Seeking the ‘holy Braille’ display: might electromechanically active polymers be the solution?

Figures & data

Figure 1. Lateral view of a typical piezo bimorph Braille cell.

Table 1. Specifications of Braille dot parameters for refreshable Braille displays.

Parameter	Minimum (mm)	Nominal (mm)	Maximum (mm)	Typical (mm)
Dot base diameter	1.4	1.5	1.6	1.5
Dot height (assuming no depression force from user’s finger)	0.48	0.5	0.9	0.7
Dot height uniformity for adjacent dots	–	–	–	±0.05
Distance between centers of perpendicularly adjacent dots in the same cell	2.3	2.5	2.6	2.45
Distance between centers of corresponding dots in horizontally adjacent cells	6.1	6.35	6.5	6.42
Height of eight-dot Braille cell lines	12.25	13.25	13.75	13
Radius of curvature of the dot dome	–	–	–	0.6–0.8

Table 2. Overview of key strategies being studied to develop electromechanically active polymer-driven refreshable Braille displays.

EAP family	EAP material	Actuator configuration	Ref.
Ionic	Conjugated polymers	Cylinder	[8]
	Ionic polymer metal composites	Bender	[9]
Electronic	Electrostrictive polymers	Roll with spring core	[10]
	Piezoelectric polymers	Bender with hydraulic coupling	[11]
	Dielectric elastomers	Cylinder	[11]
		Diaphragm	[12]
		Buckling membrane	[13]
		Planar multilayer stack	[14]
		Bistable diaphragm	[15]
		Hydrostatically coupled membranes	[16]

EAP: Electromechanically active polymer.

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