Improving tactile communication

A scientist at NASA has proposed an active tactile display device that would present textual and graphical information to a visually impaired person.

The concept of this device, developed by Yoseph Bar-Cohen of Caltech for NASA’s Jet Propulsion Laboratory, is said to be a by-product of recent research on the use of electroactive polymers to generate forces and displacements in robotic actuators.

The display medium would be a planar array of small cones called ‘reading pins’. 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.

Bar-Cohen proposes that 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 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 Ã… thick followed by a gold layer 1,500 to 2,500 Ã… thick.

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. Pulling down pins and forming valleys between the ridges would form ridges representing lines in an image. The resolution of the display could then be selected by choosing the pixel widths of letters, numbers, and other characters.

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