This materials-driven study employs color-changing smart materials (specifically, thermochromic coatings) to develop a simple, straightforward means to vastly improve fire exit doors, which serve as an important means of egress in buildings.

Currently, fire exit doors do not provide any warning if there’s a fire on the other side of the door. People are told that, during a fire, they should travel to the exit door, and then either touch the door to see if it’s hot, or look through a small window in the door, if a window is provided (they usually aren’t).

Boooooooo!!

If you hear a fire alarm, wouldn’t it be great to be able to quickly glance at an exit door, from a distance, and have it tell you that it’s holding back a hot mess, and that you should use a different means of egress instead? Yes! That would be great!

This project does just that, using a thermochromic leuco coating. When the door is at, or below, body temperature, the coating is opaque. This means that it looks like a regular painted door if it's at room temperature (or if it’s a hot day, or if you touch it). But if there’s a fire, then the door heats up and the warmed thermochromic coating turns transparent, revealing a warning sign that appears from beneath it.

Interestingly, one of the biggest challenges of this project was not finding the right material; it was finding an effective way to communicate danger. Several studies were created, each attempting to convey “stop” at a glance. Considerations included different languages for different people, window voids in doors, and large graphics that might work for some visually-impaired people. The approach is easy, fail-safe and inexpensive, and the outcomes led to another idea that focused on fire door stickers.