Actually, what Arthur Clarke said was “any sufficiently advanced technology is indistinguishable from magic,” but that wouldn’t fit in a title, and it’s true either way. Paper batteries. Whoda thunk it. (Hat tip to Space Cowboy [1] for giving me the idea of blogging this.)
Seriously. Paper batteries. Actually, what they mean is carbon nanotubes arranged in a sheet of paper which acts as a battery when placed in the right sort of liquid.
A battery is just a way of having a source of electrons, moving those electrons from point A (the electron donor) to point B (the electron acceptor) and tapping into that flow to get electrical energy. In traditional batteries, that requires all kinds of parts, which corrode, explode, and generally die inconveniently.
A group of researchers at Rensselaer Polytechical Institute [2] have made the leap from many parts to an integrated battery. They use the analogy of vacuum tubes versus transistors, and that’s a pretty good one.
What allows them to do this is the amazing properties of nanotubes. Wikipedia [3] (which is a great resource so long as the topic is beyond Fox News [4]) explains that the electrical properties of nanotubes vary depending on how they’re “rolled.” Oversimplifying grossly, if the cylinder is formed by rolling “straight across,” the nanotube will act as a semiconductor. If it’s rolled “on the bias,” the nanotube will conduct electricity. Theoretically it can do so as much as 1000 times better than silver, which is one of the best conductors known.
The RPI group has imbued paper with aligned carbon nanotubes which act as electrodes on a battery when they’re in a solution that can conduct electrons. Water with dissolved salts can do that. Blood is essentially water with dissolved salts (and lots of other stuff). So, besides the fact that there are plenty of electronic and industrial applications where it would be convenient to have thin batteries you can twist into any shape, people are also excited about the medical applications. Neither paper nor carbon is toxic, and blood or intercellular fluid is a ready-made ionic solution, making these batteries a vast improvement over what’s currently available for pacemakers and the like.
There are, however, lots of things the press release glosses over. Batteries need a source of electrons. That’s what the lead acid, sulfuric acid, or lithium ions provide in a normal battery. Inside the body, you can probably keep pulling electrons out of the blood. In an electronic application, it sounds like you’d have to replenish the salt solution as the electrons get depleted. That may be no big deal, but they don’t actually say how this part is going to work.
Another thing that’s unclear is how the flow of electrons will be tapped. Where do you attach the wires? Maybe I’m missing something, or maybe it’s also no big deal, but they don’t say.
Frustratingly, all we have right now are press releases. The actual article is supposed to appear August 13th in the Proceedings of the National Academy of Sciences, but last I checked it hadn’t shown up yet. When it does, only the abstract may be available. Keep an eye on on the PNAS site [5] and if we’re lucky, the questions will be answered in the fullness of time.