Providing tactile-feedback when users contact virtual-interfaces has been a seminal advance. However, we posit these advances have been explored in isolation from considerations of users’ physical interactions with surrounding-objects. Most touch-interfaces were designed to optimize virtual interfaces, but rarely consider that users also need to feel physical interfaces (e.g., tools, putting on/off headsets). We argue against this being the sole design-objective driving haptic-interfaces; instead, we propose also to optimize the fidelity of the real-world sensations that users feel while wearing a haptic device. We propose a framework to classify touch-devices by measuring not only their abilities to deliver virtual-feedback but also how much they impair physical-feedback—we argue this balancing act is an urgent mainstream need, given the success of Mixed-Reality. Thus, to accelerate the research in this area, we synthesize existing techniques into new conceptual-categories: feel-through, on-demand, relocated, and remote actuators. Finally, we present their pros/cons and discuss a possible roadmap.

We introduce Power-on-Touch, a novel method for powering devices during interaction. Power-on-Touch comprises two main components: (1) a wearable-transmitter attached to the user's body (e.g., fingernail, back of the hand, feet) with wireless power-coils and a battery; and (2) receiver-tags embedded in interactive devices, making them battery-free. Many devices only require power during interaction (e.g., TV remotes, digital calipers). We leverage this interactive opportunity by inductively transferring energy from the user's coil to the device's coil when in close proximity. To achieve this, we engineered receiver-tags and coils, including thin pancake-coils best-suited for wearables and spherical-coils that receive power omnidirectionally. To understand which coils best support a wide range of interactions (e.g., grasping, touching, hovering), we performed technical characterizations, including impedance and 3D efficiency analysis. We believe our technical approach can inspire ubiquitous computing with new ways to scale up the number and diversity of battery-free devices, not just sensors (µWatts) but also actuators (Watts).

We present Stick&Slip, a novel approach that alters friction between the fingerpad & surfaces by depositing liquid droplets that coat the fingerpad. The liquid coating modifies the finger's coefficient of friction, allowing users to feel surfaces up to ±60% more slippery or sticky. We selected our fluids to rapidly evaporate so that the surface returns to its original friction. Unlike traditional friction-feedback, such as electroadhesion or vibration, our approach: (1) alters friction on a wide range of surfaces and geometries, making it possible to modulate nearly any non-absorbent surface; (2) scales to many objects without requiring instrumenting the target surfaces (e.g., with conductive electrode coatings or vibromotors); and (3) both in/decreases friction via a single device. We identified nine liquids and characterized their practicality by measuring evaporation rates, etc. To illustrate the applicability of our approach, we demonstrate how it enables friction in virtual/mixed-reality or, even, while using everyday objects/tools.

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.

Users often 3D model enclosures that interact with significant heat sources, such as electronics or appliances that generate heat (e.g., CPU, motor, lamps, etc.). While parts made by users might function well aesthetically or structurally, they are rarely thermally-sound. This happens because heat transfer is non-intuitive; thus, engineering thermal solutions is not straightforward. To tackle this, we developed ThermalRouter, a CAD plugin that assists with improving the thermal performance of their models. ThermalRouter automatically converts regions of the model to be made from thermally-conductive materials (such as nylon or metallic-silicone). These regions act as heat channels, branching away from hotspots to dissipate heat. The key is that ThermalRouter automatically simulates the thermal performance of many possible heat channel configurations and presents the user with the most thermally-sound design (e.g., lowest temperature). Furthermore, it allows users to customize by balancing costs, indicating non-modifiable geometry, etc. Most importantly, ThermalRouter achieves this without requiring manual labor to set up or parse the results of complex thermal simulations.

Robot-initiated touch is a promising mode of expression that would allow robot caregivers to perform physical tasks (instrumental touch) and provide comfort (affective touch) in healthcare settings. To understand the factors that shape how people respond to touch from a robotic caregiver, we conducted a crowdsourced study (N=163) examining how robot-initiated touch (present or absent), the robot’s intent (instrumental or affective), robot appearance (Nao or Stretch), and robot tone (empathetic or serious) impact the perceived quality of care. Results show that participants prefer instrumental to affective touch, view the robot as having greater social attributes (higher warmth, higher competence, and lower discomfort) after robot-initiated touch, are more comfortable interacting with the human-like Nao than the more machine-like Stretch, and favor consistent robot tone and appearance. From these results, we derived three design guidelines for caregiving robots in healthcare settings.

We propose a new type of haptic actuator, which we call MagnetIO, that is comprised of two parts: one battery-powered voice-coil worn on the user's fingernail and any number of interactive soft patches that can be attached onto any surface (everyday objects, user's body, appliances, etc.). When the user's finger wearing our voice-coil contacts any of the interactive patches it detects its magnetic signature via magnetometer and vibrates the patch, adding haptic feedback to otherwise input-only interactions. To allow these passive patches to vibrate, we make them from silicone with regions doped with polarized neodymium powder, resulting in soft and stretchable magnets. This stretchable form-factor allows them to be wrapped to the user's body or everyday objects of various shapes. We demonstrate how these add haptic output to many situations, such as adding haptic buttons to the walls of one's home. In our technical evaluation, we demonstrate that our interactive patches can be excited across a wide range of frequencies (0-500 Hz) and can be tuned to resonate at specific frequencies based on the patch's geometry. Furthermore, we demonstrate that MagnetIO's vibration intensity is as powerful as a typical linear resonant actuator (LRA); yet, unlike these rigid actuators, our passive patches operate as springs with multiple modes of vibration, which enables a wider band around its resonant frequency than an equivalent LRA.