One challenge for medical devices that are implanted within the body — such as pacemakers, drug pumps or neural stimulators — is power. Generally, they're powered by batteries, but when the power runs out, the batteries have to be replaced, requiring further invasive surgery. Professor John Rogers, from the Department of Materials Science and Engineering at the University of Illinois at Urbana-Champaign, has developed a device that can generate electricity from the movement of organs within the body. His device uses a piezo-electric material that produces electricity when bent. When attached to a beating heart, it produces enough electricity to run a pacemaker or other device, while apparently having no impact on the heart's function.