The Ink-free caught my eye. I would like to be available something like yesterday's `dirty dot' 9-pin dot matrix printer
with a stout solenoid print head gun to impact tactile enough like Braille pages for the blind, but alphanumeric. Has this happened, still available?
The chemistry behind the printing process is pretty amazing. It was invented by some ex-Polaroid people. It has a very powerful drawing program embedded in it, or running on a smartphone for the headless version.
Is it similar to thermal printing or something different?
It is color thermal printing. The chemicals in the paper have a phase transition that reveals the colors. That means you can heat them at different temperatures and durations to make the phase transitions happen selectively. Much easier said than done.