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Adding expressive haptic feedback to mobile devices has great potential to improve their usability, particularly in multitasking situations where one’s visual attention is required. Piezoelectric actuators are emerging as one suitable technology for rendering expressive haptic feedback on mobile devices.
We describe the design of redundant piezoelectric haptic augmentations of touchscreen GUI buttons, progress bars, and scroll bars, and their evaluation under varying cognitive load. Our haptically augmented progress bars and scroll bars led to significantly faster task completion, and favourable subjective reactions.
We further discuss resulting insights into designing useful haptic feedback for touchscreens and highlight challenges, including means of enhancing usability, types of interactions where value is maximized, difficulty in disambiguating background from foreground signals, tradeoffs in haptic strength vs. resolution, and subtleties in evaluating these types of interactions.