Thursday 12 January 2017

ASSAULT AND BATTERY

Dick Pountain/Idealog 263/07 June 2016 11:26

Batteries, doncha just hate them? For the ten thousandth time I forgot to plug in my phone last night so that when I grabbed it to go out it was dead as the proverbial and I had to leave it behind on charge. My HTC phone's battery will actually last over two days if I turn off various transceivers but life is too short to remember which ones. And phones are only the worst example, to the extent that I now find myself consciously trying to avoid buying any gadget that requires batteries. I do have self-winding wristwatches, but as a non-jogger I'm too sedentary to keep them wound and they sometimes stop at midnight on Sunday (tried to train myself to swing my arms more when out walking, to no effect). I don't care for smartwatches but I did recently go back to quartz with a Bauhaus-stylish Braun BN0024 (design by Dietrich Lubs) along with a whole card-full of those irritating button batteries bought off Amazon that may last out my remaining years.

It's not just personal gadgets that suffer from the inadequacy of present batteries: witness the nightmarish problems that airliner manufacturers have had in recent years with in-flight fires caused by the use of lithium-ion cells. It's all about energy density, as I wrote in another recent column (issue 260). We demand ever more power while away from home, and that means deploying batteries that rely on ever more energetic chemistries, which begin to approach the status of explosives. I'm sure it's not just me who feels a frisson of anxiety when I feel how hot my almost-discharged tablet sometimes becomes.

Wholly new battery technologies look likely in future, perhaps non-chemical ones that merely store power drawn from the mains into hyper-capacitors fabricated using graphenes. Energy is still energy, but such ideas raise the possibility of lowering energy *density* by spreading charge over larger volumes - for example by building the storage medium into the actual casing of a gadget using graphene/plastic composites. Or perhaps hyper-capacitors might constantly trickle-charge themselves on the move by combining kinetic, solar and induction sources.

As always Nature found its own solution to this problem, from which we may be able to learn something, and it turns out that distributing the load is indeed it. Nature had an unfair advantage in that its design and development department has employed every living creature that's ever existed, working on the task for around 4 billion years, but intriguingly that colossal effort came up with a single solution very early on that is still repeated almost everywhere: the mitochondrion.

Virtually all the cells of living things above the level of bacteria contain both a nucleus (the cell's database of DNA blueprints from which it reproduces and maintains itself) and a number of mitochondria, the cell's battery chargers which power all its processes by burning glucose to create (ATP) adenosine triphosphate, the cellular energy fuel. Mitochondria contain their own DNA, separate from that in the nucleus, leading evolutionary biologists to postulate that billions of years ago they were independent single-celled creatures who "came in from the cold" and became symbiotic components of all other cells. Some cells like red blood cells, simple containers for haemoglobin, contain no mitochondria while others, like liver cells which are chemical factories, contain thousands. Every cell is in effect its own battery, constantly recharged by consuming oxygen from the air you breath and glucose from the food you eat to drive these self-replicating chargers, the mitochondria.

So has Nature also solved the problems of limited battery lifespan and loss of efficiency (the "memory effect")? No it hasn't, which is why we all eventually die. However longevity research is quite as popular among the Silicon Valley billionaire digerati as are driverless cars and Mars colonies, and recent years have seen significant advances in our understanding of mitochondrial aging. Enzymes called sirtuins stimulate production of new mitochondria and maintain existing ones, while each cell's nucleus continually sends "watchdog" signals to its mitochondria to keep them switched on. The sirtuin SIRT1 is crucial to this signalling, and in turn requires NAD (nicotinamide adenine dinucleotide) for its effect, but NAD levels tend to fall with age. Many of the tricks shown to slow aging in lab animals - calorie-restricted diets, dietary components like resveratrol (red wine) and pterostilbene (blueberries) - may work by encouraging the production of more NAD.

Now imagine synthetic mitochondria, fabricated from silicon and graphene by nano-engineering, millions of them charging a hyper-capacitor shell by burning a hydrocarbon fuel with atmospheric oxygen. Yes, you'll simply use your phone to stir your tea, with at least one sugar. I await thanks from the sugar industry for this solution to its current travails...

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