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Braille displays could become more detailed and resilient with new material

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A new material has been developed that could improve refreshable braille displays that are currently only able to show a relatively small amount of information at one time.

Braille displays can translate information from the screen into raised characters, often along the bottom of a keyboard. However, this technology can cost thousands of dollars and is limited, typically displaying a string of characters much shorter than most sentences.

They currently rely on the piezoelectric effect, whereby a small crystal expands when voltage is applied to it, pushing a pin upward to create a dot. A single character, such as a letter, is encoded by up to eight such dots.

Devices on the market typically display 80 characters at most at one time - a fraction of a typical sentence or tweet.

Researchers have been looking at using electroactive polymers (EAPs) instead, as a type of material that could improve these displays. EAPs could display much more information than conventional devices, as well as a greater diversity.

The devices could also be easier and cheaper to manufacture, but until now they have encountered many issues, including the need for high voltage to operate and poor durability.

“With more development, we think this new material’s properties could make it possible to create much higher-resolution devices, perhaps even those capable of displaying information other than text, such as diagrams or maps,” said Julia R. Greer, principal investigator on the project.

Greer’s team at the California Institute of Technology (Caltech) conceived of an entirely new type of EAP based on polyionic complexes.

An improved EAP could help braille technology catch up to that used by those with sight, said researcher Rob Learsch.

“Braille technology hasn’t changed much since the 1980s,” he notes. “I think it would be remarkable to allow everyone to benefit from the revolution in miniaturisation and computation that has occurred.”

Whereas conventional EAPs rely on electrical charge accumulating on electrodes, the new material contains positively and negatively charged polymers combined into a random network of chains connected at nodes.

The negatively charged polymers form a solid scaffold to which the positive ones bind, acting like rubber bands that pull everything together.

Applying an electrical field unravels these connections, as if cutting the rubber bands, and causes the material to expand outward. The polyionic EAP requires much less voltage, and is more efficient and resilient, than conventional EAPs.

The researchers are now developing it to the point where it can be used within braille displays and potentially offer new functionality for these devices.

As the material can act like a capacitor, generating an electrical signal when pressure is applied, it could be used to build braille displays that respond to touch, much like the screen of a smartphone or tablet.

The material also could be used for other applications. If controlled by precise electrical fields, Learsch said he could foresee it opening and closing a robotic joint or gripper: “There is a lot of research to be done to get us from where we are now to these types of products, but that is all part of our long-term vision”.

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