This work was sponsored by Robert Draper Technology Innovation Fund, sponsor numbers 981517 and 991000, UW Innovation & Economic Development Research Fund, and the Charles E. Culpeper Foundation (absorbed by Goldman Philanthropic Enterprises, then by Partnership for Cures). The project dates were 1/14/1998–6/30/1998, 7/1/1998–6/30/1999, and 4/14/1998–4/13/1999. The research was conducted at the University of Wisconsin–Madison, and the principal investigator was Kurt Kaczmarek in collaboration with Mitchell Tyler and Paul Bach-y-Rita.
The Tongue Display Unit (TDU), version 1, is a portable, battery-powered device that in a stand-alone mode can display static 12 X 12 tactile pattterns on the tongue. By connecting this device to a computer via RS-232 serial link, a custom command language can create real-time controllable tactile images on the tongue.
The tongue array is built on a flexible printed circuit substrate. Electrode spacing and size are adjustable depending on application. The photo below shows a 144-pixel array. The electrodes shown have a diameter of 2.13 mm and are placed in a square grid on 2.34-mm centers. Recent research has shown that somewhat smaller electrodes (1.55 mm diam.) produce a sensation with an acceptable perceived stimulation quality. The electrode arrays were manufactured by a commercial flexible circuits vendor, All-Flex Inc.
It is not well-known that the TDU was based on a earlier (1997) device specifically designed to stimulate the tongue, shown below. We call it TDU version 0, shown below. The circuit is a modified version of the circuit used for our 24x24 fingertip tactile display.
This device was used to perform research to determine the best electrode geometry and intensity control method: K. A. Kaczmarek and M. E. Tyler, Effect of electrode geometry and intensity control method on comfort of electrotactile stimulation on the tongue, Proc. ASME Dyn. Sys. Contr. Div., Orlando, Florida, pp. 1239-1243, 2000.
A full technical description of the TDU appears at: Kaczmarek, K.A. (2011). The tongue display unit for electrotactile spatiotemporal pattern presentation. Scientia Iranica D. 18, 1476-1485. doi:10.1016/j.scient.2011.08.020