Many finger sensing input devices now support proximity input, enabling users to perform in-air gestures. While near-surface interactions increase the input vocabulary, they lack tactile feedback, making it hard for users to perform gestures or to know when the interaction takes place. Sparkle stimulates the fingertip with touchable electric arcs above a hover sensing device to give users in-air tactile or thermal feedback, sharper and more feelable than acoustic mid-air haptic devices. We present the design of a high voltage resonant transformer with a low-loss soft ferrite core and self-tuning driver circuit, with which we create electric arcs 6 mm in length, and combine this technology with infrared proximity sensing in two proof-of-concept devices with form factor and functionality similar to a button and a touchpad. We provide design guidelines for Sparkle devices and examples of stimuli in application scenarios, and report the results of a user study on the perceived sensations. Sparkle is the first step towards providing a new type of hover feedback, and it does not require users to wear tactile stimulators.

Virtual navigation on a mobile touchscreen is usually performed using finger gestures: drag and flick to scroll or pan, pinch to zoom. While easy to learn and perform, these gestures cause significant occlusion of the display. They also require users to explicitly switch between navigation mode and edit mode to either change the viewport's position in the document, or manipulate the actual content displayed in that viewport, respectively. SidePress augments mobile devices with two continuous pressure sensors co-located on one of their sides. It provides users with generic bidirectional navigation capabilities at different levels of granularity, all seamlessly integrated to act as an alternative to traditional navigation techniques, including scrollbars, drag-and-flick, or pinch-to-zoom. We describe the hardware prototype, detail the associated interaction vocabulary for different applications, and report on two laboratory studies. The first shows that users can precisely and efficiently control SidePress; the second, that SidePress can be more efficient than drag-and-flick touch gestures when scrolling large documents.

The Power-up Button is a physical button that combines pressure and proximity sensing to enable gestural interaction with one thumb. Combined with a gesture recognizer that takes the hand's anatomy into account, the Power-up Button can recognize six different mid-air gestures performed on the side of a mobile device. This gives it, for instance, enough expressive power to provide full one-handed control of interface widgets displayed on screen. This technology can complement touch input, and can be particularly useful when interacting eyes-free. It also opens up a larger design space for widget organization on screen: the button enables a more compact layout of interface components than what touch input alone would allow. This can be useful when, e.g., filling the numerous fields of a long Web form, or for very small devices.

In many sports, athletes are spatially separated from their coach while practicing an exercise. This spatial separation makes learning new skills arduous because the coach cannot give instructions or feedback on performance. We present the findings of an in the wild study that demonstrate the potential for teaching sport skills with realtime tactile instructions. We focused on snowboard training. Ten amateurs learned a riding technique with a wearable system that automatically provided tactile instructions during descents. These instructions were in sync with the movements of the snowboard and signaled how to move the body. We found that tactile instructions could help snowboarders to improve their skills. We report insights into the snowboarders' opinion and give recommendations for teaching sport skills with tactile instructions. Our findings help to identify the conditions under which tactile instructions can support athletes in sports training.

TypeRight is a new tactile input device for text entry. It combines the advantages of tactile feedback with error prevention methods of word processors. TypeRight extends the standard keyboard so that the resistance to press each key becomes dynamically adjustable through software. Before each keystroke, the resistance of keys that would lead to a typing error according to dictionary and grammar rules is increased momentarily to make them harder to press, thus avoiding typing errors rather than indicating them after the fact. Two user studies showed that TypeRight decreases error correction rates by an average of 46%.

While learning new motor skills, we often rely on feedback from a trainer. Auditive feedback and demonstrations are used most frequently, but in many domains they are inappropriate or impractical. We introduce tactile instructions as an alternative to assist in correcting wrong posture during physical activities, and present a set of full-body vibrotactile patterns. An initial study informed the design of our tactile patterns, and determined appropriate locations for feedback on the body. A second experiment showed that users perceived and correctly classified our tactile instruction patterns in a relaxed setting and during a cognitively and physically demanding task. In a final experiment, snowboarders on the slope compared their perception of tactile instructions with audio instructions under real-world conditions. Tactile instructions achieved overall high recognition accuracy similar to audio instructions. Moreover, participants responded quicker to instructions delivered over the tactile channel than to instructions presented over the audio channel. Our findings suggest that these full-body tactile feedback patterns can replace audio instructions during physical activities.

Tactile motion instructions are vibrotactile feedback patterns delivered across the entire body that indicate how to move during physical activities. This work investigates the perception and identification of such patterns, based on two different metaphors, under stationary and active situations. We further combine and sequentially trigger different patterns to explore whether tactile motion instructions are understandable as a simple language. A tactile language could represent motion sequences to guide students during demanding exercises. Finally, the presented studies provide insights into perception and interpretation of tactile feedback and help to inform a design space for full-body vibrotactile cues.