Enrichment is critical for zoo animal welfare. Commonly used food-based approaches have limitations in terms of sensory diversity, agency, redundancy, time budget, and nutrition. Building on research into agency-based technologies, choice-driven enrichment, and species relevant sensory engagement, we developed an interactive proximity activated scented bubble system for two American black bears (Ursus americanus). This project integrates behavioral intervention with HCI methodology to create animal-controlled olfactory enrichment. Over a three-week deployment, we assessed (1) enrichment potential through system use, behavioral diversity, and habitat use; (2) usership via engagement patterns with the bubbles; (3) sense-making and agency through anticipation behaviors; and (4) human stakeholder perspectives via visitor and staff surveys. Results show the intervention increased target foraging and locomotive behaviors compared to post-feeding baselines, generated rich multi-modal interactions, and received positive stakeholder feedback, illustrating how technology can promote animal agency while supporting zoo welfare and educational missions.

This paper evaluates interaction techniques to increase input accuracy with embodied devices—an emergent type of interactive system where the user’s body serves as both the input and output medium (e.g., gestural input via cameras/IMUs; gestural output via motors/muscle stimulation). A shortcoming of existing embodied devices is their failure to enforce alignment between users’ proprioceptive inputs and interface state. Thus, we present and evaluate interaction techniques that use muscle stimulation to enable embodied devices to: (1) recall previous interface states; (2) provide confirmation cues on state transitions; and (3) constrain inputs to valid ranges. In our study, participants performed pairs of interactions with an embodied slider, separated by a distraction task. The results showed that, compared to the same embodied slider without EMS, the combination of our techniques increased users’: (1) absolute input accuracy; (2) relative input accuracy; and (3) confidence.

Electrical muscle stimulation (EMS) has been leveraged to assist in learning motor skills by actuating the user's muscles. However, existing systems provide static demonstration—actuating the correct movements, regardless of the user's learning progress. Instead, we contrast two versions of a piano-tutoring system: a conventional EMS setup that moves the participant's fingers to play the sequence of movements correctly, and a novel adaptive-EMS system that changes its guidance strategy based on the participant's performance. The adaptive-EMS dynamically adjusts its guidance: (1) demonstrate by playing the entire sequence when errors are frequent; (2) correct by lifting incorrect fingers and actuating the correct one when errors are moderate; and (3) warn by lifting incorrect fingers when errors are low. We found that adaptive-EMS improved learning outcomes (recall) and was preferred by participants. We believe this approach could inspire new types of physical tutoring systems that promote adaptive over static guidance.

We propose, engineer, and study a novel method to augment the feeling of breathing—enabling interactive applications to let users feel like they are inhaling more/less air (perceived nasal airflow). We achieve this effect by cooling or heating the nose in sync with the user’s inhalation. Our illusion builds on the physiology of breathing: we perceive our breath predominantly through the cooling of our nasal cavities during inhalation. This is why breathing in a “fresh” cold environment feels easier than in a “stuffy” hot environment, even when the inhaled volume is the same. Our psychophysical study confirmed that our in-nose temperature stimulation significantly influenced breathing perception in both directions: making it feel harder & easier to breathe. Further, we found that <?TeX $\sim 90 \,\%$?> Math 1 of the trials were described as a change in perceived airflow/breathing, while only <?TeX $\sim 8 \,\%$?> Math 2 as temperature. Following, we engineered a compact device worn across the septum that uses Peltier elements. We illustrate the potential of this augmented breathing in interactive contexts, such as for virtual reality (e.g., rendering ease of breathing crisp air or difficulty breathing with a deteriorated gas mask) and everyday interactions (e.g., in combination with a relaxation application or to alleviate the perceived breathing resistance when wearing a mask).

Most thermal interfaces attach Peltier elements and their required cooling systems (heatsinks and fans) directly to the palm or sole, preventing users from grasping or walking. To solve this problem, we present ThermalGrasp, an engineering approach for wearable thermal interfaces that enables users to grab and walk on real objects with minimal obstruction. Our approach moves the therma l device and cooling unit to areas not used in grasping or walking (e.g., dorsal hand/foot). We then use thin, compliant materials to conduct heat to/from the palm or sole. Unlike traditional Peltiers with heatsinks, our thin materials enable grasping and walking on real objects while enjoying thermal feedback. Using our approach, a user can, for example, grasp a passive prop (e.g., a stick that acts as a torch in VR), yet feel its thermal state (e.g., hot due to its flame). In our user studies, ThermalGrasp struck a useful balance between thermal and haptic realism. We believe that ThermalGrasp is a first step towards not forcing users to choose between either feeling thermal feedback or being able to engage with grasping/walking in interactive experiences.

Low-fidelity prototyping is so foundational to Human-Computer Interaction, appearing in most early design phases. So, how do experts prototype olfactory experiences? We interviewed eight experts and found that they do not because no process supports this. Thus, we engineered Smell & Paste, a low-fidelity prototyping toolkit. Designers assemble olfactory proofs-of-concept by pasting scratch-and-sniff stickers onto a paper tape. Then, they test the interaction by advancing the tape in our 3D-printed (or cardboard) cassette, which releases the smells via scratching. Our toolkit uses commodity materials; keeps iterations quick, approachable, and cheap; and circumvents electronics, programming, and chemical handling. We evaluated Smell & Paste in two studies. We found that the toolkit was approachable to people of any technical background and that novices and experts appropriated and extended the toolkit, making it personalized. Novices produced prototypes quickly, and experts were excited about the kit's technical affordances and integrating it into their practice.

Prior research has explored modifying taste through electrical stimulation. While promising, such interfaces often only elicit taste changes while in contact with the user's tongue (e.g., cutlery with electrodes), making them incompatible with eating and swallowing real foods. Moreover, most interfaces cannot selectively alter basic tastes, but only the entire flavor profile (e.g., cannot selectively alter bitterness). To tackle this, we propose taste retargeting, a method of altering taste perception by delivering chemical modulators to the mouth before eating. These modulators temporarily change the response of taste receptors to foods, selectively suppressing or altering basic tastes. Our first study identified six accessible taste modulators that suppress salty, umami, sweet, or bitter and transform sour into sweet. Using these findings, we demonstrated an interactive application of this technique with the example of virtual reality, which we validated in our second study. We found that taste retargeting reduced the flavor mismatch between a food prop and other virtual foods.

We propose a novel type of olfactory device that creates a stereo-smell experience, i.e., directional information about the location of an odor, by rendering the readings of external odor sensors as trigeminal sensations using electrical stimulation of the user's nasal septum. The key is that the sensations from the trigeminal nerve, which arise from nerve-endings in the nose, are perceptually fused with those of the olfactory bulb (the brain region that senses smells). As such, we propose that electrically stimulating the trigeminal nerve is an ideal candidate for stereo-smell augmentation/substitution that, unlike other approaches, does not require implanted electrodes in the olfactory bulb. To realize this, we engineered a self-contained device that users wear across their nasal septum. Our device outputs by stimulating the user's trigeminal nerve using electrical impulses with variable pulse-widths; and it inputs by sensing the user's inhalations using a photoreflector. It measures 10x23 mm and communicates with external gas sensors using Bluetooth. In our user study, we found the key electrical waveform parameters that enable users to feel an odor's intensity (absolute electric charge) and direction (phase order and net charge). In our second study, we demonstrated that participants were able to localize a virtual smell source in the room by using our prototype without any previous training. Using these insights, our device enables expressive trigeminal sensations and could function as an assistive device for people with anosmia, who are unable to smell.

Current head-mounted displays enable users to explore virtual worlds by simply walking through them (i.e., real-walking VR). This led researchers to create haptic displays that can also simulate different types of elevation shapes. However, existing shape-changing floors are limited by their tabletop scale or the coarse resolution of the terrains they can display due to the limited number of actuators and low vertical resolution. To tackle this challenge, we introduce Elevate, a dynamic and walkable pin-array floor on which users can experience not only large variations in shapes but also the details of the underlying terrain. Our system achieves this by packing 1200 pins arranged on a 1.80 × 0.60m platform, in which each pin can be actuated to one of ten height levels (resolution: 15mm/level). To demonstrate its applicability, we present our haptic floor combined with four walkable applications and a user study that reported increased realism and enjoyment.

We propose a technique that allows an unprecedented level of dexterity in electrical muscle stimulation (EMS), i.e., it allows interactive EMS-based devices to flex the user's fingers independently of each other. EMS is a promising technique for force feedback because of its small form factor when compared to mechanical actuators. However, the current EMS approach to flexing the user's fingers (i.e., attaching electrodes to the base of the forearm, where finger muscles anchor) is limited by its inability to flex a target finger's metacarpophalangeal (MCP) joint independently of the other fingers. In other words, current EMS devices cannot flex one finger alone, they always induce unwanted actuation to adjacent fingers. To tackle the lack of dexterity, we propose and validate a new electrode layout that places the electrodes on the back of the hand, where they stimulate the interossei/lumbricals muscles in the palm, which have never received attention with regards to EMS. In our user study, we found that our technique offers four key benefits when compared to existing EMS electrode layouts: our technique (1) flexes all four fingers around the MCP joint more independently; (2) has less unwanted flexion of other joints (such as the proximal interphalangeal joint); (3) is more robust to wrist rotations; and (4) reduces calibration time. Therefore, our EMS technique enables applications for interactive EMS systems that require a level of flexion dexterity not available until now. We demonstrate the improved dexterity with four example applications: three musical instrumental tutorials (piano, drum, and guitar) and a VR application that renders force feedback in individual fingers while manipulating a yo-yo.

We propose a new class of haptic devices that provide haptic sensations by delivering liquid-stimulants to the user's skin; we call this chemical haptics. Upon absorbing these stimulants, which contain safe and small doses of key active ingredients, receptors in the user's skin are chemically triggered, rendering distinct haptic sensations. We identified five chemicals that can render lasting haptic sensations: tingling (sanshool), numbing (lidocaine), stinging (cinnamaldehyde), warming (capsaicin), and cooling (menthol). To enable the application of our novel approach in a variety of settings (such as VR), we engineered a self-contained wearable that can be worn anywhere on the user's skin (e.g., face, arms, legs). Implemented as a soft silicone patch, our device uses micropumps to push the liquid stimulants through channels that are open to the user's skin, enabling topical stimulants to be absorbed by the skin as they pass through. Our approach presents two unique benefits. First, it enables sensations, such as numbing, not possible with existing haptic devices. Second, our approach offers a new pathway, via the skin's chemical receptors, for achieving multiple haptic sensations using a single actuator, which would otherwise require combining multiple actuators (e.g., Peltier, vibration motors, electro-tactile stimulation). We evaluated our approach by means of two studies. In our first study, we characterized the temporal profiles of sensations elicited by each chemical. Using these insights, we designed five interactive VR experiences utilizing chemical haptics, and in our second user study, participants rated these VR experiences with chemical haptics as more immersive than without. Finally, as the first work exploring the use of chemical haptics on the skin, we offer recommendations to designers for how they may employ our approach for their interactive experiences.

We explore a temperature illusion that uses low-powered electronics and enables the miniaturization of simple warm and cool sensations. Our illusion relies on the properties of certain scents, such as the coolness of mint or hotness of peppers. These odors trigger not only the olfactory bulb, but also the nose's trigeminal nerve, which has receptors that respond to both temperature and chemicals. To exploit this, we engineered a wearable device based on micropumps and an atomizer that emits up to three custom-made "thermal" scents directly to the user's nose. Breathing in these scents causes the user to feel warmer or cooler. We demonstrate how our device renders warmth and cooling sensations in virtual experiences. In our first study, we evaluated six candidate "thermal" scents. We found two hot-cold pairs, with one pair being less identifiable by odor. In our second study, pParticipants rated VR experiences with our device trigeminal stimulants as significantly warmer or cooler than the baseline conditions. Lastly, we believe this offers an alternative to existing thermal feedback devices, which unfortunately rely on power-hungry heat-lamps or Peltier-elements.