For fifty years, scientists have been trying to create tiny gadgets that travel around a patient’s bloodstream, detecting and even fixing diseases. But how to power them has been a problem. Formerly-used batteries have shrunk over the years but have not been miniaturized sufficiently to fit into a medical device small enough to travel through veins and arteries. So instead of using them, engineers at Stanford University have developed tiny implants that can be powered by radio waves beamed from a transmitter outside the body. The idea of using electromagnetic waves to transfer power to implantable medical devices is not new, and in principle, it sounds simple. A transmitter outside the body emits radio waves travelling through the tissues. They are then picked up by an antenna on the internal device where they induce a voltage. The trouble is, scientists previously thought that radio waves would struggle to get through human tissue. But a researcher at Stanford University found strong evidence that they do pass through. He used a chunk of beef as a stand-in for human flesh and found that sufficient energy moved through it to make electromagnetic power transfer feasible. Already, working prototypes that can propel themselves have been developed, but the distance through which power can be transferred inside the body still needs improvement.