Smart phones

More than half of all Americans carry 1 . Smartwatches and 2 may not be far behind. What's not all that smart are the rigid 3 that power our gadgets. But some may soon be replaced by ultra-thin, flexible batteries, sewn right into your clothes.Researchers built a prototype out of conductive, nickel-coated 4 fabric. They applied lithium compounds to create the anode and cathode, and separated them with a spandex-like material. The 5 battery was just half a millimeter thick, with a capacity of 510 milliampere-hours per cubic inch—about a quarter that of the battery in an iPhone 5. And the tighter the knit, the higher the capacity.Of course, fabric 6 . But this battery can too. Even after being folded 5,500 times, the battery kept trucking. Thin foil batteries, on the other hand, took just 70 folds to become really foiled. The findings appear in the journal Nano Letters.You don't even have to disrobe to charge this 7 battery. Researchers tacked flexible solar cells to it, so it can charge on the go. Might be just the thing to make polyester current again.