When a progressive wave of localized deformations occurs tangentially on the fingerpad skin, one typically experiences the illusion of a small object sliding on it. This effect was investigated because of its potential application to the display of Braille. A device was constructed that could produce such deformation patterns along a line. Blind subjects' ability to read truncated Braille characters (‘○○’, ‘○•’, ‘•○’, and ‘••’) using the device was experimentally tested and compared to their performance with a conventional Braille medium. While subjects could identify two-character strings with a high rate of success, several factors need to be addressed before a display based on this principle can become practical.

We present a haptic wristwatch prototype that makes it possible to acquire information from a companion mobile device through simple eyes-free gestures. The wristwatch we have built uses a custom-made piezoelectric actuator combined with sensors to create a natural, inconspicuous, gesture-based interface. Feedback is returned to the user in the form of haptic stimuli that are delivered to the wrist. We evaluated the capabilities and limitations of our prototype through two user experiments. One experiment verified that the apparatus could be used as a tactile notification mechanism. The other experiment assessed the feasibility of using a cover-and-hold gesture on the wristwatch to obtain numerical data tactually. Results from the numerosity experiment and feedback from participants prompted us to redesign the cover-and-hold gesture to provide users with additional control over the interaction. We qualitatively evaluated the redesigned interaction by handing the prototype to users so that they could use it in a realistic work environment. Taken together, results from the experiments and the validation process indicate that a wrist accessory can be effectively used to perform discreet, closed-loop, eyes-free interactions with a mobile device.

Earlier work with a 1-D tactile transducer demonstrated that lateral skin deformation is sufficient to produce sensations similar to those felt when brushing a finger against a line of Braille dots. Here, we extend this work to the display of complete 6-dot Braille characters using a general purpose 2-D tactile transducer called STReSS 2 . The legibility of the produced Braille was evaluated by asking seven expert Braille readers to identify meaningless 5-letter strings as well as familiar words. Results indicate that reading was difficult but possible for most individuals. The superposition of texture to the sensation of a dot improved performance. The results contain much information to guide the design of a specialized Braille display operating by lateral skin deformation. They also suggest that rendering for contrast rather than realism may facilitate Braille reading when using a weak tactile transducer.

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