U.S. engineers say they\'ve developed a micro fuel cell that could be a low-cost, eco-friendly power source for devices like tablet computers and smartphones. Researchers at Yale University report their tiny power sources are made of materials known as bulk metallic glasses, pliable yet more durable than the metals typically used in micro fuel cells. A fuel cell, as an alternative to a battery, is an electrochemical device that combines hydrogen and oxygen to produce energy, giving off only water and heat as byproducts. In the Yale fuel cells, the metallic glasses are finely shaped and molded using an efficient and inexpensive fabrication process similar to processes used in shaping plastics, the researchers said. \"These amorphous metal alloys are amazing materials that can be easily shaped into both large and small nanostructures, yet retain suitable properties for a wide range of electrochemical applications,\" chemical and environmental Professor Andre D. Taylor said. The alloys have randomly arranged atoms rather than the orderly crystalline makeup of ordinary metals, researchers said. The result, they say, is a tough but elastic substance as strong as steel yet malleable and good at conducting electricity. The researchers have demonstrated their fuel cell -- measuring just 3 cubic centimeters and based on zirconium and platinum compounds -- generates power and said they are now working to increase its output.