I've always been told that battery technology is the bottleneck. Until we can figure out how to push more power in smaller spaces, it will be hard to evolve portable devices to the next level. As an example, just look at all the constraints smart watch makers are facing with the amount of screen time they can be turned on and the problems with charging your watch. A team at Stanford seems to have made a breakthrough with better materials. The whole thing feels pretty science fiction to me using elements with "infinite" growth and tiny nanosphere cages to hold things together. Nevertheless, it sure would be nice if I could get a week out of a phone charge instead of a day. Do you think our kids will bore their children with stories of having to charge their phones the way we bore our children with stories of rotary dials?