Implantable medical devices in the human body have revolutionized medicine. Hundreds of thousands if not millions of pacemakers, cochlear implants and drug pumps are today helping patients live relatively normal lives, but these devices are not without engineering challenges. irst, they require power, which means batteries, and batteries are bulky. In a device like a pacemaker, the battery alone accounts for as much as half the volume of the device. Second, batteries have finite lives. New surgery is needed when they wane.
Stanford electrical engineers have now developed a super-small, implantable cardiac device that gets its power not from batteries but from radio waves transmitted from a small power device on the surface of the body. The implanted device is contained in a cube just 0.8 millimeter on a side. It could fit on the head of pin. The findings, say the researchers, could dramatically alter the scale of medical devices implanted in the human body. The engineers say the research is a major step toward a day when all implants are driven wirelessly. Beyond the heart, they believe such devices might include swallowable endoscopes – so-called "pillcams" that travel the digestive tract – permanent pacemakers and precision brain stimulators – virtually any medical applications where device size and power matter.
"Wireless power solves both challenges," said Ada Poon, assistant professor of electrical engineering, who headed up the research. She was assisted by Sanghoek Kim and John Ho, both doctoral candidates in her lab. Last year, Poon made headlines when she demonstrated a wirelessly powered, self-propelled device capable of swimming through the bloodstream. To get there she needed to overturn some long-held assumptions about delivery of wireless power through the human body.