Publikationen von Dennis Stanke

Social events such as cocktail parties are valuable opportunities to build and sustain interpersonal relationships. However, meeting new people, the self-mixing of cocktails, and tracking one's beverage consumption can be difficult and intimidating. To support users during social events, we introduce CheersMate, a smart drinking glass that enables the simultaneous use of a private and a public wearable display. The private display provides cocktail mixing guidance to the user and shows personal consumption statistics during conversations, while the public display encourages social interaction by revealing the user's name and current drink. By clinking two CheersMates, the user can transfer additional information from the private to the public display, for example, showing the number of people the user has toasted with and the number of already consumed drinks. A pilot study with eight participants provides first insights on the acceptance of our concept and on the perceived usefulness as a social catalyst.

Smart devices accompany us in everyday life, providing information from all over the world. While the size of smartphones keeps increasing, the size of wearable devices is not only limited by the physical space available on the wearer's body, but also restricted by factors like weight and comfort for the user. When interacting with smart wearable devices, such as smartwatches, occluding the majority of the touchscreen during usage is one of the major problems. For complex interactions, like map navigation tasks, the occlusion even increases due to multi-touch input. Therefore, the content shown on the screen and the feedback the user receives has to be as concise as possible so that the user still is aware of the changes on the screen during the interaction. As wearable devices are designed to present information only to the wearer, showing the information on the screen to other people remains an additional challenge. For instance, presenting the current heart-rate reading from a smartwatch to a fitness trainer during exercise inevitably forces the user to twist their arm in an unnatural way. This dissertation highlights the potential of private and public wearable displays. First, we describe the terminology and position private and public wearable displays within the context of private and public displays. For private wearable displays, we then analyze whether different smartwatch sizes and the presence of a bezel impacts the occlusion and task completion times during multi-touch input. To address the occlusion problem, we propose two approaches that succeeded in increasing the visible display space during usage while also maintaining shorter or equal task completion times compared to classic touch input. To reduce the necessity of visual notifications on the screen, we provide an analysis of spatial electrotactile feedback as an alternative output method to vibration feedback. We evaluate spatial electrotactile feedback around the wrist and ring finger by comparing it with vibration feedback and give recommendations on different notification pattern. Further, we explore the electrotactile funneling illusion on the forearm and give details on effective distances. For public wearable displays, we propose different usage scenarios and designs to improve the social acceptability and overall experience of sharing information to people nearby. Therefore, we investigate the use of headphones as public wearable displays by exploring usage scenarios, social acceptability, and different designs for content shown on a display that is attached to or integrated into the earpieces. Further, we propose the use of ear-clips for smart wearable devices and evaluate their potential for delivering private notifications to the wearer and public notifications to people nearby. Finally, we explore the simultaneous use of private and public wearable displays in two scenarios. We propose showing reduced information from the private wearable display on the public wearable display as well as the option to naturally reveal additional information whenever the user chooses.

On the skin, a small distance between two actuators can result in the perception of a single, centralized stimulus rather than two distinct stimuli – this phenomenon is known as the funneling illusion. In this work, we explore the electrotactile funneling illusion on the forearm in a user study with 16 participants. We placed an electrode strip with 9 electrode pairs along their forearm – from wrist to elbow. The calibration of the same perceived intensity of each electrode pair for each participant shows that the calibrated intensities near the wrist are significantly higher compared to the intensities calibrated near the elbow. A linear regression corresponds to this behavior as well as the qualitative feedback of our participants. Based on this, we created an equation that helps to reduce the calibration time considerably. The results of our study show that the funneling illusion can be reliably evoked at distances of up to 7.2cm. Further, we provide detailed information on occurrence frequency and precision and explored whether an approach adapted for electrotactile feedback can create an apparent tactile motion.

Operating small touchscreens with the finger occludes a large part of the screen. We propose using the watch case as the input space, without enlarging the smartwatch. Therefore, we created two prototypes, one with a touch surface on the watch case (CASE) and one with touch surfaces on the watch case and the wristband (CASE+BAND). In a comparative study, we analyze their suitability in a 1D list scrolling task and 2D map navigation task. The results show that occlusion is less of a problem for the list scrolling task, as visibility is sufficient. In the map navigation task, participants reached task completion times with CASE+BAND that are comparable to touch input. CASE was significantly slower, but only requires minimal additional hardware. However, the results of a subsequent longitudinal study demonstrates the learnability of CASE, which led to task completion times comparable to touch input, and provides insights in the gradual development of expert performance.

Cycling navigation is a complex and stressful task as the cyclist needs to focus simultaneously on the navigation, the road, and other road users. We propose directional electrotactile feedback at the wrist to reduce the auditory and visual load during navigation-aided cycling. We designed a custom electrotactile grid with 9 electrodes that is clipped under a smartwatch. In a preliminary study we identified suitable calibration settings and gained first insights about a suitable electrode layout. In a subsequent laboratory study we showed that a direction can be encoded with a mean error of 19.28° (σ = 42.77°) by combining 2 adjacent electrodes. Additionally, by interpolating with 3 electrodes a direction can be conveyed with a similar mean error of 22.54° (σ = 43.57°). We evaluated our concept of directional electrotactile feedback for cyclists in an outdoor study, in which 98.8% of all junctions were taken correctly by eight study participants. Only one participant deviated substantially from the optimal path, but was successfully navigated back to the original route by our system.

The earlobe is a well-known location for wearing jewelry, but might also be promising for electronic output, such as presenting notifications. This work elaborates the pros and cons of different notification channels for the earlobe. Notifications on the earlobe can be private (only noticeable by the wearer) as well as public (noticeable in the immediate vicinity in a given social situation). A user study with 18 participants showed that the reaction times for the private channels (Poke, Vibration, Private Sound, Electrotactile) were on average less than 1 s with an error rate (missed notifications) of less than 1 %. Thermal Warm and Cold took significantly longer and Cold was least reliable (26 % error rate). The participants preferred Electrotactile and Vibration. Among the public channels the recognition time did not differ significantly between Sound (738 ms) and LED (828 ms), but Display took much longer (3175 ms). At 22 % the error rate of Display was highest. The participants generally felt comfortable wearing notification devices on their earlobe. The results show that the earlobe indeed is a suitable location for wearable technology, if properly miniaturized, which is possible for Electrotactile and LED. We present application scenarios and discuss design considerations. A small field study in a fitness center demonstrates the suitability of the earlobe notification concept in a sports context.

The need for online meetings increased drastically during the COVID-19 pandemic. Wearing headphones for this purpose makes it difficult to know when a headphone wearing person is available or in a meeting. In this work, we explore the design possibilities of headphones as wearable public displays to show the current status or additional information of the wearer to people nearby. After two brainstorming sessions and specifying the design considerations, we conducted an online survey with 63 participants to collect opinions of potential users. Besides the preference of the colors red and green as well as using text to indicate availability, we found that only 54 % of our participants would actually wear headphones with public displays attached. The benefit of seeing the current availability status of a headphone-wearing person in an online meeting or phone call scenario were nonetheless mentioned even by participants that would not use such headphones.

A common problem of touch-based smartwatch interaction is the occlusion of the display. Although some models provide solutions like the Apple "digital crown" or the Samsung rotatable bezel, these are limited to only one degree of freedom (DOF). Performing complex tasks like navigating on a map is still problematic as the additional input option helps to zoom, but touching the screen to pan the map is still required. In this work, we propose using a trackball as an additional input device that adds two DOFs to prevent the occlusion of the screen. We created several prototypes to find a suitable placement and evaluated them in a typical map navigation scenario. Our results show that the participants were significantly faster (15.7%) with one of the trackball setups compared to touch input. The results also show that the idle times are significantly higher with touch input than with all trackball prototypes, presumably because users have to reorient themselves after panning with finger occlusion.

Wearables are getting more and more powerful. Tasks like notifications can be delegated to smartwatches. But the output capabilities of wearables seem to be stuck at displays and vibration. Electrotactile feedback may serve as an energy-efficient alternative to standard vibration feedback. We developed prototypes of wristbands and rings and conducted two studies to compare electrotactile and vibrotactile feedback. The prototypes have either four electrodes for electrotactile feedback or four actuators for vibration feedback. In a first study we analyzed the localization characteristics of the created stimuli. The results suggest more strongly localized sensations for electrotactile feedback, compared to vibrotactile feedback, which was more diffuse. In a second study we created notification patterns for both modalities and evaluated recognition rates, verbal associations, and satisfaction. Although the recognition rates were higher with electrotactile feedback, vibrotactile feedback was judged as more comfortable and less stressful. Overall, the results show that electrotactile feedback can be a viable alternative to vibrotactile feedback for wearables, especially for notification rings.

Current soft keyboards for emoji entry all present emoji in the same way: in long lists, spread over several categories. While categories limit the number of emoji in each individual list, the overall number is still so large, that emoji entry is a challenging task. The task takes particularly long if users pick the wrong category when searching for an emoji. Instead, we propose a new zooming keyboard for emoji entry. Here, users can see all emoji at once, aiding in building spatial memory where related emoji are to be found. We compare our zooming emoji keyboard against the Google keyboard and find that our keyboard allows for 18% faster emoji entry, reducing the required time for one emoji from 15.6s to 12.7s. A preliminary longitudinal evaluation with three participants showed that emoji entry time over the duration of the study improved at up to 60% to a final average of 7.5s.