Design and microfabrication of a flexible oral electrotactile display

A polyimide-based flexible oral tactile display with an array of 7×7 tactors is designed for presentation of electrotactile patterns onto the roof of the mouth. The device is microfabricated on a rigid substrate using thin-film and electroplating processes and then released by peeling it off from the substrate. Dome-shaped tactors are electroplated through round openings 300 μm in diameter in the flexible polyimide base for more uniform current distribution and better contact with the skin. The overall dimensions of the tactor array are 18.5×18.5 mm², with a center-to-center spacing of 2.54 mm between adjacent tactors. Each tactor is 200 μm in height and 700 μm in diameter. The device robustness is improved by using a grid-pattern design for the openings to overcome the stress mismatch between the rigid tactors and the flexible base. The flexible oral tactile display has been tested in human subject experiments and found to deliver comfortable electrotactile stimulation with relatively low stimulation intensities.