Implantable devices can do a lot of good for a variety of medical applications. They can be sensors that record and report on various conditions and events within a patient’s body. They can also provide stimulation to power a heart’s pacemaker, or treat conditions ranging from chronic pain to Parkinson’s Disease. But they all pose a similar problem; they need some way to provide electrical power to the device. The traditional method is to use bulky batteries that must be replaced. Energy harvesting technologies are being developed to extract power directly from the patient’s body, but researchers at Stanford University are exploring a different approach.
They want to transmit power wirelessly to the device, in much the same way that a cordless toothbrush gets recharged just by sitting on its stand. (If you look at one closely, you’ll see that there are no electrical contacts, which is a good thing given how water can be splashed around a bathroom sink.) The problem is that this sort of wireless transfer has a limited range, and can’t reach deeper into the patient’s body than much below the skin. If you crank up the emitted power, you risk doing harm to the biological tissues in the body. Some researchers have experimented with coils to induce a current from a wireless source, but these have to be about a half-inch in diameter to work, which limits their practical use as implants.
The Stanford scientists have found a way to transmit power effectively to a tiny coil encased along with microelectronics to create useful devices no bigger than a grain of rice. The system uses an array of antennae in a thin patch on the patient’s skin to send emissions that can be focused on the implant’s location. This array can then be powered by traditional batteries or other power sources. The result is an implant that does not require batteries and that can perform its function for years without needing to be disturbed. It could open up entirely new avenues for treatment of a range of conditions.