To support seamless mixed reality (MR) interactions without obstructing natural touch, we introduce PhantomFolds, a nail-mounted device featuring two linear resonant actuators (LRAs) at the lateral nail folds that provide spatio-tactile feedback for in-air as well as on-surface interactions in MR. In three studies, we investigate the perception of spatio-tactile feedback produced by PhantomFolds. Our results show that (1) PhantomFolds can leverage the funneling illusion to produce spatio-tactile feedback at the finger for in-air as well as on-surface interactions, (2) tactile feedback produced with PhantomFolds can successfully increase the perceived realism in MR applications without impeding user interaction, (3) phantom sensations, are perceived more localized when users touch a surface, and (4) while participants could not consistently feel touch illusions below the finger when touching a surface as described by prior work, our results indicate that a per-user calibration could increase the success rate of this effect in the future.

Tickling is a type of sensation that is associated with laughter, smiling, or other similar reactions. Psychology research has shown that tickling and laughter can significantly relieve stress. Although several tickling artifacts have been suggested in prior work, limited knowledge is available if those artifacts could evoke laughter. In this article, we aim at filling this gap by designing and developing a novel foot-tickling mechanism that can evoke laughter. We first developed an actuator that can create tickling sensations along the sole of the foot utilising magnet-driven brushes. Then, we conducted two studies to identify the most ticklish locations of the foot’s sole and stimulation patterns that can evoke laughter. In a follow-up study with a new set of participants, we confirmed that the identified stimuli could evoke laughter. From the participants’ feedback, we derived several applications that such a simulation could be useful. Finally, we embedded our actuators into a flexible insole, demonstrating the potential of a wearable tickling insole.

Emerging research has demonstrated the viability of on-textile actuation mechanisms, however, an easily customizable and versatile on-cloth actuation mechanism is yet to be explored. In this paper, we present ClothTiles along with its rapid fabrication technique that enables actuation of clothes. ClothTiles leverage flexible 3D-printing and Shape-Memory Alloys (SMAs) alongside new parametric actuation designs. We validate the concept of fabric actuation using a base element, and then systematically explore methods of aggregating, scaling, and orienting prospects for extended actuation in garments. A user study demonstrated that our technique enables multiple actuation types applied across a variety of clothes. Users identified both aesthetic and functional applications of ClothTiles. We conclude with a number of insights for the Do-It-Yourself community on how to employ 3D-printing with SMAs to enable actuation on clothes.

We present a wearable forearm augmentation that enables the recreation of natural touch sensation by applying shear-forces onto the skin. In contrast to previous approaches, we arrange light-weight and stretchable 3x3cm plasters in a matrix onto the skin. Individual plasters were embedded with lines of shape-memory alloy (SMA) wires to generate shear-forces. Our design is informed by a series of studies investigating the perceptibility of different sizes, spacings, and attachments of plasters on the forearm. Our matrix arrangement enables the perception of touches, for instance, feeling ones wrist being grabbed or the arm being stroked. Users rated the recreated touch sensations as being fairly similar to a real touch (4.1/5). Even without a visual representation, users were able to correctly distinguish them with an overall accuracy of 94.75%. Finally, we explored two use cases showing how AR and VR could be empowered with experiencing recreated touch sensations on the forearm.

Sensing interfaces relying on head or facial gestures provide effective solutions for hands-free scenarios. Most of these interfaces utilize sensors attached to the face, as well as into the mouth, being either obtrusive or limited in input bandwidth. In this paper, we propose ChewIt -- a novel intraoral input interface. ChewIt resembles an edible object that allows users to perform various hands-free input operations, both simply and discreetly. Our design is informed by a series of studies investigating the implications of shape, size, locations for comfort, discreetness, maneuverability, and obstructiveness. Additionally, we evaluated potential gestures that users could use to interact with such an intraoral interface.

The correct execution of exercises, such as squats and dead-lifts, is essential to prevent various bodily injuries. Existing solutions either rely on expensive motion tracking or multiple Inertial Measurement Units (IMU) systems require an extensive set-up and individual calibration. This paper introduces a proof of concept, GymSoles, an insole prototype that provides feedback on the Centre of Pressure (CoP) at the feet to assist users with maintaining the correct body posture, while performing squats and dead-lifts. GymSoles was evaluated with 13 users in three conditions: 1) no feedback, 2) vibrotactile feedback, and 3) visual feedback. It has shown that solely providing feedback on the current CoP, results in a significantly improved body posture.

EarFieldSensing (EarFS) is a novel input method for mobile and wearable computing using facial expressions. Facial muscle movements induce both electric field changes and physical deformations, which are detectable with electrodes placed inside the ear canal. The chosen ear-plug form factor is rather unobtrusive and allows for facial gesture recognition while utilizing the close proximity to the face. We collected 25 facial-related gestures and used them to compare the performance levels of several electric sensing technologies (EMG, CS, EFS, EarFS) with varying electrode setups. Our developed wearable fine-tuned electric field sensing employs differential amplification to effectively cancel out environmental noise while still being sensitive towards small facial-movement-related electric field changes and artifacts from ear canal deformations. By comparing a mobile with a stationary scenario, we found that EarFS continues to perform better in a mobile scenario. Quantitative results show EarFS to be capable of detecting a set of 5 facial gestures with a precision of 90% while sitting and 85.2% while walking. We provide detailed instructions to enable replication of our low-cost sensing device. Applying it to different positions of our body will also allow to sense a variety of other gestures and activities.

Foot interfaces, such as pressure-sensitive insoles, still yield unused potential such as for implicit interaction. In this paper, we introduce CapSoles, enabling smart insoles to implicitly identify who is walking on what kind of floor. Our insole prototype relies on capacitive sensing and is able to sense plantar pressure distribution underneath the foot, plus a capacitive ground coupling effect. By using machine-learning algorithms, we evaluated the identification of 13 users, while walking, with a confidence of ∼95% after a recognition delay of ∼1s. Once the user's gait is known, again we can discover irregularities in gait plus a varying ground coupling. While both effects in combination are usually unique for several ground surfaces, we demonstrate to distinguish six kinds of floors, which are sand, lawn, paving stone, carpet, linoleum, and tartan with an average accuracy of ∼82%. Moreover, we demonstrate the unique effects of wet and electrostatically charged surfaces.

We present Botential, an on-body interaction method for a wearable input device that can identify the location of on-body tapping gestures, using the entire human body as an interactive surface to expand the usually limited interaction space in the context of mobility. When the sensor is being touched, Botential identifies a body part's unique electric signature, which depends on its physiological and anatomical compositions. This input method exhibits a number of advantages over previous approaches, which include: 1) utilizing the existing signal the human body already emits, to accomplish input with various body parts, 2) the ability to also sense soft and long touches, 3) an increased sensing range that covers the whole body, and 4) the ability to detect taps and hovering through clothes.

Over the past few years the use of public displays has increased drastically, with the most common public displays being flat surface LED walls or projections on walls. Presently interactive public displays often make use of depth cameras. This paper introduces a cheaper variant that allows people to interact with the display and each other by using the color detection abilities of an ordinary webcam. As proof of concept a simple game was created that demonstrates how people are able to control and interact with photographed shapes via their own smartphones. Alternately a special hardware interface was built for users who do not own a smartphone. Contrary to ordinary games, this game works without points; instead, the leading user is awarded the ability to make decisions about game speed and is able to influence the audio through his movements.

ShoeSoleSense is a proof of concept, novel body worn interface - an insole that enables location independent hands-free interaction through the feet. Forgoing hand or finger interaction is especially beneficial when the user is engaged in real world tasks. In virtual environments as moving through safety training applications is often conducted via finger input, which is not very suitable. To enable a more intuitive interaction, alternative control concepts utilize gesture control, which is usually tracked by statically installed cameras in CAVE-like-installations. Since tracking coverage is limited, problems may also occur. The introduced prototype provides a novel control concept for virtual reality as well as real life applications. Demonstrated functions include movement control in a virtual reality installation such as moving straight, turning and jumping. Furthermore the prototype provides additional feedback by heating up the feet and vibrating in dedicated areas on the surface of the insole.