Some parts of our body tend to be more sensitive than others to the ambient temperature, and these spots supposedly have a great deal to do with how hot or cold we feel. At MIT’s Making And Designing Materials Engineering Competition (MADMEC), a contest between the institute’s engineering students, the winning entry was a device that straps around the arm to cool or heat the inside of the wrist and tweaks how the person feels.
The Wristify device has a heat sensor to detect the temperature of the skin as well as one for the air around the wrist. By constantly sensing and adjusting the temperature of the plate, the device may be able to help people stay comfortable throughout the day, even while moving around and changing their environment.
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. This 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.