Rendering realistic tactile sensations of virtual objects remains a challenge in VR. While haptic interfaces have advanced, particularly with phased arrays, their ability to create realistic object properties like state and temperature remains unclear. This study investigates the potential of Ultrasound Mid-air Haptics (UMH) for enhancing the perceived congruency of virtual objects. In a user study with 30 participants, we assessed how UMH impacts the perceived material state and temperature of virtual objects. We also analyzed EEG data to understand how participants integrate UMH information physiologically. Our results reveal that UMH significantly enhances the perceived congruency of virtual objects, particularly for solid objects, reducing the feeling of mismatch between visual and tactile feedback. Additionally, UMH consistently increases the perceived temperature of virtual objects. These findings offer valuable insights for haptic designers, demonstrating UMH's potential for creating more immersive tactile experiences in VR by addressing key limitations in current haptic technologies.

Despite irreversibility being omnipresent in the lifeworld, research on interactions making use of irreversibility in computing systems is still in the early stages. User freedom – provided by the undo functionality – is considered to be a pillar of “usable” computer systems, overcoming irreversibility. Within this paper, we set up a thought experiment, challenging the “undo feature” and instead take advantage of irreversibility in the interaction with physical computing systems (tangibles, robots, etc). First, we present three material speculations, each inherently utilizing irreversibility. Second, we elaborate on the concept of irreversible interactions by contextualizing our work with critical HCI discourses and deducing three design strategies. Finally, we discuss irreversibility as a design element for self-reflection, meaningful acting, and a sustainable relationship with technology. While previously individual aspects of irreversibility have been explored, we contribute a comprehensive discussion of irreversible interactions in HCI presenting artifacts, a conceptualization, design strategies, and application purposes.

We present StringTouch, a user interface design exploration translating the expressive resource of string instruments to a new interface morphology. StringTouch transfers the string as a tactile element of interaction to the touch surface, resulting in a tactilely experienceable interface. In this paper we discuss our research through design centered approach, which focused on the exploration of musical string instruments and their translation to the UI context. To investigate this specific design space, we analyzed the systematic and handling of string instruments as well as common HCI principles to develop the interaction concept. The resulting experience prototype demonstrates the idea’s potential for haptic UI design and provides insights into the prototyping process. We present: (1) the investigation of string instruments as a resource for TUI design and (2) the transfer to a generic UI context to inform new hybrid interface morphologies that combine features of tangible, touch, and flexible interaction.

To give robots, which are black box systems for most users, feedback we have to implement interaction paradigms that users understand and accept, for example reward and punishment. In this paper we present the first HRI experience prototype which implements gradual destructive interaction, namely breaking a robot's leg as a punishment technique. We conducted an exploratory experiment (N=20) to investigate participants' behavior during the execution of three punishment techniques. Using a structured analysis of videos and interviews, we provide in-depth insights into participants' attitude towards these techniques. Participants preferred more abstract techniques and felt uncomfortable during human-like punishment interaction. Based on our findings, we raise questions how human-like technologies should be designed. A video documentation of the project can be found here: https://vimeo.com/348646727

This paper introduces a tangible user interface (TUI) concept designed for child-oriented musical interaction and education by the name of COMB. The interaction concept of the interface is based upon the natural behavior and metaphors found in children's play during construction with building-blocks. This paradigm is used to increase the accessibility of the otherwise expert-focused digital and electronic music to children. We evaluated our prototype during two different study setups. We found preliminary indications that this concept fosters imitation during learning. Therefore, the usage of shape as a meaningful element of interaction could be a promising design strategy for interfaces addressing children. In this paper we present the theoretical foundation of the concept as well as technical details of the prototype. Furthermore, we discuss how this concept can be applied to increase accessibility of technology in various other domains.

Low-resolution (low-res) lighting displays are increasingly used by HCI researchers, designers, and in the industry as a versatile and aesthetic medium for deploying ambient interfaces in various contexts. These display types distinguish themselves from conventional high-res screens through: high contrasts, hi-power LED technology which allows visibility even in bright environments, and their ability to take on three-dimensional free forms. However, to date most work on low-res displays has been either of experimental nature or carried out in isolated industry contexts. This paper addresses this gap through an analysis of our own experiences from previous experimental design studies and related work, which led us to five domain challenges for designing low-res displays. We then describe how we approached these challenges in a deployment study, which involved the implementation of a prototype guided by a low-res prototyping toolkit. Based on an analysis of our design process and findings from the deployment study, we present ten design recommendations for low-res lighting displays.

Low-resolution lighting displays are commonplace in internet-of-things devices, wearable products and embedded interfaces. However, prototyping such displays is challenging and cumbersome as methods, specific domain knowledge and skills are only available to experts. In this paper we present a novel toolkit to assist with designing and evaluating the characteristics of low-resolution lighting displays as well as content variations using different materials. We describe the components of the toolkit, which include a tablet, a custom-built app and low-cost prototyping materials, and its use within the context of a design study. The toolkit can easily be replicated and adopted by others working in this domain to prototype low-resolution lighting displays without requiring any previous expertise in hardware prototyping.

Media Architecture is reaching a level of maturity at which we can identify tools and approaches for addressing the main challenges for HCI practitioners working in this field. While previous influential contributions within Media Architecture have identified challenges for designers and offered case studies of specific approaches, here, we (1) provide guidance on how to tackle the domain-specific challenges of Media Architecture design -- pertaining to the interface, integration, content, context, process, prototyping, and evaluation -- on the basis of the development of numerous installations over the course of seven years, and thorough studies of related work, and (2) present five categories of tools and approaches -- software tools, projection, 3D models, hardware prototyping, and evaluation tools -- developed to address these challenges in practice, exemplified through six concrete examples from real-life cases.

In this work we present our approach for creating interactive media façades by using purpose-built tools. They are intended to create prototypes and conduct field investigations in this domain. We share our vision of an extended design process which describes ways to engage large user groups by urban prototyping and experience novel interventions in public places. Architects, designers and researchers can receive first hand insights into the suitability of their chosen interaction design concept for media architecture by using our tools and approach.

There is a well-established culture of early prototyping when designing digital interactive systems, such as paper prototyping and wireframe methods. The culture of designing physical objects is somewhat different: early explorations of form is still prototyped via 2D sketches or renderings, but - mostly because of the construction effort involved - prototyping of actual physical objects is deferred to later stages. A problem occurs when designing mixed physical-digital systems, such as tangible user interfaces (TUIs) on interactive surfaces: the high degree of interactivity means that early prototyping is vital, yet there is no viable process for prototyping both the physical and digital aspects simultaneously on a low-fidelity (low-fi) level. Our solution is Paperbox, a toolkit for exploring design ideas for tangible interaction on interactive surfaces. It supports the early exploration of different form factors and immediately provides digital interactivity for the low-fidelity TUI prototypes built with it. We observed our toolkit in use in various settings: as a brainstorming tool by junior designers; in the development of a consumer electronics product in a large industrial company by senior designers; and in a usability study comparing the effect of different levels of fidelity on the outcome. The lessons learnt will enable others to replicate and extend our approach.

LED-based lighting systems have introduced radically new possibilities in the area of artificial lighting. Being physically small the LED can be positioned or embedded into luminaires, materials and even the very fabric of a building or environment. Hundreds of LEDs can be used in a single luminaire or space, of which each could have different light output properties. The light switch therefore in many situations will need to be enhanced or fully replaced by intelligent controls and smart environments that are sensitive to the context and responsive to the people in the environment. The focus of this workshop is to explore new ways of interacting with light where lighting is no longer simply an on or off system, but a flexible system capable of creating a large range of functional, decorative and ambient light effects.

Media façades are one prominent example of how new technologies currently augment urban spaces. At the same time, they offer new, ubiquitous opportunities for novel applications. To achieve a usable and enjoyable outcome, however, designing interaction with media façades demands a structured design process. In this paper, we present our experiences designing iRiS, a system for remote interaction with media façades. We approached the development following a user-centered design approach and addressing the process at two points with additional means: (1) using a purpose-built prototyping toolkit testing and exploring both, content and hardware before deploying the system on the actual façade and (2) experimental use and adaptation of user experience (UX) evaluation methods to investigate the users actions and emotions more holistically in this context.

Graspable tangibles are now being explored on the current generation of capacitive touch surfaces, such as the iPad and the Android tablet. Because the size and form factor is relatively new, early and low fidelity prototyping of these TUIs is crucial in getting the right design. The problem is that it is difficult for the average interaction designer to develop such physical prototypes. They require a substantial amount time and effort to physically model the tangibles, and expertise in electronics to instrument them. Thus prototyping is sometimes handed off to specialists, or is limited to only a few design iterations and alternative designs. Our solution contributes a low fidelity prototyping approach that is time and cost effective, and that requires no electronics knowledge. First, we supply non-specialists with cardboard forms to create tangibles. Second, we have them draw lines on it via conductive ink, which makes their objects recognizable by the capacitive touch screen. They can then apply routine programming to recognize these tangibles and thus iterate over various designs.

The increasing number of media facades in urban spaces offers great potential for new forms of interaction especially for collaborative multi-user scenarios. In this paper, we present a way to directly interact with them through live video on mobile devices. We extend the Touch Projector interface to accommodate multiple users by showing individual content on the mobile display that would otherwise clutter the facade's canvas or distract other users. To demonstrate our concept, we built two collaborative multi-user applications: (1) painting on the facade and (2) solving a 15-puzzle. We gathered informal feedback during the ARS Electronica Festival in Linz, Austria and found that our interaction technique is (1) considered easy-to-learn, but (2) may leave users unaware of the actions of others.

Multi-touch screens and surfaces for manipulating digital content play a crucial role in mobile and ubiquitous computing. Augmenting these interactive surfaces with tactile feedback has been found to increase interaction speed, reduce operating errors and minimize visual and cognitive load. Communicating detailed tactile characteristics of virtual elements, however, requires complex electromechanical or electrostatic actuator setups. This increase in complexity makes tactile interfaces intricate, costly or poorly scalable. In order to provide sophisticated tactile sensations with simple actuator technology, we exploit a haptic psychophysical phenomenon called Phantom Sensation. We present a comparison of three standard tactile actuator technologies to see which one can recreate the Phantom Sensation with maximum effect. Our results show the way to a simple and scalable implementation of illusion-based tactile feedback for interactive surfaces. We explore the notion of the Phantom Sensation and its possible applications within a ubicomp scenario.

In this paper we describe a prototype for the simple and playful exploration of various interaction modalities with colored light.

In this paper we present inTUIt experience prototyping approach to investigate different simple identification techniques for tangible user interfaces (TUI) on digital surfaces. We have developed four different experience prototypes, proposing alternative approaches to the establishment of temporary ownership of digital content and TUIs in public environments.

Near Field Communication (NFC) can facilitate mobile interaction with everyday objects, associated digital information and ubiquitous services. Despite the simplicity of the touch-like interaction between mobile devices and tagged physical objects, most people are still unfamiliar with this physical interaction, resulting in various usability problems. In order to improve mobile interaction with NFC-tagged objects, that serve as physical user interfaces (UI), we examine various aspects of their visual design. We identify different phases of mobile interaction with tagged objects and apply a user centered design process to create and evaluate different symbols for these phases. We report on the iterative design of NFC-symbols and physical UIs using low- and high-fidelity prototyping and present the results of a user study which was carried out with an experience prototype for an advertising scenario.