Braille dot display module with a PDMS membrane driven by a thermopneumatic actuator

Anew type of a Braille dot display module is proposed and evaluated with a poly-dimethylsiloxane(PDMS) membrane driven by a thermopneumatic actuator for six-dot Braille code. Each module consists of four parts: a PDMS reservoir chamber for the working fluid (3M PF-5060), a working fluid, a PDMS membrane (3 mm x 3 mm). and a resistive micro-heater. The module is insulated against the generated heat and allows interoperability with other modules. The deflections of PDMS membranes of different thicknesses, 42, 23, and 15 mu m, are observed while changing the input power to the resistive micro-heater in the range of 0.75-2.5 W. The maximum deflections of PDMS membranes with thicknesses of 42, 23, and 15 mu m are about 1.37, 1.34, and 1.28 mm, respectively, over the substrates at 0.75 W, and slightly decrease to about 1.32, 1.30, and 1.23 mm, respectively, at 2.5 W However, the time required to reach maximum deflection differes greatly with increasing power. At 0.75 W, the response times are 97, 49, and 45 s, respectively. While at 2.5 W, the times are shortened by 16,14, and 13 s, respectively. The achieved deflection is larger than two times of the standard height (600 mu m) designated by the Blind Union in Korea. (C) 2008 Elsevier B.V. All rights reserved.