Extended Reality (XR) has advanced audiovisual immersion, yet haptic feedback, especially for the lower body, remains limited. We present RoboHaptics, the first system to explore lower-body haptics using commercial quadruped robots. RoboHaptics leverages its freestanding and reconfigurable nature to deliver both active and passive tactile feedback without requiring worn devices. We contribute a design space for quadruped-mediated haptics, a software toolkit with a programmable library of tactile effects, and empirical evaluations showing that quadruped robots can deliver safe force feedback from 3–28 N (below nociceptive thresholds), reach lower-body locations with precision of 2.1–5.1 mm and accuracy of 3.7–17 mm, and support a wide range of tactile effects. A 12-participant study further revealed significant inputs into how RoboHaptics can be used to increase realism and immersion by providing lower-body haptic feedback. Together, our work establishes quadruped robots as a versatile platform for mobile, off-body haptics in XR.

Figure 1: LightLink enables adding different sensor and actuator add-ons to a smartwatch: (a) shows a person blowing into a bezel mounted alcohol sensor for on-demand breath alcohol level measurement; (b) four button user interface attached to the watch strap for eyes-free interaction; (c) Tilt switch sensor band attached to the forearm to track reps count in exercises; (d) Vibration band attached to the forearm to deliver haptic patterns; (e) LED display add-on attached to the watch strap for quicker and easier viewing of notifications/navigation instructions.

We explore the potential for subtle on-hand gesture and microgesture interactions for map navigation with augmented reality (AR) devices. We describe a design exercise and follow-up elicitation study in which we identified on-hand gestures for cartographic interaction primitives. Microgestures and on-hand interactions are a promising space for AR map navigation as they offers always-available, tactile, and memorable spaces for interaction. Our findings show a clear set of microgesture interaction patterns that are well suited for supporting map navigation and manipulation. In particular, we highlight how the properties of various microgestures align with particular cartographic interaction tasks. We also describe our experience creating an exploratory proof-of-concept AR map prototype which helped us identify new opportunities and practical challenges for microgesture control. Finally, we discuss how future AR map systems could benefit from on-hand and microgesture input schemes.

We report findings from initial exploration into using electrotactile stimulation, on the surgeon's tongue, as a potential lower-latency and less mechanically-complex way to provide force-feedback to the operator of robot-assisted surgery. We conducted a pilot feasibility study wherein participants attempted to teleoperate a robot to grasp and lift chicken eggs without breaking or dropping them. The force measured by the robot's gripper was displayed differently based on the experimental condition: visually only, or visually with electrotactile tongue stimulation. Participants were more successful lifting eggs with tongue stimulation. Data from this preliminary study, along with insights from informal interviews, suggest that tongue stimulation has potential to enhance the efficacy and safety of robot-assisted surgery.

The development of low-cost and non-invasive biosensors for monitoring electrochemical biomarkers in sweat holds great promise for personalized healthcare and early disease detection. In this work, we present ecSkin, a novel fabrication approach for realizing epidermal electrochemical sensors that can detect two vital biomarkers in sweat: glucose and cortisol. We contribute the synthesis of functional reusable inks, that can be formulated using simple household materials. Electrical characterization of inks indicates that they outperform commercially available carbon inks. Cyclic voltammetry experiments show that our inks are electrochemically active and detect glucose and cortisol at activation voltages of -0.36 V and -0.22 V, respectively. Chronoamperometry experiments show that the sensors can detect the full range of glucose and cortisol levels typically found in sweat. Results from a user evaluation show that ecSkin sensors successfully function on the skin. Finally, we demonstrate three applications to illustrate how ecSkin devices can be deployed for various interactive applications.

Sustainable fabrication approaches and biomaterials are increasingly being used in HCI to fabricate interactive devices. However, the majority of the work has focused on integrating electronics. This paper takes a sustainable approach to exploring the fabrication of biochemical sensing devices. Firstly, we contribute a set of biochemical formulations for biological and environmental sensing with bio-sourced and environment-friendly substrate materials. Our formulations are based on a combination of enzymes derived from bacteria and fungi, plant extracts and commercially available chemicals to sense both liquid and gaseous analytes: glucose, lactic acid, pH levels and carbon dioxide. Our novel holographic sensing scheme allows for detecting the presence of analytes and enables quantitative estimation of the analyte levels. We present a set of application scenarios that demonstrate the versatility of our approach and discuss the sustainability aspects, its limitations, and the implications for bio-chemical systems in HCI.

The key assumption attributed to on-body touch input is that the skin being touched provides natural tactile feedback. In this paper, we for the first time systematically explore augmenting on-body touch input with computer-generated tactile feedback. We employ vibrotactile actuation on the fingernail to couple on-body touch input with tactile feedback. Results from our first experiment show that users prefer tactile feedback for on-body touch input. In our second experiment, we determine the frequency thresholds for rendering realistic tactile “click” sensations for on-body touch buttons on three different body locations. Finally, in our third experiment, we dig deeper to render highly expressive tactile effects with a single actuator. Our non-metric multi-dimensional analysis shows that haptic augmentation of on-body buttons enhances the expressivity of on-body touch input. Overall, results from our experiments reinforce the need for tactile feedback for on-body touch input and show that actuation on the fingernail is a promising approach.

The tongue is a remarkable human organ with a high concentration of taste receptors and an exceptional ability to sense touch. This work uses electro-tactile stimulation to explore the intricate interplay between tactile perception and taste rendering on the tongue. To facilitate this exploration, we utilized a flexible, high-resolution electro-tactile prototyping platform that can be administered in the mouth. We have created a design tool that abstracts users from the low-level stimulation parameters, enabling them to focus on higher-level design objectives. Through this platform, we present the results of three studies. Our first study evaluates the design tool’s qualitative and formative aspects. In contrast, the second study measures the qualitative attributes of the sensations produced by our device, including tactile sensations and taste. In the third study, we demonstrate the ability of our device to sense touch input through the tongue when placed on the hard palate region in the mouth. Finally, we present a range of application demonstrators that span diverse domains, including accessibility, medical surgeries, and extended reality. These demonstrators showcase the versatility and potential of our platform, highlighting its ability to enable researchers and practitioners to explore new ways of leveraging the tongue’s unique capabilities. Overall, this work presents new opportunities to deploy tongue interfaces and has broad implications for designing interfaces that incorporate the tongue as a sensory organ.

Gestural interaction with freehands and while grasping an everyday object enables always-available input . To sense such gestures, minimal instrumentation of the user’s hand is desirable. However, the choice of an effective but minimal IMU layout remains challenging, due to the complexity of the multi-factorial space that comprises diverse finger gestures, objects, and grasps. We present SparseIMU , a rapid method for selecting minimal inertial sensor-based layouts for effective gesture recognition. Furthermore, we contribute a computational tool to guide designers with optimal sensor placement. Our approach builds on an extensive microgestures dataset that we collected with a dense network of 17 inertial measurement units (IMUs). We performed a series of analyses, including an evaluation of the entire combinatorial space for freehand and grasping microgestures (393 K layouts), and quantified the performance across different layout choices, revealing new gesture detection opportunities with IMUs. Finally, we demonstrate the versatility of our method with four scenarios.

Skin is a promising interaction medium and has been widely explored for mobile, and expressive interaction. Recent research in HCI has seen the development of Epidermal Computing Devices: ultra-thin and non-invasive devices which reside on the user’s skin, offering intimate integration with the curved surfaces of the body, while having physical and mechanical properties that are akin to skin, expanding the horizon of on-body interaction. However, with rapid technological advancements in multiple disciplines, we see a need to synthesize the main open research questions and opportunities for the HCI community to advance future research in this area. By systematically analyzing Epidermal Devices contributed in the HCI community, physical sciences research and from our experiences in designing and building Epidermal Devices, we identify opportunities and challenges for advancing research across five themes. This multi-disciplinary synthesis enables multiple research communities to facilitate progression towards more coordinated endeavors for advancing Epidermal Computing.

Designers and makers are increasingly interested in leveraging bio-based and bio-degradable ‘do-it-yourself’ (DIY) materials for sustainable prototyping. Their self-produced bioplastics possess compelling properties such as self-adhesion but have so far not been functionalized to create soft interactive devices, due to a lack of DIY techniques for the fabrication of functional electronic circuits and sensors. In this paper, we contribute a DIY approach for creating Interactive Bioplastics that is accessible to a wide audience, making use of easy-to-obtain bio-based raw materials and familiar tools. We present three types of conductive bioplastic materials and their formulation: sheets, pastes and foams. Our materials enable additive and subtractive fabrication of soft circuits and sensors. Furthermore, we demonstrate how these materials can substitute conventional prototyping materials, be combined with off-the-shelf electronics, and be fed into a sustainable material ‘life-cycle’ including disassembly, re-use, and re-melting of materials. A formal characterization of our conductors highlights that they are even on-par with commercially available carbon-based conductive pastes.

Using microgestures, prior work has successfully enabled gestural interactions while holding objects. Yet, these existing methods are prone to false activations caused by natural finger movements while holding or manipulating the object. We address this issue with SoloFinger, a novel concept that allows design of microgestures that are robust against movements that naturally occur during primary activities. Using a data-driven approach, we establish that single-finger movements are rare in everyday hand-object actions and infer a single-finger input technique resilient to false activation. We demonstrate this concept’s robustness using a white-box classifier on a pre-existing dataset comprising 36 everyday hand-object actions. Our findings validate that simple SoloFinger gestures can relieve the need for complex finger configurations or delimiting gestures and that SoloFinger is applicable to diverse hand-object actions. Finally, we demonstrate SoloFinger’s high performance on commodity hardware using random forest classifiers.

Advances in rapid prototyping platforms have made physiological sensing accessible to a wide audience. However, off-the-shelf electrodes commonly used for capturing biosignals are typically thick, non-conformal and do not support customization. We present PhysioSkin, a rapid, do-it-yourself prototyping method for fabricating custom multi-modal physiological sensors, using commercial materials and a commodity desktop inkjet printer. It realizes ultrathin skin-conformal patches (~1μm) and interactive textiles that capture sEMG, EDA and ECG signals. It further supports fabricating devices with custom levels of thickness and stretchability. We present detailed fabrication explorations on multiple substrate materials, functional inks and skin adhesive materials. Informed from the literature, we also provide design recommendations for each of the modalities. Evaluation results show that the sensor patches achieve a high signal-to-noise ratio. Example applications demonstrate the functionality and versatility of our approach for prototyping a next generation of physiological devices that intimately couple with the human body.

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.

In this paper, we propose and investigate a new text entry technique using micro thumb-tip gestures. Our technique features a miniature QWERTY keyboard residing invisibly on the first segment of the user's index finger. Text entry can be carried out using the thumb-tip to tap the tip of the index finger. The keyboard layout was optimized for eyes-free input by utilizing a spatial model reflecting the users' natural spatial awareness of key locations on the index finger. We present our approach of designing and optimizing the keyboard layout through a series of user studies and computer simulated text entry tests over 1,146,484 possibilities in the design space. The outcome is a 2×3 grid with the letters highly confining to the alphabetic and spatial arrangement of QWERTY. Our user evaluation showed that participants achieved an average text entry speed of 11.9 WPM and were able to type as fast as 13.3 WPM towards the end of the experiment.

Skin-based touch input opens up new opportunities for direct, subtle, and expressive interaction. However, existing skin-worn sensors are restricted to single-touch input and limited by a low resolution. We present the first skin overlay that can capture high-resolution multi-touch input. Our main contributions are: 1) Based on an exploration of functional materials, we present a fabrication approach for printing thin and flexible multi-touch sensors for on-skin interactions. 2) We present the first non-rectangular multi-touch sensor overlay for use on skin and introduce a design tool that generates such sensors in custom shapes and sizes. 3) To validate the feasibility and versatility of our approach, we present four application examples and empirical results from two technical evaluations. They confirm that the sensor achieves a high signal-to-noise ratio on the body under various grounding conditions and has a high spatial accuracy even when subjected to strong deformations.

The body provides many recognizable landmarks due to the underlying skeletal structure and variations in skin texture, elasticity, and color. The visual and spatial cues of such body landmarks can help in localizing on-body interfaces, guide input on the body, and allow for easy recall of mappings. Our main contribution are SkinMarks, novel skin-worn I/O devices for precisely localized input and output on fine body landmarks. SkinMarks comprise skin electronics on temporary rub-on tattoos. They conform to fine wrinkles and are compatible with strongly curved and elastic body locations. We identify five types of body landmarks and demonstrate novel interaction techniques that leverage SkinMarks' unique touch, squeeze and bend sensing with integrated visual output. Finally, we detail on the conformality and evaluate sub-millimeter electrodes for touch sensing. Taken together, SkinMarks expands the on-body interaction space to more detailed, highly curved and challenging areas on the body.

We present Flying Frustum, a 3D spatial interface that enables control of semi-autonomous UAVs (Unmanned Aerial Vehicles) using pen interaction on a physical model of the terrain, and that spatially situates the information streaming from the UAVs onto the physical model. Our interface is based on a 3D printout of the terrain, which allows the operator to enter goals and paths to the UAV by drawing them directly on the physical model. In turn, the UAV's streaming reconnaissance information is superimposed on the 3D printout as a view frustum, which is situated according to the UAV's position and orientation on the actual terrain. We argue that Flying Frustum's 3D spatially situated interaction can potentially help improve human-UAV awareness and enhance the overall situational awareness. We motivate our design approach for Flying Frustum, discuss previous related work in CSCW and HRI, present our preliminary prototype using both handheld and headset augmented reality interfaces, reflect on Flying Frustum's strengths and weaknesses, and discuss our plans for future evaluation and prototype improvements.