This clock works by using a thermochromic foil based on liquid crystals that changes color with temperature. The foil is attached to a PCB with SMD resistors as heating segments.
At first, I tried to build a clock that was based on PCB heaters similar to my thermochromic temperature & humidity display. However, as the dimensions of the segments became smaller and therefore although their resistance, it was challenging to find proper drive electronics for so many channels that can supply enough current. Then the idea came to me to use SMD resistors instead.