Most bracelets aren't likely to alter your temperature too much either way, but the Wristify isn't most bracelets. Developed by four MIT engineering students, the Wristify works on the principle that heating or cooling the skin on one part of the body can make the entire body feel warmer or colder. By creating a personal heating and cooling device, the Wristify team ultimately hopes to cut the amount of energy currently used to heat or cool entire buildings.

Currently at working prototype stage, the Wristify resembles a wristwatch with a custom copper-alloy-based heat sink. This is is attached to an automated control system that automatically adjusts the intensity and duration of thermal pulses that are delivered to the heat sink based on readings from thermometers integrated into the device that measure external and body temperature. The prototype can run for up to eight hours thanks to a lithium polymer battery.

While developing Wristify, the team found that minute, rapid changes in temperature on one part of the human body can affect the whole body. They discovered that a change of 0.1° C (0.18° F) a second is the minimum rate required to make the entire body feel several degrees warmer or colder. The current prototype, which is the team's 15th, is capable of a rate of change of up to 0.4° C (0.7° F) per second.

The team believes that by providing individuals with a personal cooling and heating device, the Wristify has the potential to cut the amount of energy currently used to cool and heat the space within buildings. They say that adjusting the temperature of just one building by 1° C (1.8° F) can consume around 100 kWh per month, so while the device won't be able to completely replace a building's heating and cooling system, it could allow for significant savings.

“Buildings right now use an incredible amount of energy just in space heating and cooling. In fact, all together this makes up 16.5 percent of all US primary energy consumption. We wanted to reduce that number, while maintaining individual thermal comfort,” says Sam Shames, who co-invented the Wristify with Mike Gibson, David Cohen-Tanugi, and Matt Smith. “We found the best way to do it was local heating and cooling of parts of the body.”

The team recently took out the US$10,000 first prize in MIT's annual Making And Designing Materials Engineering Competition (MADMEC). They plan to use the money to continue development of the device. This will include using more advanced algorithms to improve the automation of the thermal pulses.

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