Tongue Display Unit research. Researcher (Yohan Payan) designing a set of pressure sensors to be used in a shoe with a Tongue Display Unit (TDU). The TDU, first developed in 1999, stimulates the tongue with input from an external sensor, and is an example of a tactile vision subsitution device. This shoe is designed to be used by an amputee. A wireless TDU in the patient's mouth will stimulate the tongue with information received from the pressure sensors in the shoes, triggered by the ends of the amputated limbs (here, the feet). This sensory input helps the amputee to keep his balance and avoid falling over. TDUs can also be used by paraplegics, surgeons, and blind people. Photographed in the TIMC-IMAG Laboratory in La Tronche, France.