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The Effects of Structural and Overlay Design Parameters of Membrane Switches on the Force Exerted by Users

Two experiments were conducted to evaluate the effects on applied force of structural design parameters and of feedback conditions inherent in the aesthetic overlay of membrane switch touchpads. In the first experiment which evaluated structure, 12 males and 12 females keyed 100 4-digit sequences into a computer using 6 of a total of 12 touchpads which differed in membrane ply thickness, spacer thickness, and spacer aperture diameter. The same task was completed by nine males and nine females in the second experiment, which evaluated feedback conditions inherent in flat, embossed, domed, embossed with dome, flat with escutcheon, and domed keycap aesthetic overlays. The results have important implications for the methods used for life-testing membrane switch touchpad devices and for the design of touchpads for minimizing user fatigue in extended-use keying applications.