Not all tattoos are purely visual. Some of them – so-called “Braille tattoos” – have another dimension (literally) that allows people who understand Braille to touch them and read them in a purely tactile way. I’ve seen a couple of dozen Braille tattoos in my life. About half of them were conceptual, but the rest were functional and readable.

If you want a conceptual ‘Braille tattoo’ then a simple ink tattoo will be fine. Someone who understands Braille will be able to ‘read’ the dots, but only visually. A blind person won't be able to read them though as although there is some minimal scarring from a normal ink tattoo, it’s almost imperceptible to touch.