conditions [for detecting ailments] as well as aiding in the delivery of a drug,” said Giovanni Traverso, an assistant professor at Brigham and Women’s Hospital.

Brigham and Women’s Hospital researchers and MIT scientists have developed a way to power and communicate with devices implanted deep within the human body. Credit: MIT

In tests in pigs, researchers demonstrated how radio waves can deliver power from a distance of one metre to devices 10 centimetres inside tissue. They have concluded that for implants just beneath the surface of the skin, power could be transmitted up to 38 metres away. As well as receive power, the implants can use that energy to transmit data back to the medical staff. “Having the capacity to communicate with these systems without the need for a battery would be a significant advance,” said Traverso. Radio frequency identification (RFID) technology could also benefit from a wireless power system for longer distance tracking, transmitting its information over a greater distance.

The problem the researchers needed to overcome was the fact that radio waves dissipate as they pass through flesh and bone and cannot deliver enough energy to power any kind of implant. The solution was to use an array of antennas that emit radio waves of slightly different frequencies. These different radio waves overlap and combine and at the point where they overlap they provide enough energy to power an implant. The scientists call this antenna system, in vivo networking (IVN). With this IVN, power transmission system, the precise location of the sensors does not need to be known. The multiple power transmissions also mean that several devices in different parts of the body can be powered at once.

At Brigham and Women’s Hospital various ingestible devices that could monitor the gastrointestinal tract, record vital signs and deliver drugs are being developed. Other work includes making the transmission of the power possible over greater distances and making its delivery more efficient. The research has been funded by the United States government’s National Institutes of Health and Massachusetts’ Institute of Technology’s Media Lab Consortium.

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