Thermochromic (heat sensitive) protest banner. Custom milled PCB. Nichrome wire. Arduino Uno. 9V batteries. Scrap fabric. Paint. Made for the People's Climate March on April 29, 2017 in Chicago.
It is only operational between 60° F - 80° F. Due to inclement weather and temperature below the window of functionality (it was 43° F outside and the wire could not reach 92° F, the temperature at which the ink turns clear), the banner was solid blue for the duration of the march.