Structures demonstrating the viability of both the hydraulic and latching Braille dot, and the dielectric elastomer fiber
Braille dot have been fabricated and characterized. A hydraulic proof-of-concept structure has achieved the necessary
volumetric change required to lift a Braille dot over 0.5mm at voltages under 1000V and at speeds under 100ms. Long
bimorphs have been fabricated that demonstrate large tip displacements over 2mm that could be used to mechanically
latch the Braille rod in the 'up' position to achieve the force requirement. The addition of radial prestrain in dielectric
elastomer tubes has reduced the wall thickness and directed the strain in the axial direction which has had a dramatic
impact on their resulting characteristics. The required bias voltage for the dielectric elastomer fiber Braille dot has been
reduced from 15.5kV to 8.75kV while the Braille head tip displacement of a fabricated prototype has almost tripled on
average and now also exceeds the required displacement for a refreshable Braille display. Finally, potential solutions to
the current shortcomings of both designs in meeting all of the requirements for such a display are discussed.
The development of a multiline, refreshable Braille display will assist with the full inclusion and integration of blind
people into society. The use of both polyvinylidene fluoride (PVDF) film planar bending mode actuators and silicone
dielectric elastomer cylindrical tube actuators have been investigated for their potential use in a Braille cell. A liftoff
process that allows for aggressive scaling of miniature bimorph actuators has been developed using standard
semiconductor lithography techniques. The PVDF bimorphs have been demonstrated to provide enough displacement to
raise a Braille dot using biases less than 1000V and operating at 10Hz. In addition, silicone tube actuators have also been
demonstrated to achieve the necessary displacement, though requiring higher voltages. The choice of electrodes and
prestrain conditions aimed at maximizing axial strain in tube actuators are discussed. Characterization techniques
measuring actuation displacement and blocking forces appropriate for standard Braille cell specifications are presented.
Finally, the integration of these materials into novel cell designs and the fabrication of a prototype Braille cell are
discussed.
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