Who’s going to need a jet engine in his pocket? You will, so all the wireless gadgets you’re likely to carry around in the future can keep going strong. Portability is a virtue but also a curse: even a Wi-Fi-capable laptop needs to be plugged in frequently to recharge. “People want longer run times, and the only way to do that right now is with bigger batteries,” says James Balcom, CEO of fuel-cell firm Polyfuel in Mountain View, California. Researchers are developing power sources that are as small as the gadgets they’re meant to drive, shrinking everything from jet engines to nuclear-power plants down to the size of silicon chips in the search for the perfect battery.
The first crop of such devices may hit the market next year. At the front of the pack are micro fuel cells, tiny versions of the hydrogen-fueled power plants often touted as the key to the automobile’s future. A fuel cell is something like a battery that runs on replaceable fuel, typically taking in hydrogen and sending it through a membrane that screens out electrons, forcing them into a circuit where they can do electrical work. Now, thanks to micro-manufacturing techniques, 50 or so companies are working on fuel cells as small as matchboxes that might power a portable device for a day or more.
One of those companies is Medis Technologies, an Israeli firm that next year plans to introduce a 200-gram, $15 fuel cell capable of recharging a cell phone or digital camera up to five times on a ration of fuel. The first version will be disposable, but others will accept a $2.50 refill cartridge. “It will be like walking around with a wall outlet, except it’s smaller than a fist and weighs almost nothing,” says Medis CEO Robert Lifton.
As soon as next year fuel cells will come built into the lids or bases of laptop computers; Motorola, Samsung and Toshiba have demonstrated prototypes. Duracell and Bic are working on drop-in fuel cartridges that you’ll be able to buy like ordinary batteries. And fuel cells are likely to get a lot smaller yet, as researchers figure out how to put them on silicon chips. Developers are still wrestling with the excess heat and tiny trickles of water that most cells produce.
If a few drops of water seem inconvenient, picture a cell phone containing a jet engine spewing exhaust at 1,000 degrees Celsius. That’s Epstein’s plan–and it’s not farfetched. The MIT professor’s “micro gas turbine” is a bit like a two-centimeter-wide sealed window fan with two stacked blades inside the housing. The first blade, or turbine, compresses the inrushing fuel-and-air mixture for combustion, and the resulting explosion of hot gas turns the other blade, which drives a tiny electric generator. The 2-gram engine is expected to produce 20 watts of power with 16 grams of fuel per hour. “It has the potential to be the highest-efficiency, most compact form of portable power around,” says Epstein. Don’t worry about noise: the device shrieks at frequencies too high for humans to hear.
Speaking of things you’d hesitate to fire up in your trousers, how about a nuclear chip? Researchers Amit Lal of Cornell University and James Blanchard of the University of Wisconsin at Madison use a sort of microscopic seesaw to intercept the particles hurled from the atoms in radioactive nickel; the particles set the seesaw swinging, and that motion is converted into a billionth of a watt of electricity–enough to drive tiny embedded sensors that might warn of intruders in a maintenance tunnel or detect an epileptic seizure. In a few years, the tiny current would build up enough juice to fire off a cell phone call. That could make nuclear chips, which can last 100 years, the power of choice for emergency phones and other devices that might have to sit untended for a decade or more. Compared to using a nuclear phone the malodorous hiss of your jet-engine-powered cellphone may seem downright reassuring.
