Lawrence, Mass. ? For centuries, winter coats have worked on a pretty straightforward premise: trap the heat the body generates.

Unfortunately, that’s not quite suitable for the extreme cold that soldiers and outdoor enthusiasts often must endure for extended periods.

The solution: a new generation of high-tech jackets that create their own warmth, powered by lightweight lithium batteries.

The jackets jettison the electric blanket model  traditional wires running through cloth to produce heat. Instead, they conduct heat through stainless steel microfibers thinner than a human hair. The fibers are as washable, bendable and soft as the fabric into which they’re woven.

Malden Mills of Lawrence, which makes Polartec fleeces, has licensed the technology to The North Face, which is using it for the high-end MET5 jacket, and to Lands’ End for a blanket.

The North Face jacket doesn’t look unusual. But its vest lining heats to 114 degrees on full power, doubling its warming effectiveness.

Down the road, the heat fibers could also relay data, turning clothing into truly wearable computers  something scientists have experimented with for years but haven’t perfected for widespread use.

Someday, the technology could even turn strangely back on itself: air-conditioned textiles to keep the users cool.

Until production costs fall, The North Face and Malden Mills say wired textiles are likely bound for a niche market. “Think about photographers, policemen, construction workers, the military,” said Malden Mills spokesman David Costello.

The jacket sold by The North Face has two settings: Medium heats the fabric around the chest area up to 108 degrees for five hours. High goes to 114 degrees for 2 1/2 hours.

“It’s on your chest because you want to heat up the core where the heart and lungs are,” said Costello, who spent several 85-degree August days testing the technology in a frozen Massachusetts fish locker. “If the core is warm, where all the blood circulates through, then your extremities are fine.”

The North Face has done its own testing, sending teams of climbers and extreme athletes on wilderness expeditions.

The company even dropped one climber in a 20-foot crevasse and buried him in snow until he started shaking, then had him flip on the jacket.

“Soon afterwards he stopped shaking, and we realized this was a pretty cool project,” said Thomas Laakso, advanced project manager at The North Face, the San Leandro, Calif.-based unit of VF Corp.

A new version and a vest will be out in the fall.

The company claims MET5  with a $500 price tag  has been a big hit during limited release, though it declined to provide sales figures.