Wireless radio system powers devices implanted inside the human body
Image credit: MIT
Medical devices implanted inside the human body could be wirelessly powered and communicated with thanks to a new technology that could revolutionise remote control of drug delivery, sensing, and other medical applications.
Massachusetts Institute of Technology (MIT) researchers developed the implants, which are powered by radio frequency waves and can safely pass through human tissues.
Using an animal model, the researchers demonstrated that the waves can power devices located 10 centimetres deep in tissue, from a distance of one meter.
“Even though these tiny implantable devices have no batteries, we can now communicate with them from a distance outside the body. This opens up entirely new types of medical applications,” said Fadel Adib, an assistant professor in MIT’s Media Lab.
As they do not require a battery, the devices can be made tiny. In this study, the researchers tested a prototype about the size of a grain of rice, but they anticipate that it could be made even smaller.
“Having the capacity to communicate with these systems without the need for a battery would be a significant advance. These devices could be compatible with sensing conditions as well as aiding in the delivery of a drug,” said assistant professor Giovanni Traverso.
Medical devices that can be ingested or implanted in the body could offer doctors new ways to diagnose, monitor, and treat many diseases.
Traverso’s lab is now working on a variety of ingestible systems that can be used to deliver drugs, monitor vital signs, and detect movement of the gastro-intestinal tract. In the brain, implantable electrodes that deliver an electrical current are used for a technique known as deep brain stimulation, which is often used to treat Parkinson’s disease or epilepsy.
These electrodes are now controlled by a pacemaker-like device implanted under the skin, which could be eliminated if wireless power is used. Currently, implantable medical devices, such as pacemakers, carry their own batteries, which occupy most of the space on the device and offer a limited lifespan.
Until now, powering the devices wirelessly has proved difficult to achieve because radio waves tend to dissipate as they pass through the body, so they end up being too weak to supply enough power.
To overcome this problem, the researchers devised a system that they call “In Vivo Networking” (IVN). This system relies on an array of antennae that emit radio waves of slightly different frequencies. As the radio waves propagate, they overlap and combine in different ways. At certain points, where the high points of the waves overlap, they can provide enough energy to power an implanted sensor.
“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,” Adib said.
With the new system, the researchers do not need to know the exact location of the sensors in the body, as the power is transmitted over a large area. This also means that they can power multiple devices at once. At the same time that the sensors receive a burst of power, they also receive a signal telling them to relay information back to the antenna. This signal could also be used to stimulate release of a drug, a burst of electricity, or a pulse of light, the researchers say.
In tests in pigs, the researchers showed they could send power from up to a meter outside the body, to a sensor that was 10 centimetres deep in the body. If the sensors are located very close to the skin’s surface, they can be powered from up to 38 meters away.
The researchers are now working on making the power delivery more efficient and transferring it over greater distances.
This technology also has the potential to improve RFID applications in other areas such as inventory control, retail analytics, and “smart” environments, allowing for longer-distance object tracking and communication, the researchers say.