Hungry Batteries concept slim down as they get drained

Designer Mac Funamizu has come up with a rather strange concept – the Hungry Batteries that will come in a traditional form factor, although they will physically end up slimmer and slimmer the less charge they hold. Basically, this is a visual aid that indicates it is time for a recharge, although we think it might be cheaper to just include one of those strips that can tell how much juice there is left within when pressed on both ends with your thumb and forefinger. No idea on what kind of material would be suitable to make this concept a reality, but perhaps a form of smart sponge will do’?