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Now, bracelet that heats or cools your body in one switch

Last Updated: Sunday, October 27, 2013 - 21:50

Washington: MIT scientists have developed a novel thermoelectric bracelet that keeps tabs on air and skin temperature and allows you to control your body temperature.

 Heating or cooling certain parts of your body such as applying a warm towel to your forehead if you feel chilly can help maintain your perceived thermal comfort.

Using that concept, four Massachusetts Institute of Technology (MIT) engineering students developed a thermoelectric bracelet that monitors air and skin temperature, and sends tailored pulses of hot or cold waveforms to the wrist to help maintain thermal comfort.

 Although people would use the device for personal comfort, the team says the ultimate aim is to reduce the energy consumption of buildings, by cooling and heating the individual ? not the building.

 "Buildings right now use an incredible amount of energy just in space heating and cooling. In fact, all together this makes up 16.5 per cent of all US primary energy consumption. We wanted to reduce that number, while maintaining individual thermal comfort," said Sam Shames, a materials science and engineering senior who co-invented the Wristify technology.

 The team estimates that if the device stops one building from adjusting its temperature by even just 1 degree Celsius, it will save roughly 100 kilowatt-hours per month.

 Over the course of developing its technology, the Wristify team made a key discovery: Human skin is very sensitive to minute, rapid changes in temperature, which affect the whole body.

 They found they needed to heat or cool any body part (in their case, the wrist) at a rate of at least 0.1 C per second in order to make the entire body, overall, feel several degrees warmer or colder.

 After 15 prototypes, the team landed on its final product, which resembles a wristwatch and can be powered, for up to eight hours, by a lithium polymer battery. The prototype demonstrated a rate of change of up to 0.4 C per second.

 The "watch" part of the prototype actually consists of the team's custom copper-alloy-based heat sink  - a component that lowers a device's temperature by dissipating heat.

 Attached is an automated control system that manages the intensity and duration of the thermal pulses delivered to the heat sink. Integrated thermometers also measure external and body temperature to adjust accordingly.

 "What we developed is a wearable, wrist-based technology that leverages human sensitivity, can detect and perfect rates of change, and can maintain overall thermal comfort while reducing the need to heat and cool buildings," Shames said.

First Published: Sunday, October 27, 2013 - 21:50
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