From voice commands and air taps to touch gestures on frames: Various techniques for interacting with head-mounted displays (HMDs) have been proposed. While these techniques have both benefits and drawbacks dependent on the current situation of the user, research on interacting with HMDs has not concluded yet. In this paper, we add to the body of research on interacting with HMDs by exploring foot-tapping as an input modality. Through two controlled experiments with a total of 36 participants, we first explore direct interaction with interfaces that are displayed on the floor and require the user to look down to interact. Secondly, we investigate indirect interaction with interfaces that, although operated by the user's feet, are always visible as they are floating in front of the user. Based on the results of the two experiments, we provide design recommendations for direct and indirect foot-based user interfaces.

Experiencing materials in virtual reality (VR) is enhanced by combining visual and haptic feedback. While VR easily allows changes to visual appearances, modifying haptic impressions remains challenging. Existing passive haptic techniques require access to a large set of tangible proxies. To reduce the number of physical representations, we look towards fabrication to create more versatile counterparts. In a user study, 3D-printed hairs with length varying in steps of 2.5 mm were used to influence the feeling of roughness and hardness. By overlaying fabricated hair with visual textures, the resolution of the user's haptic perception increased. As changing haptic sensations are able to elicit perceptual switches, our approach can extend a limited set of textures to a much broader set of material impressions. Our results give insights into the effectiveness of 3D-printed hair for enhancing texture perception in VR.

The emerging class of epidermal devices opens up new opportunities for skin-based sensing, computing, and interaction. Future design of these devices requires an understanding of how skin-worn devices affect the natural tactile perception. In this study, we approach this research challenge by proposing a novel classification system for epidermal devices based on flexural rigidity and by testing advanced adhesive materials, including tattoo paper and thin films of poly (dimethylsiloxane) (PDMS). We report on the results of three psychophysical experiments that investigated the effect of epidermal devices of different rigidity on passive and active tactile perception. We analyzed human tactile sensitivity thresholds, two-point discrimination thresholds, and roughness discrimination abilities on three different body locations (fingertip, hand, forearm). Generally, a correlation was found between device rigidity and tactile sensitivity thresholds as well as roughness discrimination ability. Surprisingly, thin epidermal devices based on PDMS with a hundred times the rigidity of commonly used tattoo paper resulted in comparable levels of tactile acuity. The material offers the benefit of increased robustness against wear and the option to re-use the device. Based on our findings, we derive design recommendations for epidermal devices that combine tactile perception with device robustness

We introduce Springlets, expressive, non-vibrating mechanotactile interfaces on the skin. Embedded with shape memory alloy springs, we implement Springlets as thin and flexible stickers to be worn on various body locations, thanks to their silent operation even on the neck and head. We present a technically simple and rapid technique for fabricating a wide range of Springlet interfaces and computer-generated tactile patterns. We developed Springlets for six tactile primitives: pinching, directional stretching, pressing, pulling, dragging, and expanding. A study placing Springlets on the arm and near the head demonstrates Springlets’ effectiveness and wearability in both stationary and mobile situations. We explore new interactive experiences in tactile social communication, physical guidance, health interfaces, navigation, and virtual reality gaming, enabled by Springlets’ unique and scalable form factor.

Studying armed political struggles from a CSCW perspective can throw the complex interactions between culture, technology, materiality and political conflict into sharp relief. Such studies highlight interrelations that otherwise remain under-remarked upon, despite their severe consequences. The present paper provides an account of the armed struggle of one of the Colombian guerrillas, FARC-EP, with the Colombian army. We document how radio-based communication became a crucial, but ambiguous infrastructure of war. The sudden introduction of localization technologies by the Colombian army presented a lethal threat to the guerrilla group. Our interviewees report a severe learning process to diminish this new risk, relying on a combination of informed beliefs and significant technical understanding. We end with a discussion of the role of HCI in considerations of ICT use in armed conflicts and introduce the concept of counter-appropriation as process of adapting one's practices to other's appropriation of technology in conflict.