Battery life remains a major concern for popular mp3 players and cell phones that are required to perform an ever-expanding array of functions. But beyond mere consumer convenience, a new advance in piezoelectrics may lead to self-powering cell phones and other electronic devices that can convert sound waves produced by the user into the energy it needs to keep running. Cagin and his partners from the University of Houston have found that a certain type of piezoelectric material can covert energy at a 100 percent increase when manufactured at a very small size – in this case, around 21 nanometers in thickness. Piezoelectrics are materials (usually crystals or ceramics) that generate voltage when a form of mechanical stress is applied. Conversely, they demonstrate a change in their physical properties when an electric field is applied and piezoelectric matrials work at the nanoscale between 20 and 23 nanometers and improve the energy-harvesting capacity by 100 percent.