South Korean scientists have developed a way to charge cell phones using the human voice by creating a flat material that generates electricity from sound waves. While not enough to fully charge a phone yet, the energy could power small devices like sensors. Researchers are working to improve the material to generate more power from lower sound levels. Separately, scientists at the Georgia Institute of Technology have created a chip that harnesses body movements to charge devices like iPads. While talking on phones drains batteries, this method may allow phones to charge as long as the user is speaking.