Project 3
Micro-Valve Array for a Reconfigurable Tactile Tablet for Vision Impaired Individuals
(Prof. S. Mcnamara, ECE - DREAM LAB)
Micro-valve concept. (a) A bilayer containing a tensile and compressive film naturally coils due to the stress mis-match. (b) Placed over a hole in the substrate, the bilayer, when coiled, will let air pass through the hole. However, when a voltage is applied, the electrostatic forces unroll the bilayer, closing the valve. [1]
Every minute a child goes blind somewhere in the world. Visual impairment has huge costs, both personally and to society at large. Even in the U.S., only 30% of visually impaired people have jobs. One major obstacle leading to a widening gap between sighted and blind student is that the blind do not have equal access to information. Without an easy way to learn abstract mathematical concepts while in school, career options narrow. Although Braille readers exist, they are extremely limited when it comes to representing graphical information.
In this research project, we will work on a new mechanism for actuating Braille pins or Braille dimples on a flat surface using pneumatic actuation. Our lab is working on a MEMS Micro-Valve Array for this application, shown in Figure 1 [1]. The micro-valve array is a 2-D array of micro-valves that control the flow of air from one side of a substrate to the other side.
Our research group is developing a micro-valve array based on a strained bilayer film that overcomes the aforementioned limitations. A strained bilayer film is used because the film can become tightly coiled [2], occupying a minimum volume adjacent to the gas channel. The micro-valve is actuated by applying a voltage between the substrate and strained bilayer film, causing the film unroll and cover a gas channel. When the voltage is removed, the strained bilayer film rolls up, uncovering the gas channel. The amount of coverage of the gas channel can be controlled by varying the voltage. In this manner, each gas channel can be individually controlled allowing for a variety of grayscale tactile images to be made, thus assisting visually impaired individuals in their ability to sense an image.
Kentucky is fairly unique because the American Printing House for the Blind (APH) is located in downtown Louisville, KY. In 1879, Congress passed the Act to Promote the Education of the Blind, which designates APH as the official supplier of education materials to the blind for all students below the college level.
Schematic and photographs of the pneumatic valve as it lays flat and in the coiled position. [1]
References
[1] J. D. Schneider, J. D. Rebolledo-Mendez, and S. McNamara, "A grayscale pneumatic micro-valve for use in a reconfigurable tactile tablet for vision-impaired individuals," Journal of Micromechanics and Microengineering, vol. 25, p. 015008, 2015.
[2] M. Huang, C. Boone, M. Roberts, D. E. Savage, M. G. Lagally, N. Shaji, et al., "Nanomechanical Architecture of Strained Bilayer Thin Films: From Design Principles to Experimental Fabrication," Advanced Materials, vol. 17, pp. 2860-2864, 2005.
