There's also a tongue display unit, which consists of a matrix you place on the tongue and it outputs DC voltages on the tongue. "The tongue display unit (TDU)

There's also a tongue display unit, which consists of a matrix you place on the tongue and it outputs DC voltages on the tongue. "The tongue display unit (TDU) for electrotactile spatiotemporal pattern presentation" - https://core.ac.uk/download/pdf/82729288.pdf https://core.ac.uk/download/pdf/82729288.pdf Also see - https://www.newyorker.com/magazine/2017/05/15/seeing-with-your-tongue https://www.newyorker.com/magazine/2017/05/15/seeing-with-yo...