The research was presented at IEEE’s International Microwave Symposium (IMS) 2017, in Honolulu, Hawaii last week.
The pacemaker designed by professor Aydin Babakhani at the Rice lab of electrical and computer engineering, harvests energy wirelessly from radio frequency radiation transmitted by an external battery pack. In the prototype presented at IMS, the wireless power transmitter can be placed up to few centimeters away.
Pacemakers use electrical signals to prompt the heart to keep a steady beat, but they’ve traditionally not been implanted directly into a patient’s heart. Instead, they’re located away from the heart, where surgeons can periodically replace their onboard batteries with minor surgery; their electrical signals are transmitted to the heart via wires called “leads.”
Some of the common problems with this arrangement are complications related to the leads, including bleeding and infection. Rice’s prototype wireless pacemaker reduces these risks by doing away with leads.
Other recently introduced lead-less pacemakers also mitigate some of these complications, but their form factors limit them to a single heart chamber and they are unable to provide dual-chamber or biventricular pacing. In contrast, battery-less, lead-less and wirelessly powered microchips can be implanted directly to pace multiple points inside or outside the heart.
The chip at the system’s heart is less than 4 millimeters wide and incorporates the receiving antenna, an AC-to-DC rectifier, a power management unit and a pacing activation signal. A capacitor and switch join the chip on a circuit board that is smaller than a dime. The chip receives power using microwaves microwaves in the 8 to 10 GHz electromagnetic frequency spectrum.
The frequency of the pacing signals produced by the pacemaker can be adjusted by increasing or decreasing power transmitted to the receiving antenna, which stores it until it reaches a predetermined threshold. At that point, it releases the electrical charge to the heart and begins to fill again.
The team successfully tested the device in a pig and demonstrated it could tune the animal’s heart rate from 100 to 172 beats per minute.