Currently, visually impaired people use Braille displays equipped with piezoelectric actuators, which are costly and bulky. The major challenge in designing a more suitable Braille device lies in the integration of a large number of milimeter-scale actuators. As part of the Ability project, we are focusing on developing a 2D Braille display that innovates by replacing piezoelectric actuators with a novel technology to active the pins. However, numerous reserchers are exploring different technologies to make Braille displays accessible to a wider audience.
A recent article introduces a new technology using a poly(N-isopropylacrylamide)(PNIPAM) thermosensitive gel as a flexible actuator. Macroporosity is introduced into the gel, accelerating the response time from several hours to a few seconds. At temperature above 34°C, PNIMAM undergoes reversible contraction with a significant swelling ratio up to 1000%. This volume change is attributed to a modification in PNIPAM solubility, leading to water transfer into/out the polymer matrix and a slow response to stimuli. The authors combined two recent developments to overcome these limitations. The first is the synthesis of a mechanically robust hydrogel, and the second is the synthesis of a fast-reacting gel with a macroporous structure. Combining these scientific advances results in an intelligent gel suitable for flexible actuation.
To demonstrate the capabilities of the new actuation technology, a one-pin Braille prototype was constructed. It consists of a central part with a 3D-printed containment unit for the gel and water, and a small rod placed above that can move vertically through a hole. An electrolysis device (placed under the gel) and a nichrome wire (wrapped around the gel) were used to cool and heat the system, respectively. The initial results are promising, as the prototype effectively lifted a pin. Further work is planned to develop a prototype with a set of 8 pins to display letters and even images.
(Left Image representing the principle of the thermosensitive PNIPAM gel, and right image representing the pin activation, with its different parts).
Article: https://pubs.acs.org/doi/epdf/10.1021/acsami.2c17835 (images from the article)