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Overview
A research project by MIT and Brigham and Women's Hospital has developed a method to power and communicate with implantable devices. These devices, powered by radio waves rather than batteries, can deliver drugs, monitor internal conditions, or stimulate the brain with electrical currents and light to treat disease.
Device Miniaturization
According to reports, these implants can be transmitted safely through body tissue, and because they require no battery their size can be reduced. The prototypes used in tests were about the size of a grain of rice, and are expected to be further miniaturized.
Research Team and Targets
Fadel Adib, an assistant professor at the MIT Media Lab, said that although these micro-implants have no battery, they can still communicate over long distances from outside the body, opening new possibilities for medical applications. Implantable medical devices offer clinicians new ways to diagnose, monitor, and treat disease.
Assistant professor Giovanni Traverso said the lab is currently studying various bioresorbable systems for drug delivery, vital-sign monitoring, and detecting gastrointestinal motility.
Motivation: Limitations of Current Implants
Currently, implanted medical devices such as pacemakers include batteries that occupy most of the device volume and have limited lifetimes. Electrodes implanted in the brain that deliver currents are used in deep brain stimulation, typically to treat Parkinson's disease or epilepsy. Those electrodes are controlled by a subcutaneously implanted unit; if a wireless power source were used, the unit could be replaced.
How the IVN System Works
Radio waves attenuate when passing through the body, so they may not provide sufficient power. To address this, the researchers designed an in-body network system called IVN. The system relies on an antenna array that emits radio waves with slightly different frequencies; as the waves propagate they interfere and combine in different ways, and specific focal points where peaks overlap can deliver enough energy to power implanted sensors.
Because the new system transmits power over a larger area, the researchers do not need to know the exact location of the sensors inside the body and can power multiple devices at once. When a sensor receives power, it also receives a signal instructing it to send information back to the antennas; that signal can also trigger drug release, increase current, or emit pulsed light.
Test Results
In tests on pigs, the researchers found that the radio waves could deliver power from 1 meter outside the body to sensors located 10 centimeters deep. If the sensor is very close to the skin surface, the radio waves could power it from as far as 38 meters.
Potential Applications
Adib said that implant depth affects remote power range; researchers are working to improve power transfer efficiency and extend range. The technique could improve other RFID applications, such as inventory control, retail analytics, and smart environments, enabling longer-range object tracking and communication.
