"New physics" brings an update to 40-year-old braille tech

Non-sighted computer users, on the whole, have not had access to the tremendous gains in computer interfacing that many of us have taken for granted.

Largely restricted to braille innovations developed and unchanged since the 1980s, non-sighted computer users have not seen braille technology scale in the same way that sighted technology has. Between expensive displays and exponentially complex designs, the technology behind refreshable braille displays is long overdue for an upgrade.

And thanks to a newly discovered physical property of polymers, a team of engineers from the California Institute of Technology (CalTech) might just have the answer.

"We should be able to really push the limits of the density of [information]."

Traditional refreshable braille displays use the piezoelectric effect which works by using voltage to expand small crystals attached to a single braille dot in the display. As the crystal expands due to the voltage, the small dot raises for the user to interact with. It can take as many as eight dots to create a single letter using this display.

While this approach may seem straight forward, coauthor of the research poster and graduate researcher at CalTech, Rob Learsch, tells Inverse that the complexity of this approach scales exponentially as the crystals are used to express more information. As a result, these types of refreshable displays are limited in the number of characters they can express at once.

Instead, the approach that Learsch and his team developed, which was presented last week on the American Chemical Society's digital SciMeetings platform, describes an entirely new approach to manipulating traditional polymers used in braille technology.

"[This] represents a new type of physics that we haven't seen represented anywhere else," says Learsch. "Which is very exciting."

The team's approach works by using a new form of electroactive polymers (EAPs) in place of the traditional crystal. These EAPs contain a tangle of both positively and negatively charged polymers that when activated using an electric field separate and spring back like cut rubber bands. This reaction causes the material to expand and push-up dots in the braille display.

Learsch tells Inverse that these EAPs require thousands of times less energy to operate than traditional braille displays which makes them easier to build and scale. This could lead to the creation of higher resolution devices that can display more complex information like charts and graphs to users.

"Something that's very, very interesting to me is that [with this technology] we should be able to really push the limits of the density of [information]," says Learsch. "If you imagine [this information] as pixels, in a typical braille character or braille display there's not many pixels per inch. But there's no good reason that we couldn't have them as dense as video pixels on a TV or iPhone. So it's interesting to see how densely we can put them together and how well we can control the degree of [polymer] swelling."

Additionally, because this material can also act as a capacitor by translating pressure into an electric signal, Learsch says its a good candidate material for designing braille-friendly touchscreen devices as well.

And even beyond braille technology, Learsch tells Inverse he's excited for the future engineering possibilities of this new material as well, including robotic joints and grippers.

"Using this to produce refreshable braille displays is just the beginning," says Learsch. "A polymer material that can change shape in a controlled and programmable way could be used as one-way valves, used in grippers or joints, or an incredible amount of other applications."

Abstract: Development for refreshable braille devices has recently shifted to electroactive polymers (EAP). This paradigm benefits from greater precision, smaller size, and lower cost associated with modern electronics, opening the door for higher resolution and less expensive devices. Displays with resolution finer than required to display braille characters will enable representation of non-text information such as figures, tables, or diagrams. However, adoption of EAPs for responsive displays has encountered problems such as high required field strength (kV/cm), insufficient pressure (2 kPa generated), and poor durability. This work presents a new type of electroactive polymers, based on poly ionic complexes. In contrast to previously reported electroactive polymers, these gels do not rely on a solvent bath, respond to a field that is on the order of V/cm, and expand in a direction parallel to the applied electric field. Ultimately, the expansion is driven by electrostatic interactions: The polyionic gels are overall charge neutral, however, when an electric field of sufficient strength is applied, the ionic bonds are broken and the polycation is drawn towards the plate. This reveals the charged backbone of both the polyanions and the polycations, which causes the repeat units to repel one another and the gel to expand. This mechanism is confirmed using cyclic voltammetry and impedance spectroscopy. With the understanding of the mechanism, the gels are made to expand rapidly and tolerate 100s of cycles. These properties are controlled through the identity of the ionic repeat units and further tuning the crosslinking and processing of the gels. The ionic crosslinks within the gel impart desirable qualities such as self-healing and high toughness a through a cooperative effect, yielding durable gels that are the much stronger than their component parts.The low power requirements and resilient nature of these EAPs make them attractive for use as refreshable braille displays. This methodology could be adapted to other actuators such as soft robotic joints or grippers.