Mark Harris

Plug into an orange?
Juiced up gadgets are go! Mark Harris uncovers the energy hidden inside your daily grub

When your phone runs out of juice halfway through a call, the last thing you’d do is dunk it in a glass of OJ for real. But if scientists have their way, we could soon be dribbling drinks into our iPods, whipping up an omelette for an exhausted laptop or giving our last Rolo to help a digital camera back on its feet.

Food-powered gadgets are nothing new – you can already buy (or even make) a digital clock that uses the natural acidity of lemons or oranges to generate a weak electric current. But even a smoothie bar full of citrus fruit would struggle to drive one of today’s high tech smart phones.

So researchers are turning to microbial fuel cells (MFCs) to create sustainable, non-polluting power sources. Inside the MFCs live a colony of tiny bacteria - ironically even the E. coli bugs that can cause food poisoning in humans. These bacteria are fed food which they oxidise to create a flow of current. Although most MFCs use high energy rations like pure sugar, there’s no reason why future devices couldn’t eat exactly what’s on our plates or even filter tiny scraps of organic material from waste water.

The advantages of MFCs are numerous: they don’t squander dwindling fossil fuels, they aren’t made from polluting heavy metals (like today’s batteries) and they produce virtually no emissions. MFCs are also theoretically much more efficient than normal petrol engines.

Scientists at the University of the West of England are working on EcoBot-III, an independent robot that can search out its own food, process it into electricity using MFCs and then excrete any leftover material. The current version doesn’t even need tasty sweets to work – it can run on simple domestic sewage. The only drawback is that MFCs currently produce just a trickle of electricity compared to traditional electric batteries.

The university’s Dr Ioannis Ieropoulos says, “A single MFC is no match for a standard AA alkaline battery. In fact, it generates about four hundred times less energy for its size. But the important difference is that an MFC can provide a continuous energy supply for as long as the bacteria are kept alive. Potentially, this could be years, where there’s continuous inflow of key ingredients (in this case, sewage) and continuous outflow of waste products.”

This means that the first practical uses of MFCs are likely to be in tiny devices, powering pacemakers and medical sensors inside our bodies, where they can harvest all the organic ‘food’ they need from our bloodstream.

Scientists wanting more power could always turn to the Americans for help. Researchers at the University of Texas at Dallas have made artificial muscles that are 100 times stronger than nature can manage. These cyber-muscles use chemical rather than biological reactions, with nano-engineered carbon tubes using alcohol to contract metal ‘muscle’ wire.

The artificial muscles could be fitted into robots or humans, boosting strength and endurance and raising the possibility of the first completely artificial hearts. But whether we puny humans are ready for a future where super-strong, booze-powered robots compete for our dinner and deposit cyber-turds on our doorsteps is another thing entirely…

Countdown to health
There’s no getting away from today’s calorie counting gadgets – they can tell how much energy you’re expending while walking to work, listening to music or simply chatting on the phone.

Nokia 5500 Sports £200 pay as you go, or from free with contract
Super-tough sports phone with a built-in motion sensor. Can also schedule training sessions and read texts out loud while you’re jogging.

Polar F6 Heart Rate Monitor £70
Strap the watch to your wrist and the monitor to your chest for pin-point readouts of your heart rate and calories burned.

Tanita PD-637 Pedometer £15
This bleeping pedometer will either encourage you to exercise that little bit harder each session - or quickly drive you insane.

Sony Sports Walkman NW-S203 £80
If someone else in the gym has the beeping Tanita (above), you’ll be glad you’ve got this shockproof calorie-counting MP3 player plugged in to your lugholes.

  Return to Metro journalism page