Peer Reviewed

We introduce Audio Personas, enabling users to “decorate” themselves with body-anchored sounds in audio augmented reality. Like outfits, makeup, and fragrances, audio personas offer an alternative yet dynamic channel to augment face-to-face interactions. For instance, one can set their audio persona as rain sounds to reflect a bad mood, bee sounds to establish personal boundaries, or a playful “woosh” sound to mimic passing by someone like a breeze. To instantiate the concept, we implemented a headphone-based prototype with multi-user tracking and audio streaming. Our preregistered in-lab study with 64 participants showed that audio personas influenced how participants formed impressions. Individuals with positive audio personas were rated as more socially attractive, more likable, and less threatening than those with negative audio personas. Our study with audio designers revealed that audio personas were preferred in public and semi-public-private spaces for managing social impressions (e.g., personality) and signaling current states (e.g., emotions).

Shape-changing displays enable real-time visualization and haptic exploration of 3D surfaces. However, many shape-changing displays are composed of individually actuated rigid bodies, which makes them both mechanically complex and unable to form smooth surfaces. In this work, we build a multi-stable curved line display inspired by physical splines. By using circular splines to initialize a discrete elastic rods simulator, we can model multiple stable shapes that fit specific boundary conditions. We then generate actuation instructions based on the circular spline initialization to drive the physical display. We demonstrate our display’s ability to create 16 shapes with 8 different boundary conditions. Our display is consistent in shape output, with an average standard deviation in height of 0.75 mm or 0.47% of the display’s maximum vertical range. We also show that our model is consistent with our display, with a mean RMSE of 6.68 mm or 3.85% of the display’s maximum vertical range for shapes we could stably simulate. We then demonstrate potential scalability by simulating a multi-segment version of the system and show the display’s ability to withstand loads during contour following in haptic exploration.

Illusory VR interaction techniques such as hand redirection work because humans use vision to adjust their motor commands during movement (e.g., reaching). Existing simulations of redirected reaching are limited, however, and have not yet incorporated important stochastic characteristics like sensorimotor noise, nor captured redirection’s effect on movement duration. In this work, we propose adapting a stochastic optimal feedback control (SOFC) model of normal reach to simulate redirection by augmenting sensory feedback at run-time. We present a summary of our simulation and validate it against user data gathered in multiple redirection conditions. We also evaluate the impacts of visual attention on the effectiveness of redirection in real users and replicate the effects in simulation. Our results show that an infinite-horizon SOFC model is able to reproduce key characteristics of redirected reaches and highlight the benefits of SOFC as a tool for simulating, evaluating, and gaining insights about redirection techniques.

Shape displays are a class of haptic devices that enable whole-hand haptic exploration of 3D surfaces. However, their scalability is limited by the mechanical complexity and high cost of traditional actuator arrays. In this paper, we propose using electroadhesive auxetic skins as a strain-limiting layer to create programmable shape change in a continuous (“formable crust”) shape display. Auxetic skins are manufactured as flexible printed circuit boards with dielectric-laminated electrodes on each auxetic unit cell (AUC), using monolithic fabrication to lower cost and assembly time. By layering multiple sheets and applying a voltage between electrodes on subsequent layers, electroadhesion locks individual AUCs, achieving a maximum in-plane stiffness variation of 7.6x with a power consumption of 50$\boldsymbol{\mu \mathrm{W}/\text{AUC}.}$We first characterize an individual AUC and compare results to a kinematic model. We then validate the ability of a 5x5 AUC array to actively modify its own axial and transverse stiffness. Finally, we demonstrate this array in a continuous shape display as a strain-limiting skin to programmatically modulate the shape output of an inflatable LDPE pouch. Integrating electroadhesion with auxetics enables new capabilities for scalable, low-profile, and low-power control of flexible robotic systems.

Researchers who build creativity support tools (CSTs) define abstractions and software representations that align with user needs to give users the power to accomplish tasks. However, these specifications also structure and limit how users can and should think, act, and express themselves. Thus, tool designers unavoidably exert power over their users by enacting a “normative ground” through their tools. Drawing on interviews with 11 creative practitioners, tool designers, and CST researchers, we offer a definition of empowerment in the context of creative practice, build a preliminary theory of how power relationships manifest in CSTs, and explain why researchers have had trouble addressing these concepts in the past. We re-examine CST literature through a lens of power and argue that mitigating power imbalances at the level of technical design requires enabling users in both vertical movement along levels of abstraction as well as horizontal movement between tools through interoperable representations. A lens of power is one possible orientation that lets us recognize the methodological shifts required towards building “artistic support tools.”

We can create Virtual Reality (VR) interactions that have no equivalent in the real world by remapping spacetime or altering users’ body representation, such as stretching the user’s virtual arm for manipulation of distant objects or scaling up the user’s avatar to enable rapid locomotion. Prior research has leveraged such approaches, what we call beyond-real techniques, to make interactions in VR more practical, efficient, ergonomic, and accessible. We present a survey categorizing prior movement-based VR interaction literature as reality-based, illusory, or beyond-real interactions. We survey relevant conferences (CHI, IEEE VR, VRST, UIST, and DIS) while focusing on selection, manipulation, locomotion, and navigation in VR. For beyond-real interactions, we describe the transformations that have been used by prior works to create novel remappings. We discuss open research questions through the lens of the human sensorimotor control system and highlight challenges that need to be addressed for effective utilization of beyond-real interactions in future VR applications, including plausibility, control, long-term adaptation, and individual differences.

We increasingly rely on up-to-date, data-driven graphs to understand our environments and make informed decisions. However, many of the methods blind and visually impaired users (BVI) rely on to access data-driven information do not convey important shape-characteristics of graphs, are not refreshable, or are prohibitively expensive. To address these limitations, we introduce two refreshable, 1-DOF audio-haptic interfaces based on haptic cues fundamental to object shape perception. Slide-tone uses finger position with sonification, and Tilt-tone uses fingerpad contact inclination with sonification to provide shape feedback to users. Through formative design workshops (n = 3) and controlled evaluations (n = 8), we found that BVI participants appreciated the additional shape information, versatility, and reinforced understanding these interfaces provide; and that task accuracy was comparable to using interactive tactile graphics or sonification alone. Our research offers insight into the benefits, limitations, and considerations for adopting these haptic cues into a data visualization context.

Reach redirection is an illusion-based virtual reality (VR) interaction technique where a user’s virtual hand is shifted during a reach in order to guide their real hand to a physical location. Prior works have not considered the underlying sensorimotor processes driving redirection. In this work, we propose adapting a sensorimotor model for goal-directed reach to obtain a model for visually-redirected reach, specifically by incorporating redirection as a sensory bias in the state estimate used by a minimum jerk motion controller. We validate and then leverage this model to develop a Model Predictive Control (MPC) approach for reach redirection, enabling the real-time generation of spatial warping according to desired optimization criteria (e.g., redirection goals) and constraints (e.g., sensory thresholds). We illustrate this approach with two example criteria – redirection to a desired point and redirection along a desired path – and compare our approach against existing techniques in a user evaluation.

Online data visualizations play an important role in informing public opinion but are often inaccessible to screen reader users. To address the need for accessible data representations on the web that provide direct, multimodal, and up-to-date access to the data, we investigate audio data narratives –which combine textual descriptions and sonification (the mapping of data to non-speech sounds). We conduct two co-design workshops with screen reader users to define design principles that guide the structure, content, and duration of a data narrative. Based on these principles and relevant auditory processing characteristics, we propose a dynamic programming approach to automatically generate an audio data narrative from a given dataset. We evaluate our approach with 16 screen reader users. Findings show with audio narratives, users gain significantly more insights from the data. Users describe data narratives help them better extract and comprehend the information in both the sonification and description.

Simulation offers many advantages when designing analog circuits. Designers can explore alternatives quickly, without added cost or risk of hardware faults. However, it is challenging to use simulation as an aid during interactive debugging of physical circuits, due to difficulties in comparing simulated analyses with hardware measurements. Designers must continually configure simulations to match the state of the physical circuit (e.g. capturing sensor inputs), and must manually rework the hardware to replicate changes or analyses performed in simulation. We propose techniques leveraging instrumentation and programmable test hardware to create a tight coupling between a physical circuit and its simulated model. Bridging these representations helps designers to compare simulated and measured behaviors, and to quickly perform analytical techniques on hardware (e.g. parameter-response analysis) that are typically cumbersome outside of simulation. We implement these techniques in a prototype and show how it aids in efficiently debugging a variety of analog circuits.

Modular soft robots combine the strengths of two traditionally separate areas of robotics. As modular robots, they can show robustness to individual failure and reconfigurability; as soft robots, they can deform and undergo large shape changes in order to adapt to their environment, and have inherent human safety. However, for sensing and communication these robots also combine the challenges of both: they require solutions that are scalable (low cost and complexity) and efficient (low power) to enable collectives of large numbers of robots, and these solutions must also be able to interface with the high extension ratio elastic bodies of soft robots. In this work, we seek to address these challenges using acoustic signals produced by piezoelectric surface transducers that are cheap, simple, and low power, and that not only integrate with but also leverage the elastic robot skins for signal transmission. Importantly, to further increase scalability, the transducers exhibit multi-functionality made possible by a relatively flat frequency response across the audible and ultrasonic ranges. With minimal hardware, they enable directional contact-based communication, audible-range communication at a distance, and exteroceptive sensing. We demonstrate a subset of the decentralized collective behaviors that these functions make possible with multi-robot hardware implementations. The use of acoustic waves in this domain is shown to provide distinct advantages over existing solutions.

Soft isoperimetric truss robots have demonstrated an ability to grasp and manipulate objects using the members of their structure. The compliance of the members affords large contact areas with even force distribution, allowing for successful grasping even with imprecise open-loop control. In this work we present methods of analyzing and controlling isoperimetric truss robots in the context of grasping and manipulating objects. We use a direct stiffness model to characterize the structural properties of the robot and its interactions with external objects. With this approach we can estimate grasp forces and stiffnesses with limited computation compared to higher fidelity finite elements methods, which, given the many degrees-of-freedom of truss robots, are prohibitively expensive to run on-board. In conjunction with the structural model, we build upon a literature of differential kinematics for truss robots and apply it to the task of manipulating an object within the robot’s workspace.

This paper introduces a new class of soft reconfigurable robot: balloon animal robots. The balloon animal robot consists of a closed volume inflatable tube which can be reconfigured into structures of varying topology by a collective of simple sub-unit robots. The robotic sub-units can (1) drive along the length of the tube to localize a joint, (2) create pinch points that locally reduce the bending stiffness of the tube to form a joint, and (3) selectively mechanically couple to one another through cable driven actuators to create nodes of the structure. In this work we introduce the hardware necessary to construct the robot, present experiments to guide the hardware design, and formulate an algorithm using graph theory to calculate the number of nodes and node connections needed to form different 2D shapes. Finally, we demonstrate the system with two active nodes and four passive nodes forming multiple 2D shapes from the same hardware.

Mix-and-match character creation tools enable users to quickly produce 2D character illustrations by combining various predefined accessories, like clothes and hairstyles, which are represented as separate, interchangeable artwork layers. However, these accessory layers are often designed to fit only the default body artwork, so users cannot modify the body without manually updating all the accessory layers as well. To address this issue, we present a method that captures and preserves important relationships between artwork layers so that the predefined accessories adapt with the character’s body. We encode these relationships with four types of constraints that handle common interactions between layers: (1) occlusion, (2) attachment at a point, (3) coincident boundaries, and (4) overlapping regions. A rig is a set of constraints that allow a motion or deformation specified on the body to transfer to the accessory layers. We present an automated algorithm for generating such a rig for each accessory layer, but also allow users to select which constraints to apply to specific accessories. We demonstrate how our system supports a variety of modifications to body shape and pose using artwork from mix-and-match data sets.

As swarm robots begin to share the same space with people, it is critical to design legible swarm robot motion that clearly and rapidly communicates the intent of the robots to nearby users. To address this, we apply concepts from intent-expressive robotics, swarm intelligence, and vision science. Specifically, we leverage the trajectory, collective behavior, and density of swarm robots to generate motion that implicitly guides people’s attention toward the goal of the robots. Through online evaluations, we compared different types of intent-expressive motions both in terms of legibility as well as glanceability, a measure we introduce to gauge an observer’s ability to predict robots’ intent pre-attentively. The results show that the collective behavior-based motion has the best legibility performance overall, whereas, for glanceability, trajectory-based legible motion is most effective. These results suggest that the optimal solution may involve a combination of these legibility cues based on the scenario and the desired properties of the motion.

In this article, we investigate the effects of active transient vibration and visuo-haptic illusion to augment the perceived softness of haptic proxy objects. We introduce a system combining active transient vibration at the fingertip with visuo-haptic illusions. In our hand-held device, a voice coil actuator transmits active transient vibrations to the index fingertip, while a force sensor measures the force applied on passive proxy objects to create visuo-haptic illusions in virtual reality. We conducted three user studies to understand both the vibrotactile effect and its combined effect with visuo-haptic illusions. A preliminary study confirmed that active transient vibrations can intuitively alter the perceived softness of a proxy object. Our first study demonstrated that those same active transient vibrations can generate different perceptions of softness depending on the material of the proxy object used. In our second study, we evaluated the combination of active transient vibration and visuo-haptic illusion, and found that both significantly influence perceived softness, with with the visuo-haptic effect being dominant. Our third study further investigated the vibrotactile effect while controlling for the visuo-haptic illusion. The combination of these two methods allows users to effectively perceive various levels of softness when interacting with haptic proxy objects.

The ability to effectively read and interpret tactile graphics and charts is an essential part of a tactile learner’s path to literacy, but is a skill that requires instruction and training. Many teachers of the visual impaired (TVIs) report that blind and visually impaired students have trouble interpreting graphics independently without individual instruction. We present PantoGuide, a low-cost system that provides audio and haptic guidance, via skin-stretch feedback to the dorsum of a user’s hand while the user explores a tactile graphic overlaid on a touchscreen. This system allows programming of haptic guidance patterns and cues for tactile graphics that can be experienced by students learning remotely or that can be reviewed by a student independently. We propose two teaching scenarios (synchronous and asynchronous) and two guidance interactions (point-to-point and continuous) that the device can support – and demonstrate their use in a set of applications we co-design with one co-author who is blind and a tactile graphics user.

As data visualization has become increasingly important in our society, many challenges prevent people who are blind and visually impaired (BVI) from fully engaging with data and data graphics. For example, tactile data representations are commonly used by BVI people to explore spatial graphics, but it is difficult for BVI people to construct and understand tactile representations without prior training or expert assistance. In this work, we adopt a constructive visualization framework of using simple and versatile tokens to engage non-experts in the construction of tactile data representations. We present preliminary results of how participants chose to interpret and create tactile data representations and the preferred haptic exploratory procedures used for retrieving information. All participants used similar construction strategies and converged upon 3D compact spatial forms to retrieve and display analytical information. These insights can inform future data visualization authoring and consumption tools that users of more diverse skill backgrounds can effectively navigate.

A swarm of robots can accomplish more than the sum of its parts, and swarm systems will soon see increased use in applications ranging from tangible interfaces to search and rescue teams. However, effective human control of robot swarms has been shown to be demonstrably more difficult than controlling a single robot, and swarm-specific interactions methodologies are relatively underexplored. As we envision even non-expert users will have more daily in-person encounters with different numbers of robots in the future, we present a user-defined set of control interactions for tabletop swarm robots derived from an elicitation study. We investigated the effects of number of robots and proximity on the user's interaction and found significant effects. For instance, participants varied between using 1-2 fingers, one hand, and both hands depending on the group size. We also provide general design guidelines such as preferred interaction modality, common strategies, and a high-agreement interaction set.

Introducing interactive components into furniture has proven difficult due to the different lifespans of furniture and digital devices. We present Foxels, a modular, smart furniture concept that allows users to create their own interactive furniture on demand by simply snapping together individual building blocks. The modular design makes the system flexible to accommodate a variety of interactive furniture setups, making it particularly well-suited for re-configurable spaces. Considering the trade-off between ease-of-use and high versatility, we explored a number of interaction methods that can be applied to modular interactive furniture, thereby extending the well-known tangible programming paradigm. After explaining our implementation, we demonstrate the validity of the proposed concepts by presenting how Foxels can be used in an ideation workshop along with many additional real-world examples.

Encountered-type haptic devices (EHDs) face a number of challenges when physically embodying content in a virtual environment, including workspace limits and device latency. To address these issues, we propose REACH+, a framework for dynamic visuo-haptic redirection to improve the perceived performance of EHDs during physical interaction in VR. Using this approach, we estimate the user's arrival time to their intended target and redirect their hand to a point within the EHD's spatio-temporally reachable space. We present an evaluation of this framework implemented with a desktop mobile robot in a 2D target selection task, tested at four robot speeds (20, 25, 30 and 35 cm/s). Results suggest that REACH+ can improve the performance of lower-speed EHDs, increasing their rate of on-time arrival to the point of contact by up to 25% and improving users? self-reported sense of realism.

Humans can perceive motion through a variety of different modalities. Vision is a well explored modality; however haptics can greatly increase the richness of information provided to the user. The detailed differences in perception of motion between these two modalities are not well studied and can provide an additional avenue for communication between humans and haptic devices or robots. We analyze these differences in the context of users interactions with a non-anthropomorphic haptic device. In this study, participants experienced different levels and combinations of stiffness, jitter, and acceleration curves via a one degree of freedom linear motion display. These conditions were presented with and without the opportunity for users to touch the setup. Participants rated the experiences within the contexts of emotion, anthropomorphism, likeability, and safety using the SAM scale, HRI metrics, as well as with qualitative feedback. A positive correlation between stiffness and dominance, specifically due to the haptic condition, was found; additionally, with the introduction of jitter, decreases in perceived arousal and likeability were recorded. Trends relating acceleration curves to perceived dominance as well as stiffness and jitter to valence, arousal, dominance, likeability, and safety were also found. These results suggest the importance of considering which sensory modalities are more actively engaged during interactions and, concomitantly, which behaviors designers should employ in the creation of non-anthropomorphic interactive haptic devices to achieve a particular interpreted affective state.

Skimming new code with a screen reader can be a time-consuming task for blind and visually impaired programmers. Screen readers aid with code navigation, but dictate code line-by-line and read spaces and tabs individually. This often provides more information than is needed. In this work, we present the Tactile Code Skimmer (TCS), a tool to aid blind and visually impaired programmers with skimming code. The device physically reflects the indentation levels of code with actuated slide potentiometers, thus helping reduce the "hearing load" that often accompanies screen readers. We describe the TCS design and implementation. Based on feedback from participants obtained through demos and an in-depth session, we discuss some considerations for tactile tools that aid with code skimming.

Affordable rapid 3D printing technologies have become key enablers of the Maker Movement by giving individuals the ability to create physical finished products. However, existing computer-aided design (CAD) tools that allow authoring and editing of 3D models are mostly visually reliant and limit access to people with blindness and visual impairment (BVI). Through a series of co-design sessions with three blind users of mixed programming ability, we identify accessibility challenges in existing 3D modelling scripting tools and design interactions to support dynamic feedback of scripts using a 2.5D tactile shape display. With these insights, we implement shapeCAD. Interacting with shapeCAD, BVI users are able to leverage the low resolution output from a 2.5D shape display to complement programming of 3D models. shapeCAD allows users to haptically explore and modify existing models, and to author new models. We further validate usability and user experience through an evaluation with five BVI programmers. In a short period of time, novices were able to design a range of new objects. BVI users can bring a valuable perspective to design and it is imperative to increase accessibility in tools that enable this community to also participate as designers.

Quadcopters have been used as hovering encountered-type haptic devices in virtual reality. We suggest that quadcopters can facilitate rich haptic interactions beyond force feedback by appropriating physical objects and the environment. We present HoverHaptics, an autonomous safe-to-touch quadcopter and its integration with a virtual shopping experience. HoverHaptics highlights three affordances of quadcopters that enable these rich haptic interactions: (1) dynamic positioning of passive haptics, (2) texture mapping, and (3) animating passive props. We identify inherent challenges of hovering encountered-type haptic devices, such as their limited speed, inadequate control accuracy, and safety concerns. We then detail our approach for tackling these challenges, including the use of display techniques, visuo-haptic illusions, and collision avoidance. We conclude by describing a preliminary study (n = 9) to better understand the subjective user experience when interacting with a quadcopter in virtual reality using these techniques.

This paper seeks to better understand the use of haptic feedback in abstract, ubiquitous robotic interfaces. We introduce and provide preliminary evaluations of SwarmHaptics, a new type of haptic display using a swarm of small, wheeled robots. These robots move on a flat surface and apply haptic patterns to the user's hand, arm, or any other accessible body parts. We explore the design space of SwarmHaptics including individual and collective robot parameters, and demonstrate example scenarios including remote social touch using the Zooids platform. To gain insights into human perception, we applied haptic patterns with varying number of robots, force type, frequency, and amplitude and obtained user's perception in terms of emotion, urgency, and Human-Robot Interaction metrics. In a separate elicitation study, users generated a set of haptic patterns for social touch. The results from the two studies help inform how users perceive and generate haptic patterns with SwarmHaptics.

Spatial layout is a key component in graphic design. While people who are blind or visually impaired (BVI) can use screen readers or magnifiers to access digital content, these tools fail to fully communicate the content's graphic design information. Through semi-structured interviews and contextual inquiries, we identify the lack of this information and feedback as major challenges in understanding and editing layouts. Guided by these insights and a co-design process with a blind hobbyist web developer, we developed an interactive, multimodal authoring tool that lets blind people understand spatial relationships between elements and modify layout templates. Our tool automatically generates tactile print-outs of a web page's layout, which users overlay on top of a tablet that runs our self-voicing digital design tool. We conclude with design considerations grounded in user feedback for improving the accessibility of spatially encoded information and developing tools for BVI authors.

Difficulties in accessing, isolating, and iterating on the components and connections of a printed circuit board (PCB) create unique challenges in PCB debugging. Manual probing methods are slow and error prone, and even dedicated PCB testing equipment remains limited by its inability to modify the circuit during testing. We present Pinpoint, a tool that facilitates in-circuit PCB debugging through techniques such as programmatically probing signals, dynamically disconnecting components and subcircuits to test in isolation, and splicing in new elements to explore potential modifications. Pinpoint automatically instruments a PCB design and generates designs for a physical jig board that interfaces the user's PCB to our custom testing hardware and to software tools. We evaluate Pinpoint's ability to facilitate the debugging of various PCB issues by instrumenting and testing different classes of boards, as well as by characterizing its technical limitations and by soliciting feedback through a guided exploration with PCB designers.

Haptic retargeting is a virtual reality (VR) interaction technique enabling virtual objects to be ”remapped” to different haptic proxies by offsetting the user’s virtual hand from their physical hand. While researchers have investigated single-hand retargeting, the effects of bimanual interaction in the context of haptic retargeting have been less explored. In this study, we present an evaluation of perceptual detection rates for bimanual haptic retargeting in VR. We tested 64 combinations of simultaneous left- and right-hand retargeting ranging from − 24° to + 24° offsets and found that bimanual retargeting can be more noticeable to users when the hands are redirected in different directions as opposed to the same direction.

This paper introduces dynamic composite physicalizations, a new class of physical visualizations that use collections of self-propelled objects to represent data. Dynamic composite physicalizations can be used both to give physical form to well-known interactive visualization techniques, and to explore new visualizations and interaction paradigms. We first propose a design space characterizing composite physicalizations based on previous work in the fields of Information Visualization and Human Computer Interaction. We illustrate dynamic composite physicalizations in two scenarios demonstrating potential benefits for collaboration and decision making, as well as new opportunities for physical interaction. We then describe our implementation using wheeled micro-robots capable of locating themselves and sensing user input, before discussing limitations and opportunities for future work.

Affordable rapid 3D printing technologies have become a key enabler in the maker movement by giving individuals the ability to create physical finished products. However, existing computer-aided design (CAD) tools that allow authoring and editing of 3D models are mostly visually reliant and limit access for people who are blind or visually impaired. We propose an accessible CAD workflow where 3D models are generated through OpenSCAD, a script-based 3D modeling tool, and rendered at interactive speeds in an actuated 2.5D shape display. We report preliminary findings on a case study with one blind user. Based on our observations, we frame design imperatives on interactions that might be important in future accessible CAD systems with tactile output.

In this work, we utilize visuo-haptic illusions to improve the perceived performance of encountered-type haptic devices, specifically shape displays, in virtual reality. Shape displays are matrices of actuated pins that travel vertically to render physical shapes; however, they have limitations such as low resolution, small display size, and low pin speed. To address these limitations, we employ illusions such as redirection, scaling, and retargeting that take advantage of the visual dominance effect, the idea that vision often dominates when senses conflict. Our evaluation of these techniques suggests that redirecting sloped lines with angles less than 40 degrees onto a horizontal line is an effective technique for increasing the perceived resolution of the display. Scaling up the virtual object onto the shape display by a factor less than 1.8x can also increase the perceived resolution. Finally, using vertical redirection a perceived 3x speed increase can be achieved.

Shape-changing interfaces have emerged as a new method for interacting with computers, using dynamic changes in a device's physical shape for input and output. With the advances of research into shape-changing interfaces, we see a need to synthesize the main, open research questions. The purpose of this synthesis is to formulate common challenges across the diverse fields engaged in shape-change research, to facilitate progression from single prototypes and individual design explorations to grander scientific goals, and to draw attention to challenges that come with maturity, including those concerning ethics, theory-building, and societal impact. In this article we therefore present 12 grand challenges for research on shape-changing interfaces, derived from a three-day workshop with 25 shape-changing interface experts with backgrounds in design, computer science, human-computer interaction, engineering, robotics, and material science.

We explore interactions enabled by 2D spatial manipulation and self-actuation of a tabletop shape display. To explore these interactions, we developed shapeShift, a compact, high-resolution (7 mm pitch), mobile tabletop shape display. shapeShift can be mounted on passive rollers allowing for bimanual interaction where the user can freely manipulate the system while it renders spatially relevant content. shapeShift can also be mounted on an omnidirectional-robot to provide both vertical and lateral kinesthetic feedback, display moving objects, or act as an encountered-type haptic device for VR. We present a study on haptic search tasks comparing spatial manipulation of a shape display for egocentric exploration of a map versus exploration using a fixed display and a touch pad. Results show a 30% decrease in navigation path lengths, 24% decrease in task time, 15% decrease in mental demand and 29% decrease in frustration in favor of egocentric navigation.

Passive or actuated physical props can provide haptic feedback, leading to a satisfying sense of presence and realism in virtual reality. However, the mismatch between the physical and virtual surfaces (boundaries) can diminish user experience. Haptic retargeting can overcome this limitation by utilizing visio-haptic effects. Previous investigations in haptic retargeting have focused on methods for point based position retargeting and techniques for remapping 2D shapes or simple 3D shape changes. Our approach extends haptic retargeting to complex, arbitrary shapes that provide a continuous mapping across all points on a boundary. This new approach also allows for multi-finger interaction. We describe a functional optimization to find the ideal spatial warping function with different goals: a maximum mapping smoothness, a minimum mismatch between the real and virtual world, or the combination of the two. We report on a preliminary user study of different optimization goals and elaborate potential applications through a set of demonstrations.

Jewelry and accessories have long been objects for decorating the human body; however they remain static and non-interactive. This work explores opportunities for accessory-like kinetic wearables and their association with individual style. We developed Kino, a kinetic accessory system which enables both aesthetic and functional clothing-specific design possibilities. We engaged both fashion designers and every-day users to unpack envisioned use cases and perceptions of the system. Participants viewed the devices not as gadgets but as companions due to their close proximity to the body. They envisioned a wide range of usage scenarios, highlighting the complexity of mobility in relation to personal style. We observe how mobility offers opportunities for fluid representations of self, which is unachievable though static clothing and accessories. We also outline how personalized aesthetics is important for the meaning making of novel on-body devices.

We present a first prototype of an open-ended interactive physical game aiming at developing children's understanding of dynamic systems in a playful and embodied way. We use a swarm user interface, Zooids, developed by Le Goc et al., made of independent self-propelled elements that move collectively and react to user input. Papert promoted an active way of developing a computational literacy, through programming a turtle with LOGO, from which Resnick proposed StarLogo, a "multi-turtles" language to simulate complex systems behaviors. Our interface is positioned in between these two perspectives: it allows to physically interact with multiple "turtles", each having its own dynamic. Each Zooid can be assigned an action that will affect the system behavior. Based on this principle, our first prototype invites children to resolve situations by changing individual actions in a dynamic system.

Currently, virtual (i.e. touchscreen) controls are dynamic, but lack the advantageous tactile feedback of physical controls. Similarly, devices may also have dedicated physical controls, but they lack the flexibility to adapt for different contexts and applications. On mobile and wearable devices in particular, space constraints further limit our input and output capabilities. We propose utilizing reconfigurable tactile elements around the edge of a mobile device to enable dynamic physical controls and feedback. These tactile elements can be used for physical touch input and output, and can reposition according to the application both around the edge of and hidden within the device. We present shiftIO, two implementations of such a system which actuate physical controls around the edge of a mobile device using magnetic locomotion. One version utilizes PCB-manufactured electromagnetic coils, and the other uses switchable permanent magnets. We perform a technical evaluation of these prototypes and compare their advantages in various applications. Finally, we demonstrate several mobile applications which leverage shiftIO to create novel mobile interactions.

We present the design, modeling, and implementation of a novel pneumatic actuator, the Pneumatic Reel Actuator (PRA). The PRA is highly extensible, lightweight, capable of operating in compression and tension, compliant, and inexpensive. An initial prototype of the PRA can reach extension ratios greater than 16:1, has a force-to-weight ratio over 28:1, reach speeds of 0.87 meters per second, and can be constructed with parts totaling less than $4 USD. We have developed a model describing the actuator and have conducted experiments characterizing the actuator's performance in regards to force, extension, pressure, and speed. We have implemented two parallel robotic applications in the form of a three degree of freedom robot arm and a tetrahedral robot.

We consider a class of robotic systems composed of high elongation linear actuators connected at universal joints. We derive the differential kinematics of such robots, and formalize concepts of controllability based on graph rigidity. Control methods are then developed for two separate applications: locomotion and shape morphing. The control algorithm in both cases solves a series of linearly constrained quadratic programs at each time step to minimize an objective function while ensuring physical feasibility. We present simulation results for locomotion along a prescribed path, and morphing to a target shape.

Passive haptic proxy objects allow for rich tangible interaction, and this is especially true in VR applications. However, this requires users to have many physical objects at hand. Our paper proposes robotic assembly at run-time of low-resolution haptic proxies for tangible interaction and virtual reality. These assembled physical proxy objects are composed of magnetically attached blocks which are assembled by a small multi robot system, specifically Zooids. We explore the design of the basic building blocks and illustrate two approaches to assembling physical proxies: using multirobot systems to (1) self-assemble into structures and (2) assemble 2.5D structure with passive blocks of various heights. The success rate and completion time are evaluated for both approaches. Finally, we demonstrate the potential of assembled proxy objects for tangible interaction and virtual reality through a set of demonstrations.

Ungrounded haptic devices for virtual reality (VR) applications lack the ability to convincingly render the sensations of a grasped virtual object's rigidity and weight. We present Grabity, a wearable haptic device designed to simulate kinesthetic pad opposition grip forces and weight for grasping virtual objects in VR. The device is mounted on the index finger and thumb and enables precision grasps with a wide range of motion. A unidirectional brake creates rigid grasping force feedback. Two voice coil actuators create virtual force tangential to each finger pad through asymmetric skin deformation. These forces can be perceived as gravitational and inertial forces of virtual objects. The rotational orientation of the voice coil actuators is passively aligned with the real direction of gravity through a revolute joint, causing the virtual forces to always point downward. This paper evaluates the performance of Grabity through two user studies, finding promising ability to simulate different levels of weight with convincing object rigidity. The first user study shows that Grabity can convey various magnitudes of weight and force sensations to users by manipulating the amplitude of the asymmetric vibration. The second user study shows that users can differentiate different weights in a virtual environment using Grabity.

Analog circuit design is a complex, error-prone task in which the processes of gathering observations, formulating reasonable hypotheses, and manually adjusting the circuit raise significant barriers to an iterative workflow. We present Scanalog, a tool built on programmable analog hardware that enables users to rapidly explore different circuit designs using direct manipulation, and receive immediate feedback on the resulting behaviors without manual assembly, calculation, or probing. Users can interactively tune modular signal transformations on hardware with real inputs, while observing real-time changes at all points in the circuit. They can create custom unit tests and assertions to detect potential issues. We describe three interactive applications demonstrating the expressive potential of Scanalog. In an informal evaluation, users successfully conditioned analog sensors and described Scanalog as both enjoyable and easy to use.

Current mobile devices do not leverage the rich haptic channel of information that our hands can sense, and instead focus primarily on touch based graphical interfaces. Our goal is to enrich the user experience of these devices through bi-directional haptic and tactile interactions (display and control) around the edge of hand-held devices. We propose a novel type of haptic interface, a Haptic Edge Display, consisting of actuated pins on the side of a display, to form a linear array of tactile pixels (taxels). These taxels are implemented using small piezoelectric actuators, which can be made cheaply and have ideal characteristics for mobile devices. We developed two prototype Haptic Edge Displays, one with 24 actuated pins (3.75mm in pitch) and a second with 40 pins (2.5mm in pitch). This paper describes several novel haptic interactions for the Haptic Edge Display including dynamic physical affordances, shape display, non-dominant hand interactions, and also in-pocket ``pull' style haptic notifications. In a laboratory experiment we investigated the limits of human perception for Haptic Edge Displays, measuring the just-noticeable difference for pin width and height changes for both in-hand and simulated in-pocket conditions.

Shape changing interfaces give physical shapes to digital data so that users can feel and manipulate data with their hands and bodies. However, physical objects in our daily life not only have shape but also various material properties. In this paper, we propose an interaction technique to represent material properties using shape changing interfaces. Specifically, by integrating the multi-modal sensation techniques of haptics, our approach builds a perceptive model for the properties of deformable materials in response to direct manipulation. As a proof-of-concept prototype, we developed preliminary physics algorithms running on pin-based shape displays. The system can create computationally variable properties of deformable materials that are visually and physically perceivable. In our experiments, users identify three deformable material properties (flexibility, elasticity and viscosity) through direct touch interaction with the shape display and its dynamic movements. In this paper, we describe interaction techniques, our implementation, future applications and evaluation on how users differentiate between specific properties of our system. Our research shows that shape changing interfaces can go beyond simply displaying shape allowing for rich embodied interaction and perceptions of rendered materials with the hands and body.

The Wolverine is a mobile, wearable haptic device designed for simulating the grasping of rigid objects in a virtual reality interface. In contrast to prior work on wearable force feedback gloves, we focus on creating a low cost and lightweight device that renders a force directly between the thumb and three fingers to simulate objects held in pad opposition (precision) type grasps. Leveraging low-power brake-based locking sliders, the system can withstand over 100N of force between each finger and the thumb, and only consumes 0.24 mWh (0.87 joules) for each braking interaction. Integrated sensors are used both for feedback control and user input: time-of-flight sensors provide the position of each finger and an IMU provides overall orientation tracking. This paper describes the mechanical design, control strategy, and performance analysis of the Wolverine system and provides a comparison with several existing wearable haptic devices.

We introduce Rovables, a miniature robot that can move freely on unmodified clothing. The robots are held in place by magnetic wheels, and can climb vertically. The robots are untethered and have an onboard battery, microcontroller, and wireless communications. They also contain a low-power localization system that uses wheel encoders and IMU, allowing Rovables to perform limited autonomous navigation on the body. In the technical evaluations, we found that Rovables can operate continuously for 45 minutes and can carry up to 1.5N. We propose an interaction space for mobile on-body devices spanning sensing, actuation, and interfaces, and develop application scenarios in that space. Our applications include on-body sensing, modular displays, tactile feedback and interactive clothing and jewelry.

This paper introduces swarm user interfaces, a new class of human-computer interfaces comprised of many autonomous robots that handle both display and interaction. We describe the design of Zooids, an open-source open-hardware platform for developing tabletop swarm interfaces. The platform consists of a collection of custom-designed wheeled micro robots each 2.6 cm in diameter, a radio base-station, a high-speed DLP structured light projector for optical tracking, and a software framework for application development and control. We illustrate the potential of tabletop swarm user interfaces through a set of application scenarios developed with Zooids, and discuss general design considerations unique to swarm user interfaces.

This paper presents ChainFORM: a linear, modular, actuated hardware system as a novel type of shape changing interface. Using rich sensing and actuation capability, this modular hardware system allows users to construct and customize a wide range of interactive applications. Inspired by modular and serpentine robotics, our prototype comprises identical modules that connect in a chain. Modules are equipped with rich input and output capability: touch detection on multiple surfaces, angular detection, visual output, and motor actuation. Each module includes a servo motor wrapped with a flexible circuit board with an embedded microcontroller.

In this paper we explore the design space of actuated curve interfaces, a novel class of shape changing-interfaces. Physical curves have several interesting characteristics from the perspective of interaction design: they have a variety of inherent affordances; they can easily represent abstract data; and they can act as constraints, boundaries, or borderlines. By utilizing such aspects of lines and curves, together with the added capability of shape-change, new possibilities for display, interaction and body constraint are possible. In order to investigate these possibilities we have implemented two actuated curve interfaces at different scales. LineFORM, our implementation, inspired by serpentine robotics, is comprised of a series chain of 1DOF servo motors with integrated sensors for direct manipulation. To motivate this work we present various applications such as shape changing cords, mobiles, body constraints, and data manipulation tools.

To fabricate functional objects, designers create assemblies combining existing parts (e.g., mechanical hinges, electronic components) with custom-designed geometry (e.g., enclosures). Modeling complex assemblies is outside the reach of the growing number of novice ``makers' with access to digital fabrication tools. We aim to allow makers to design and 3D print functional mechanical and electronic assemblies. Based on a formative exploration, we created Makers' Marks, a system based on physically authoring assemblies with sculpting materials and annotation stickers. Makers physically sculpt the shape of an object and attach stickers to place existing parts or high-level features (such as parting lines). Our tool extracts the 3D pose of these annotations from a scan of the design, then synthesizes the geometry needed to support integrating desired parts using a library of clearance and mounting constraints. The resulting designs can then be easily 3D printed and assembled. Our approach enables easy creation of complex objects such as TUIs, and leverages physical materials for tangible manipulation and understanding scale. We validate our tool through several design examples: a custom game controller, an animated toy figure, a friendly baby monitor, and a hinged box with integrated alarm.

Pin-based shape displays not only give physical form to digital information, they have the inherent ability to accurately move and manipulate objects placed on top of them. In this paper we focus on such object manipulation: we present ideas and techniques that use the underlying shape change to give kinetic ability to otherwise inanimate objects. First, we describe the shape display's ability to assemble, disassemble, and reassemble structures from simple passive building blocks through stacking, scaffolding, and catapulting. A technical evaluation demonstrates the reliability of the presented techniques. Second, we introduce special kinematic blocks that are actuated and sensed through the underlying pins. These blocks translate vertical pin movements into other degrees of freedom like rotation or horizontal movement. This interplay of the shape display with objects on its surface allows us to render otherwise inaccessible forms, like overhangs, and enables richer input and output.

We propose a new approach to Physical Telepresence, based on shared workspaces with the ability to capture and remotely render the shapes of people and objects. In this paper, we describe the concept of shape transmission, and propose interaction techniques to manipulate remote physical objects and physical renderings of shared digital content. We investigate how the representation of user's body parts can be altered to amplify their capabilities for teleoperation. We also describe the details of building and testing prototype Physical Telepresence workspaces based on shape displays. A preliminary evaluation shows how users are able to manipulate remote objects, and we report on our observations of several different manipulation techniques that highlight the expressive nature of our system.

Recent research in 3D user interfaces pushes towards immersive graphics and actuated shape displays. Our work explores the hybrid of these directions, and we introduce sublimation and deposition, as metaphors for the transitions between physical and virtual states. We discuss how digital models, handles and controls can be interacted with as virtual 3D graphics or dynamic physical shapes, and how user interfaces can rapidly and fluidly switch between those representations. To explore this space, we developed two systems that integrate actuated shape displays and augmented reality (AR) for co-located physical shapes and 3D graphics. Our spatial optical see-through display provides a single user with head-tracked stereoscopic augmentation, whereas our handheld devices enable multi-user interaction through video seethrough AR. We describe interaction techniques and applications that explore 3D interaction for these new modalities. We conclude by discussing the results from a user study that show how freehand interaction with physical shape displays and co-located graphics can outperform wand-based interaction with virtual 3D graphics.

Past research on shape displays has primarily focused on rendering content and user interface elements through shape output, with less emphasis on dynamically changing UIs. We propose utilizing shape displays in three different ways to mediate interaction: to facilitate by providing dynamic physical affordances through shape change, to restrict by guiding users with dynamic physical constraints, and to manipulate by actuating physical objects. We outline potential interaction techniques and introduce Dynamic Physical Affordances and Constraints with our inFORM system, built on top of a state-of-the-art shape display, which provides for variable stiffness rendering and real-time user input through direct touch and tangible interaction. A set of motivating examples demonstrates how dynamic affordances, constraints and object actuation can create novel interaction possibilities.

This paper presents PneUI, an enabling technology to build shape-changing interfaces through pneumatically-actuated soft composite materials. The composite materials integrate the capabilities of both input sensing and active shape output. This is enabled by the composites' multi-layer structures with different mechanical or electrical properties. The shape changing states are computationally controllable through pneumatics and pre-defined structure. We explore the design space of PneUI through four applications: height changing tangible phicons, a shape changing mobile, a transformable tablet case and a shape shifting lamp.

Children have great facility in the physical world, and can skillfully model in clay and draw expressive illustrations. Traditional digital modeling tools have focused on mouse, keyboard and stylus input. These tools may be complicated and difficult for young users to easily and quickly create exciting designs. We seek to bring physical interaction to digital modeling, to allow users to use existing physical objects as tangible building blocks for new designs. We introduce KidCAD a digital clay interface for children to remix toys. KidCAD allows children to imprint 2.5D shapes from physical objects into their digital models by deforming a malleable gel input device, deForm. Users can mashup existing objects, edit and sculpt or draw new designs on a 2.5D canvas using physical objects, hands and tools as well as 2D touch gestures. We report on a preliminary user study with 13 children, ages 7 to 10, which provides feedback for our design and helps guide future work in tangible modeling for children.

We introduce People in Books with FlashCam technology, a system that supports children and long-distance family members to act as characters in children's storybooks while they read stories together over a distance. By segmenting the video chat streams of the child and remote family member from their background surroundings, we create the illusion that the child and adult reader are immersed among the storybook illustrations. The illusion of inhabiting a shared story environment helps remote family members feel a sense of togetherness and encourages active reading behaviors for children ages three to five. People In Books is designed to fit into families' traditional reading practices, such as reading ebooks on couches or in bed via netbook or tablet computers. To accommodate this goal we implemented FlashCam, a computationally cost effective and physically small background subtraction system for mobile devices that allows users to move locations and change lighting conditions while they engage in background-subtracted video communications. A lab evaluation compared People in Books with a conventional remote reading application. Results show that People in Books motivates parents and children to be more performative readers and encourages open-ended play beyond the story, while creating a strong sense of togetherness.

Malleable and organic user interfaces have the potential to enable radically new forms of interactions and expressiveness through flexible, free-form and computationally controlled shapes and displays. This work, specifically focuses on particle jamming as a simple, effective method for flexible, shape-changing user interfaces where programmatic control of material stiffness enables haptic feedback, deformation, tunable affordances and control gain. We introduce a compact, low-power pneumatic jamming system suitable for mobile devices, and a new hydraulic-based technique with fast, silent actuation and optical shape sensing. We enable jamming structures to sense input and function as interaction devices through two contributed methods for high-resolution shape sensing using: 1) index-matched particles and fluids, and 2) capacitive and electric field sensing. We explore the design space of malleable and organic user interfaces enabled by jamming through four motivational prototypes that highlight jamming's potential in HCI, including applications for tabletops, tablets and for portable shape-changing mobile devices.

We introduce a novel input device, deForm, that supports 2.5D touch gestures, tangible tools, and arbitrary objects through real-time structured light scanning of a malleable surface of interaction. DeForm captures high-resolution surface deformations and 2D grey-scale textures of a gel surface through a three-phase structured light 3D scanner. This technique can be combined with IR projection to allow for invisible capture, providing the opportunity for co-located visual feedback on the deformable surface. We describe methods for tracking fingers, whole hand gestures, and arbitrary tangible tools. We outline a method for physically encoding fiducial marker information in the height map of tangible tools. In addition, we describe a novel method for distinguishing between human touch and tangible tools, through capacitive sensing on top of the input surface. Finally we motivate our device through a number of sample applications.

Long-distance families are increasingly staying connected with free video conferencing tools. However research has highlighted a need for shared activities for long-distance family communication. While video technology is reportedly superior to audio-only tools for children under age 7, the tools themselves are not designed to accommodate children's or families' needs. This paper introduces four design explorations of shared play activities over video conferencing that support family togetherness between children and remote adult family members. We build on research in CSCW and child development to create opportunities for silliness and open-ended play between adults and young children. Our goal is to scaffold interaction across distance and generations.

Interaction designers typically revise user interface prototypes by adding unstructured notes to storyboards and screen printouts. How might computational tools increase the efficacy of UI revision? This paper introduces d.note, a revision tool for user interfaces expressed as control flow diagrams. d.note introduces a command set for modifying and annotating both appearance and behavior of user interfaces; it also defines execution semantics so proposed changes can be tested immediately. The paper reports two studies that compare production and interpretation of revisions in d.note to freeform sketching on static images (the status quo). The revision production study showed that testing of ideas during the revision process led to more concrete revisions, but that the tool also affected the type and number of suggested changes. The revision interpretation study showed that d.note revisions required fewer clarifications, and that additional techniques for expressing revision intent could be beneficial.

We introduce Family Story Play, a system that supports grandparents to read books together with their grandchildren over the Internet. Family Story Play is designed to improve communication across generations and over a distance, and to support parents and grandparents in fostering the literacy development of young children. The interface encourages active child participation in the book reading experience by combining a paper book, a sensor-enhanced frame, video conferencing technology, and video content of a Sesame Street Muppet (Elmo). Results with users indicate that Family Story Play improves child engagement in long-distance communication and increases the quality of interaction between young children and distant grandparents. Additionally, Family Story Play encourages dialogic reading styles that are linked with literacy development. Ultimately, reading with Family Story Play becomes a creative shared activity that suggests a new kind of collaborative story telling.

In this paper we introduce the TessalTable, a collaborative play system for learning about tessellations and symmetry through augmented pattern blocks. Children use tiles to "pick up" a piece of an image or video. The tiles act as containers for visual content which can be arranged and rearranged anywhere on the application surface. The tile-based controls allow for simultaneous multi-user input. A preliminary study found that children understand and engage with the interface. The ability to arrange and rearrange dynamic images invites users to explore geometric patterns and connected motion.

The Flote is a wind instrument designed for people with limited mobility. Past work in this area has failed to deliver the musical expressiveness expected of an instrument while maintaining the low cost required for wide adoption. Using only head movement and breath control, both calibrated to match the player's abilities, the Flote is an avenue for creative expression and an enjoyable form of physical therapy. The software is available as a free download at http://www.theflote.com, and the hardware can be easily built by anyone with minimal familiarity with circuits.