Wristify operates on the concept that exposing just one small area of skin to a quick temperature change can affect the wearer's thermal comfort by changing the person's perception of temperature. Place a cold washcloth on your forehead and you immediately feel cooler, but eventually your body adapts to the temperature change so that it no longer perceives the washcloth as cold. Wristify is designed to make the wearer continue to feel cool by sending a steady stream of increasingly colder pulses to the skin [sources: Vanhemert, Burlingame].
The product's developers say it takes a temperature change of more than 0.1 degrees Celsius (0.18 degrees Fahrenheit) per second in order to make a person feel several degrees warmer or colder. A current Wristify prototype changes at 0.4 degrees per second and works for up to eight hours a day on a lithium battery. That was good enough to earn it a $10,000 first place prize at an MIT materials-science design competition in October 2013 [sources: Matheson, Burlingame].
The prototype looks like a man's watch. It includes a square face component called a thermoelectric heat sink that's composed of copper alloys and lowers the device's temperature by dissipating heat. The gadget, worn with a wristband, also includes thermometers that measure body and air temperatures and an automated operation system to control the intensity and duration of pulses. Because the technology is intended to change the wearer's perception of temperature, Wristify doesn't allow the wearer to adjust the temperature manually. The prototype currently comes attached to a number of unsightly wires, but developers say they are working to make the device better-looking and easier to wear [sources: Burlingame, Matheson, Wristify].
Can't wait to wrap one of these around your wrist? The product isn't commercially available just yet, but experts and energy conservationists are already getting excited about its potential impact.