Electric socks thaw cold feet
Battery powered socks could help office-workers, hang-gliders and people who suffer from poor circulation to feel their toes in winter, researchers say.
The idea is that a person could switch on the socks, which contain conductive fibres, when they start to feel cold.
The hot sock has heating panels made from a blend of Australian Merino wool and a secret flexible, washable fibre that produces heat as it conducts electricity. Johnson won't say if the conductive fibre is metallic or a polymer.
People get cold feet if they can't produce enough heat to make up for heat lost through their feet. But the socks generate heat to counteract that.
"The rate of heat generated would equal the rate of heat lost," Johnson told ABC Science Online.
When feet get sweaty, this speeds up heat loss.
But woollen socks are good at absorbing moisture and thus are less likely to lead to heat loss. Woollen socks are also less likely to smell, are resilient and breathe well.
"Wool is an outstanding sock fibre," said Johnson. "What we're doing is adding some extra performance level to what is already a good sock."
Johnson said the product development team was dealing with the problem of electricity flow leaking away due to excessive moisture in the sock.
So, he said it would be important for the wearer to switch on the heater before the sock got too moist or the heating system would not be as efficient.
"It's not a problem safety-wise because we're looking at extremely low voltages and currents," he said. "It's just a matter of efficiency; the life of your battery would be reduced."
The present prototype sock uses a 7 volt battery that Johnson said could eventually be kept in a pouch knitted into the sock. The battery would last four to six hours and be rechargeable overnight.
"The socks will be available commercially first in the U.K. early next year but Johnson could not give an estimate of the cost.
Johnson said that the amount of electromagnetic radiation the socks gave off was "totally undetectable" and was not a safety concern.
"We're looking at microcurrents down very fine fibres so I don't think it's an issue."
Johnson said such conductive textile technology could even be used to build a wearable and versatile "Faraday cage", to protect people from electromagnetic radiation.
"We've considered applications, for example, with high voltage electricity line power workers who might want to wear that sort of protection," he said.
"People with heart pacemakers might want to wear a vest just to ensure there's no interference with the electronics of their pacemakers."
Johnson's team has also considered developing screens in hospitals and offices to protect sensitive equipment from atmospheric electromagnetic radiation.