In collaboration with researchers from Brigham and Women’s Hospital, MIT researchers have devised a novel method to power and communicate with devices that are implanted deep inside the human body.
Such devices can possibly be used for delivering drugs, tracking conditions within the body, or treating various diseases by activating the brain with light or electricity. Radio frequency waves, which can safely pass via the human tissues, power these implants. The researchers conducted tests in animals and demonstrated that radio frequency waves are capable of powering devices situated 10 centimeters deep within the tissue, from a 1 meter distance.
“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,” states Fadel Adib, senior author of the paper and assistant professor in MIT’s Media Lab. The paper will be presented at the Association for Computing Machinery Special Interest Group on Data Communication (SIGCOMM) conference in August 2018.
Since the devices do not need a battery, they can be very small. In this research, the scientists tested a model which is roughly the size of a grain of rice, but they believe that it can possibly 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,” states Giovanni Traverso, an author of the paper and an assistant professor at Brigham and Women’s Hospital (BWH), Harvard Medical School, a research affiliate at MIT’s Koch Institute for Integrative Cancer Research.
Media Lab postdoc Yunfei Ma, Koch Institute and BWH affiliate postdoc Christoph Steiger, and Media Lab graduate student Zhihong Luo are other authors of the paper.
Implantable or ingestible medical devices in the human body could provide physicians innovative ways to detect, monitor, and treat various diseases. Currently, Traverso’s laboratory is working on different types of ingestible systems that can be used for delivering drugs, detecting movement of the GI tract, and monitoring vital signs.
Implantable electrodes that send an electrical current to the brain are used for a technique called deep brain stimulation. This technique is generally used for treating epilepsy or Parkinson’s disease. A device resembling a pacemaker is implanted under the skin and this device currently controls the electrodes. However, if wireless power is employed, this device can be eliminated. In addition, wireless brain implants could make it possible to deliver light to either inhibit or activate neuron activity via optogenetics. However, this method is yet to be applied in humans but could prove useful for treating a number of neurological conditions.
At present, pacemakers and other implantable medical devices carry their own batteries, which take up most of the space available on the device and provide only a short lifespan. Adib has envisioned much tinier, battery-free devices and has been studying the possibility of using radio waves, which are produced by antennas outside the body, to wirelessly power the implantable devices.
So far, this has been hard to achieve because when radio waves travel through the body, they tend to dissipate and hence they end up being relatively weak to deliver sufficient amount of power. To resolve this issue, the scientists developed a unique system which they termed “In Vivo Networking” (IVN). This novel system depends on a range of antennas that produce radio waves that have somewhat varying frequencies. When these radio waves travel, they overlap and integrate in various ways. At specific points, where the waves’ high points overlap, they can supply energy that is sufficient 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,” says Adib.
Now, with the latest system, the researchers do not have to know where the sensors are exactly located in the body, because the power is transmitted across a large region. This also means that multiple devices can be powered at once. Simultaneously, as the sensors receive a burst of power, they also get a signal that tells them to transmit information back to the antenna. According to the researchers, this signal could even be used to trigger a burst of electricity, release of a drug, or a pulse of light.
Next, the researchers conducted tests in pigs and subsequently demonstrated that it is possible to send power from a distance of 1 meter outside the body, to a sensor located 10 centimeters deep within the body. The sensors can be powered from up to 38 meters away, if they are placed very close to the surface of the skin.
“There’s currently a tradeoff between how deep you can go and how far you can go outside the body,” Adib says.
Currently, the researchers are working to make the power delivery more efficient and transfer it across greater distances. This novel technology also holds the potential to enhance RFID applications in other areas, for example, “smart” environments, retail analytics, and inventory control, enabling tracking and communication of longer-distance objects, say the researchers.
The Media Lab Consortium and the National Institutes of Health funded the research.