This image illustrates the basic concept of North Carolina State University's envisioned hydraulic and latching polyvinylidene fluoride (PVDF) Braille dot. Four bending "bimorph" actuators are attached to a fluid-filled cavity. Voltage is applied to the two "hydraulic" bimorphs forcing them to bend inwards through windows in the cavity. As they bend they compress the cavity and the squeeze the hydraulic fluid up, lifting the Braille rod out of the cavity (depicted by the case on the right).
© NORTH CAROLINA STATE UNIVERSITY
The Web's wealth of information would lose some of its luster if you read it only one line at a time. Yet this is exactly how blind and other vision-impaired people today must experience the Web when they use electronic Braille displays connected to their computers. Braille displays use electromechanically controlled pins, as opposed to the lights in a conventional computer monitor, to convey information. Here is how: Software gathers a Web page's content from the computer's operating system, converts the words and images into a digital version of Braille and then represents that via a touchable row of finger-sized rectangular cells lined up side by side like dominoes. Each cell has six or eight small holes through which rounded pins can extend and retract with the help of piezoelectric ceramic actuators to represent various Braille characters. Each time a person reads the row of Braille with his fingers (left to right), the pin configurations refresh to represent the next line of a Web page's text, and so on.
Breaking Braille barriers
Efforts to improve Web pages translated into Braille have progressed slowly because of the cost and complexity of Braille displays, but a team of North Carolina State University researchers in Raleigh has taken the first steps toward developing a device that would allow the blind to take better advantage of the Web and other computer applications. Instead of presenting electronic content one line at a time, this display would translate words and images into tactile displays consisting of up to 25 rows, each with 40 cells side by side. Braille readers would have multiple lines of text and numbers at their fingertips, enabling them to backtrack and review content more easily. Another possibility might be to present in Braille equations and other information that take up more than one line at a time.
"It's difficult to achieve any spatial recognition with just a single line," says Neil Di Spigna, a research assistant professor in N.C. State's Department of Electrical and Computer Engineering who is working on the project.
The use of piezoelectric ceramic to make a Braille display with multiple rows would make already pricey displays even more expensive—low-end models with a single row already cost upwards of $1,000. In addition, the amount of energy needed to power multiple rows would make these displays bigger, heavier and less portable.
Touch and go
The N.C. State researchers are experimenting with two different approaches they hope will cut the costs and energy requirements of Braille displays in the future, and presented their latest research at the International Conference on Electroactive Polymer Actuators and Devices in San Diego last month.
The first approach would rely on hydraulic pressure to raise and lower each of the pins in a cell. In this scenario, each pin would sit in a fluid-filled plastic case. A window would be cut into the case and covered with a polyvinylidene fluoride (PVDF) film. When electricity is applied to the cell the PVDF would bend in and squeeze the case through that window, raising the level of the fluid and the pin along with it. The researchers say they have demonstrated a proof-of-concept prototype that, when less than 1,000 volts were applied, got the case to contract and push a fluid consisting of deionized water and food dye up so that a pin would rise more than 0.5 millimeters—the standard height of a Braille dot—in less than 100 milliseconds (initial experiments have been done without a pin in the case).