A proposed active tactile display device would present textual and graphical information to a blind person. The concept of this device is a byproduct of recent research on the use of electroactive polymers to generate forces and displacements in novel robotic actuators.

Reading Pins Would Be Pulled Down Selectively by electrostriction in the silicone film at intersections between selected row and column electrodes to which a voltage would be applied.

The display medium would be a planar array of small cones called "reading pins" (see figure). Under computer control, reading pins would be lowered individually or in groups to produce a tactile pattern of highs and lows representing the information to be read. A person would read the pattern by scanning with fingertips, as in reading conventional Braille print.

The pins would be lowered by use of an electroactive polymer; specifically, a silicone that, in film form, has been found to contract by as much as 30 percent when subjected to an electric field. The reading pins would be mounted on an electrically insulating rubbery film on top of a silicone film on top of a rigid, highly electrically resistive substrate.

A given reading pin would be lowered by applying a voltage across the thickness of the silicone film at the location directly under the pin. Electrodes to apply voltages at such locations would be formed on the top and bottom surfaces of the silicone film. The electrodes on each surface would be evenly spaced, parallel metal film strips, and the top and bottom electrode arrays would be crossed to obtain a square grid corresponding to the locations of pins to be lowered. The electrode films would be formed before assembling the layers by sputtering, onto the substrate and onto the rubbery sheet, a layer of chromium 50 Å thick followed by a gold layer 1,500 to 2,500 Å thick. The electrode films would be formed into the required patterns by photolithography or ink printing techniques.

Because the actuated pins would be pulled down, the information to be displayed would have to be formatted analogously to an image on negative film; for example, ridges representing lines in an image would be formed by pulling down pins to form valleys between the ridges. The resolution of the display could be selected by choosing the pixel widths of letters, numbers, and other characters.

This work was done by Yoseph Bar-Cohen of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp  under the Electronics & Computers category.


This Brief includes a Technical Support Package (TSP).
Active Tactile Display Device for Reading by a Blind Person

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This article first appeared in the February, 2001 issue of NASA Tech Briefs Magazine.

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