Haptics: Understanding Touch; Technology and Systems; Applications and Interaction

This study seeks a method to improve the perceived intensity of a mid-air ultrasonic tactile stimulus based on the perceptual phenomenon of tactile enhancement. We present a brief vibrotactile stimulus to the wrist before stimulating the user’s palm using a mid-air ultrasonic stimulus. The two stimuli have the same frequency. This arrangement is similar to the typical situation in which tactile enhancement occurs, except that the stimulation locations are close but different and the following stimulus is of mid-air ultrasonic type. Our method is validated by a user study demonstrating the perceived intensity of a mid-air ultrasonic stimulus is increased up to 1.7 times. These findings offer a new research direction to amend the most critical problem of current mid-air ultrasonic haptic devices, the weak perceptual strength, using a common wearable.

In our daily activities, we utilize not only the finger pad but also the sides and hemispherical ends of the fingers when handling an object. Therefore, providing tactile perception across the entire fingertip is deemed crucial for achieving advanced teleoperation. To fulfill this goal, understanding the spatial acuity distribution of the fingertip becomes imperative. Although it is generally known that the tactile acuity of the fingertip is different from that at the end of the finger and the finger pad, the details of such a change in resolution are not known, nor is the resolution of the side of the finger. We measured the spatial acuity of the entire fingertip in detail and found that the tactile acuity from the finger end to the finger pad changes almost linearly, with a steep decrease in tactile acuity at the finger side.

Electrotactile stimulation involves the direct stimulation of tactile receptors with a small electrical current and has advantages such as device miniaturization and high responsiveness. However, there are large individual differences in the sensations generated, which requires each user to adjust the current intensity before experiencing tactile sensation. This is a common disadvantage of electrotactile stimulation and hinders its practical use. In this study, we propose a method for measuring skin impedance (i.e., resistance (R) and capacitance (C)) in real time and estimating the individual stimulated current using machine learning. We measured skin impedances by fitting the voltage waveform between the anodic and cathodic electrodes to an exponential curve when stimulating a constant current pulse. We used 0.2 and 0.4 mA of prepulses (before stimulation) to estimate the electrical current of sensation threshold during cathodic stimulation. Results confirmed that machine learning can be used to estimate the stimulated current, and random forest regression was the most appropriate method (mean correlation coefficient of r2 = 0.95). The machine learning model was tested on 10 participants, which showed that the sensation threshold varied from 0.8 to 1.4 of the estimated value.

In this study, we aimed to elucidate the mental representation of material categories based on temperature perception. To achieve this, we employed a thermal display to simulate materials based on a thermal model where thermal effusivity is the key thermal property. Participants were prompted to evaluate the perceived materialness of these simulated materials across eight material categories. This approach not only allowed us to observe the relationship between thermal effusivity and the mental representation of material categories, but also to propose a mental representation model represented by a Gaussian function.

Current haptic surfaces performing friction modulation still do not convey realistic shape sensations. In this study, we designed three elongated shapes that were rendered by ultrasonic lubrication within their inner area: a straight line, a sine and a second-degree polynomial. For these three shapes, we investigated how design properties such as the shape’s complexity and thickness can influence users recognition of the displayed 2D shape and their strategy for haptic exploration on the display. A first experiment focused on recognition of shapes with varying complexity and on whether the increased or decreased friction within the shape impacts its perception. A second experiment focused on studying the influence of the shape thickness on the recognition rate of two shapes: the straight line and the sine. In experiment 1, participants recognized the line and sine quite well while performance with the polynomial was at chance level. In addition, whether friction was increased or decreased compared to the surrounding area did not impact shape recognition. In experiment 2, participants’ recognition performance decreased for larger thickness. Analysis of the finger trajectory in experiment 1 showed that participants who followed closely the shapes performed better than participants who broadly scanned the surface. Taken together, our results suggest that friction recognition alone does not enable accurate recognition of straight or curved 2D shapes. However, parameters related to the friction contrast or the width of the stimulation area can enhance the user capacity to perceive shapes on the screen by touch.

When interacting with surfaces, humans perceive surface attributes which are often accompanied by affective responses. Notably, rough materials tend to evoke unpleasant feelings whereas some soft materials are frequently associated with pleasantness. While the literature predominantly focused on the relationship between solid objects and pleasantness, our daily haptic interactions also include fluids. Here, our main objective was to explore the relationship between unpleasantness and perceived qualities of touched fluids. We created a stimulus set by varying fluid properties of real-life materials (e.g., diluting honey with water). Participants actively explored the materials without time or movement constraints. In a first presentation block, they rated the unpleasantness of the materials while in a second block, they evaluated the materials based on seven sensory adjectives. Principal Component Analysis on adjective ratings revealed the dimensions characterizing differences in sensory qualities of our materials: viscosity and slipperiness. Importantly, we observed a positive significant correlation between unpleasantness and viscosity while no correlation was found for slipperiness. Specifically, materials perceived as more viscous felt unpleasant, emphasizing the role of viscosity in affective responses during haptic exploration. Overall, the current study contributes to the broader understanding of unpleasantness by extending our knowledge beyond the traditionally studied solid materials.

We hypothesize that cross-modal integration can shift the haptic perception of vibrotactile frequency in the presence of concurrent audio stimuli. The feasibility and extent of this hypothesis are examined in two psychophysical experiments. The first experiment focuses on the core hypothesis, comparing purely vibrotactile feedback against vibrotactile feedback accompanied by audio stimuli of various frequencies. In the second experiment, we quantify the difference in vibrotactile perception that users perceive in the presence of concurrent audio feedback. The results show that concurrent low-frequency aural stimulation has a significant effect on the perception of high-frequency vibrations.

In this study, we investigate the capability of ultrasound to present softness and hardness sensations through physically limited stimuli, thereby extending mapping to the stiffness properties of objects in the real world. By applying spatiotemporal modulation in mid-air ultrasound tactile displays, we alter the radius of the focus trajectory based on a finger’s vertical movement. Thus, the contact process with objects of different compliance is presented by varying the contact area. In addition to the radius change, we set a series of speed levels to alter the perceived intensity during pressing. Through psychophysical experiments, we investigate the rendering realism and softness perception of the presented rendering method. Stimuli with a low focus speed and a large rate of change of contact area during pressing are perceived as softer. Moreover, we achieve a 4.5-fold softness range between the softest and hardest stimuli while maintaining a certain level of rendering realism.

The importance of exploring the presenting location and type of tactile stimuli has grown along with various applications of haptic feedback. We measured the just noticeable differences (JNDs) for the vibrotactile and squeezing stimuli applied to the wrist to reveal the perceptual characteristics of each stimulus. We set the upper limit as the intensity perceived as unpleasant by individuals, and we used the same percentage of each individual’s upper limit as the reference stimulus. This methodology allows for the normalization of the intensity of reference stimuli, provides a consistent scale across individuals, and facilitates the comparison of perceptual sensitivity across different sensory stimuli. The results of the psychophysical experiments showed that for vibrotactile stimuli, the Weber ratio remained constant across different stimulus intensities, whereas that of the squeezing stimulus was higher at lower intensities and lower at higher intensities. These results indicate that each stimulus type has high-resolution regions, emphasizing the importance of selecting an appropriate stimulus based on specific environments and information.

While visual and auditory information are prevalent in modern multimedia systems, haptic interaction, e.g., tactile and kinesthetic interaction, provides a unique form of human perception. However, multimedia technology for contact interaction is less mature than non-contact multimedia technologies and requires further development. Specialized haptic media technologies, requiring low latency and bitrates, are essential to enable haptic interaction, necessitating haptic information compression. Existing vibrotactile signal compression methods, based on the perceptual model, do not consider the characteristics of fused tactile perception at multiple spatially distributed interaction points. In fact, differences in tactile perceptual importance are not limited to conventional frequency and time domains, but also encompass differences in the spatial locations on the skin unique to tactile perception. For the most frequently used tactile information, vibrotactile texture perception, we have developed a model to predict its perceptual importance at multiple points, based on self-supervised learning and Spatio-Temporal Graph Neural Network. Current experimental results indicate that this model can effectively predict the perceptual importance of various points in multi-point tactile perception scenarios.

Many studies have investigated methods for presenting the sensation of touching hair, and tactile devices dedicated to this sensation have been proposed. However, the tactile factors that cause the sensation of hair have not been clarified, which is why the synthetic presentation of the sensation using tactile devices for general purposes is difficult. In this study, we considered four factors contributing to the tactile sensation of hair: thickness, density, contact area, and stiffness. This study aims to investigate the impact of these factors on the tactile sensation of hair and hair-likeness. We used 3D-printed tactile patterns to change the thickness, density, and contact area; the thickness and density were defined by the diameter and interval of cylindrical bumps on the pattern. The contact area was defined by the elevation angle of the pattern at which the pattern curves along the finger. A spring-based elastic support mechanism was used to change the stiffness. In the experiment, participants were asked to imagine human hair and evaluate their subjective level of hair-likeness when touching the pattern. The results showed that the ratings of hair-likeness were highest when the density was approximately 0.7 mm in interval and the contact area was approximately $${60}^\circ $$ 60 ∘ elevation angle. Regarding thickness and stiffness, an optimal value was not found among the conditions in the experiment; hair-likeness was higher when the thickness was lesser and the stiffness was lower.

Signals from different senses are integrated into multisensory events or segregated according to their temporal and spatial relations. If signals are integrated, we perceive synchrony between them even in the presence of slight stimulus onset asynchronies (SOA). The range of SOAs during which physically asynchronous signals are perceived to be synchronous is called the temporal binding window (TBW). The TBW depends on various factors. Here we investigated how spatial congruency affects the width of the visuotactile TBW in a naturalistic setting, given that spatial congruency of signals in the single senses should promote multisensory integration and thereby binding. In a virtual reality (VR) environment, we presented visual and vibrotactile stimuli in different locations. Vibrotactile stimuli were presented on the participants’ hands or forearms, and visual stimuli were rendered in real time on virtual counterparts of the tracked hands or forearms. We varied SOAs between vision and touch and asked if visual and tactile stimuli had occurred synchronously. Similar to what has been found in the audiovisual domain, the temporal binding window was wider when visual and tactile stimuli were spatially congruent—possibly due to enhanced multisensory integration. Thus, we extend the previous findings and conclusions on spatial congruency effects to visuotactile interactions in VR environments.

This paper investigates the influence of contact force applied to the human’s fingertip on the perception of hot and cold temperatures, studying how variations in contact force may affect the sensitivity of cutaneous thermoreceptors or their interpretation. A psychophysical experiment involved 18 participants exposed to cold ( $${20}\,^{\circ }\text {C}$$ 20 ∘ C ) and hot ( $${38}\,^{\circ }\text {C}$$ 38 ∘ C ) thermal stimuli at varying contact forces, ranging from gentle (0.5 N) to firm (3.5 N) touch. Results show a tendency to overestimate hot temperatures (hot feels hotter than it really is) and underestimate cold temperatures (cold feels colder than it really is) as the contact force increases.This result might be linked to the increase in the fingertip contact area that occurs as the contact force between the fingertip and the plate delivering the stimuli grows.

This paper investigates differences in normal force for different tracing directions on the basis of friction, taking into account individual differences. The normal force and friction coefficient were measured when sixteen participants naturally traced samples with different friction coefficients in the backward and lateral directions. The results showed that participants applied significantly larger force in the backward direction than in the lateral direction. The coefficient of friction was also significantly higher in the backward direction. In addition, both the normal force and the coefficient of friction varied among individuals. Those with higher coefficients of friction used relatively small normal force, whereas those with lower coefficients of friction tended to have large variance in the normal force.

A generally adaptive way to regulate emotions involves using reappraisal to change the motivational meaning of a distressing situation. Learning and using this strategy can be challenging, especially in intense situations and for vulnerable individuals. Technologies intended to facilitate learning and using reappraisal have mostly relied on verbal communication. Here, we consider the potential for complementing existing approaches with haptic technologies, on the premise that crafted touch interaction can increase intervention accessibility and adaptiveness, both during intense situations and over longer time scales. We discuss the psychological and physiological pathways through which a haptic intervention could make reappraisal easier to learn and use; then propose requirements for CHORA (comforting haptic co-regulating adjunct) technology and a research approach to its validation.

It is known that skin deformations on the side of finger contribute to force perception in the fingertip. This study focuses on this knowledge and proposes a method to present force sensation by transcutaneous electrical stimulation via the side of the finger. The compactness of the proposed method makes it suitable for mounting on the fingertip. Moreover, it does not interfere with the tactile sensation of the fingertip, making it easy to combine with other methods such as vibration presentation. Our system is composed of electrodes on the lateral side of fingertip and dorsal surface of middle finger joint. Using this system, we examined the effect of electrical stimulation to the perception of weight during grasping. The results revealed a tendency to perceive the weight of the grasped object to be larger with the stimulation.

Haptic feedback is a key component in human-computer interaction, providing human users with immersive and realistic experiences. Thermal feedback, a form of haptic feedback, enables users to recognize the materials of virtual objects by simulating changes in skin temperature during hand-object interactions. In order to carry out these simulations, it is essential to characterize skin temperature changes as the basis for the simulations. One of the characterizing methods is utilizing the data on the change in skin temperature directly measured. Creating a dataset of the changes in skin temperature during hand-object interactions with human fingers presents challenges due to inconsistent measurement settings and laborious processes. An artificial finger with thermal properties similar to those of human fingers could overcome the problems. In the present study, we analyzed the tolerance range of the thermal effusivity for the artificial finger, aiming to replicate thermal transients akin to those in human fingers during hand-object interactions. This range was investigated using a thermal model that predicts skin temperature change based on the thermal properties of skin and materials. As a result, the thermal effusivity of the artificial finger is required to be in the range of 1090 to 1281 $$(J/m^2$$ ( J / m 2 s $$^{1/2}K)$$ 1 / 2 K ) for the measurement to be valid when the contact material spans a wide thermal property range. Based on these findings, we discuss candidate materials for the artificial finger and the potential applications in a machine-learning model for thermal displays, as well as an automatic material classification system based on thermal cues for robot hands.

Wearable haptic devices have been proposed to convey guidance and feedback information in a variety of applications, ranging from navigation to virtual interaction and prosthetics. A design approach for armband devices using an actuated fabric belt and gearmotors actuators has been proposed and widely experimented in the field. In this work we experiment whether the use of direct-drive actuation in place of servomotors proves effective in rendering lower intensity, but cleaner linear feedback. Interestingly, the method allows for modulation of vibrotactile feedback as well, with the same actuation design. Here we present the design of a wearable haptic device for the upper limb, implementing a 2 degrees of freedom direct drive transmission and a soft belt interface. Experiments evaluate the capability of the haptic feedback to guide participants in two different motor tasks, exploiting the two haptic modalities the device can render: clenching and lateral stretch. Moreover, the addition of modulated vibrotactile feedback to the conventional linear motor activation is explored as a viable modality to enhance the perception and effectiveness of the perceived stimuli.

Understanding the interplay between surface roughness and material elasticity in haptic texture perception is important. In the real world, these characteristics do not occur isolated from one another, yet, the haptic perceptions of surface features and material properties are often investigated individually. This highlights the need for suitable stimulus material for haptic perceptual experiments. The present research details the manufacturing and validation of a database of stochastically-rough, elastic stimuli tailored for haptic perceptual experiments. The stimulus set comprises 49 3D-printed samples, offering a systematic variation in stochastic microscale roughness and material elasticity, replicating natural surface features without compromising experimental control. The surfaces were generated using an algorithm that produces randomly rough surfaces with well-defined spectral distributions, demonstrating fractal properties over a large range of length scales. Controlled variations in elasticity were implemented via variations of the printing material composition. Finally, we present preliminary perceptual data from two observers, illustrating the discriminability of the stimulus space for roughness and softness discrimination. This database aims to facilitate haptic research on material and texture perception, offering a controlled yet naturalistic set of stimuli to explore the intricate interplay between surface roughness and material elasticity in shaping haptic texture perception.

This study aims to develop a compact, palm-free wearable system for mixed-reality (MR) environments that does not interfere with interactions with real objects. We propose a novel wearable system that presents the direction of force through a rotational skin-stretch distribution to the wrist by utilizing four independently controlled rotating tactors. Two control rules, local and global, are proposed to dictate the stimulus distribution. The local stimulus distribution produces a local distortion distribution by combining the rotation of two specific tactors and suggests a direction. The global control rule aims to present the overall direction of the force by combining the directional forces presented on both the palm and back of the hand. The capability of the system to present the perceptual intensity and directional stimuli was confirmed through two experiments. The first experiment confirmed that the proposed system could present perceived intensity. The second experiment showed that the global control law could present stimuli in the front-back direction, whereas the local control law could present stimuli in other directions except for upwards. These findings suggest that proposed system has potential to enhance MR experience by simulating static force sensations, such as the weight of virtual objects.

We present a new handheld multi-actuator haptic device, which provides localized vibrotactile feedback in a small form-factor. To isolate the vibrations generated from the different actuators, we design an original 3D printed deformable structure integrated into the handle. We evaluate the benefits of our isolation structure in a vibrometry study, comparing the proposed version to a rigid structure. A perception study is also conducted to evaluate the distinct perception of vibrations between the two versions of the handle by 12 human users. Finally, we showcase the use of the proposed handle in a virtual navigation task, showing its capabilities for applications where multiple and distinct haptic stimuli need to be provided to the user’s hand.

Haptic feedback is becoming a crucial element for enhancing immersion in various media applications. To enrich this feedback, high-quality haptic content, an appropriate playback device, and efficient codecs for transmission are essential. This paper introduces a novel vibrotactile codec that employs an autoencoder architecture integrated with Convolutional Neural Networks (CNNs). It leverages a tailored perceptual model with a band structure derived from the audio domain, optimizing the perceived quality of the encoded signals during training. Additionally, we have developed and assessed multiple perceptual training losses to further enhance the performance of our codec.

The “hanger reflex” is an illusion in which a strong rotational force is induced on the head by wearing a wire hanger around the head. This phenomenon, which is caused by shear deformation of the skin due to compression, has been confirmed in several parts of the body other than the head. Because this phenomenon can present a sense of force using lightweight devices, a potential application of this phenomenon is supporting upper-limb rehabilitation. While the wrist and elbow are applicable locations of this phenomenon on the upper limbs, these locations alone are not sufficient to cover all rehabilitation movements. To increase the applicable rehabilitation movements, new applicable locations are needed. Therefore, we propose shoulder as a new application body part. Using methods employed in other locations, a device was developed to present the shear deformation of the skin to the shoulder. We conducted an experiment to verify the perception of force along the shoulder with the developed device. The result suggested that participants were able to perceive the force from the presented forward and backward shear deformation of the skin.

Kinesthetic wearables that allow freedom of movement and diversified gestures with various haptic feedback in virtual reality and that are affordable for the public are still lacking. Indeed, existing wearables tend to rely on expensive actuators or lack diversified and tunable haptic feedback, or may be complex to implement. Thus, we propose a wearable for the hand using a new haptic brake based on active lubrication. It enables force modulation up to 3.15 N and tunable vibrotactile feedback from 1 Hz to 100 Hz through a unique passive actuator, while being light, low cost and safe. To assess the possibility of providing diversified and tunable feedback, we conducted a user study with 12 participants. The results showed that different vibrotactile patterns could be potentially recognized and that three absolute levels of force could be easily identified.

In our previous research, we introduced a technique for creating a natural tracing sensation. This was achieved by touching a rotating a small disk, the size of a fingertip. This approach is advantageous due to its compact design and the use of the physical sliding of objects. However, its limitation lies in its inability to represent multiple textures, limited to the surface material of the rotating disk. In contrast, numerous studies have explored varying textures through vibration. Consequently, we explored the potential of simulating diverse textures by merging this vibrational texture representation with the tracing sensation produced by the rotation of the disk. Based on this concept, we developed a system that provides stimulation through both disk rotation and vibration. Our system utilizes the same actuator for both rotating and vibrating the disk. We carried out an experiment to assess how realistic the generated stimulus feels, comparing it to the sensation of tracing an actual 1D grating plate. The findings indicated that we can realistically replicate multiple textures with varying degrees of roughness. Furthermore, our results showed that in many instances, the difference between the bump spacing and the vibration frequency had minimal impact on the perceived realism.

In this study, we explored the emotional impact of a visuo-tactile cutaneous rabbit effect (CRE) within a virtual reality (VR) context. Participants experienced tactile sensations on their forearms while interacting with 3D models of various visual stimuli (rabbit, kangaroo, spider, grasshopper, frog, flea, and sphere) in a VR environment hopping along a virtual arm, visually and positionally synchronized with the participant’s real arm. The CRE was induced by delivering three successive bursts of tactile stimulation at different forearm locations. We manipulated the virtual experience by having the 3D models either hop thrice, mirroring the tactile stimuli, or nine times, creating a more distributed sensory illusion across the arm. Results show that the type of visual stimulus significantly influenced emotional responses. Spiders were consistently rated as more unpleasant than rabbits, kangaroos, and spheres. The frequency of hops also played a crucial role; fewer hops led to higher valence ratings for visually pleasant stimuli, consistent with previous findings. An increase in visual hops generally had a calming effect, particularly notable for stimuli like fleas. In terms of dominance, participants felt less in control with spider stimuli compared to spheres. Tactile feedback was pivotal in enhancing realism and emotional depth, with varying feedback patterns suggesting potential for more nuanced and realistic VR experiences. The findings suggest that tactile stimulation in VR can significantly alter emotional responses to different stimuli, highlighting the importance of effectively coordinated multisensory feedback in virtual environments.

In the human body, skin stretch is intrinsically related to motion execution, providing important proprioceptive cues for movement perception and control, as is the case of human hands and fingers. However, as of today, a quantification of the amount of skin stretch across multiple hand joints notably lacks. In this study, we aim at bridging this research gap, quantifying skin stretch on the dorsal part of hand fingers, and more specifically across Proximal InterPhalangeal (PIP) and MetaCarpal (MCP) joints. We correlated the estimated skin stretch with human hand kinematics, in grasping tasks with several items. Twelve able-bodied participants were required to grasp twenty objects. We used an RGB-D camera for reconstructing hand kinematics (more specifically PIP and MCP values), while optical markers were placed on the hand dorsum to estimate skin displacement across joints. We characterized the relationship between joint angles and the corresponding skin stretch estimation over time using a linear regression analysis, with no statistically significant differences between participants and objects. The experimental data we collected are publicly available at this link [1]. This research sheds light on the intricate interplay between skin stretch and hand/finger movements. These outcomes can pave the path to the design of non-invasive skin stretch-based feedback devices for accurately conveying hand proprioceptive cues, with interesting implications for rehabilitation and advanced human-machine interaction.

Even though audio-visual stimuli are widely used for information communication, vibration feedback offers an attractive alternative due to its confidentiality, high ability to attract attention, and effectiveness in conveying an appropriate level of urgency. In this study, we investigate how the perceived level of urgency is modulated by a simulated driving task. To examine this, we conducted two experiments. The first experiment aimed to design vibration stimuli capable of eliciting three levels of urgency (low, medium, and high) by leveraging critical vibration parameters, such as vibration intensity, vibration duration, upper body part, and surface area. Results of the first experiment show significant differences in the perceived urgency of the three stimuli, which validates the ability of vibration to elicit the three levels of urgency (Kruskal-Wallis test, Bonferroni-Holm correction, $$p<0.05$$ p < 0.05 ). In the second experiment, we evaluate how the perceived urgency of the three vibration stimuli is modulated during a simulated driving task. Results indicate that medium urgency vibration is sufficient to elicit a high sense of urgency (there is no significant difference in the perceived urgency between the medium and high urgency vibration). On the other hand, high urgency vibration significantly increases annoyance as compared to medium urgency vibration (One-way ANOVA test, Bonferroni-Holm correction, $$p<0.05$$ p < 0.05 ). The results show that the perceived urgency of the same stimulus can vary due to the driving simulation task. From these results, we also suggest that a primary task significantly modulates the perceived urgency and must be considered while designing vibration stimulation to convey a desirable level of urgency.

Numerous studies have provided vibrotactile warning patterns for vehicles, but efforts to faithfully incorporate users’ designs were difficult to find. This work adopts a participatory design using a vibration authoring tool to fully utilize user-defined design and determine representative patterns for various warning scenarios. We consider a driving seat with three vibrotactile actuators stimulating the driver’s back and two thighs. Haptics experts also craft two sets of vibrotactile warnings, which emphasize spatial consistency to warning event directions and prioritize congruence to commercial auditory warnings, respectively. The user-defined and two expert-designed sets are compared by a user study, which reveals the general drivers’ preference for simple and clear patterns. Specific pattern configurations and design implications across diverse warning scenarios can serve as practical guidelines for in-vehicle warning designers.

Engaging in cognitive activities early and regularly has been shown to improve cognitive performance and delay the natural progression of cognitive decline for older adults. Many factors can make it difficult to achieve this, such as lack of engagement, highlighting the potential for technology to enhance engagement with cognitive activities. This paper investigates the unique combination of haptic feedback and a Socially Assistive Robot (SAR) during categorization-based activities. In this experiment, passive and active kinesthetic force feedback led to improvements in factors such as usability and affective state compared to non-contact cutaneous (ultrasonic) feedback. The robot facilitation positively impacted older adults’ performance and their perception of usability and interactivity compared to using a laptop. Some design considerations emerged including the themes of control and informativeness of haptic feedback and the proxemics of the robot. This work supports the combination of haptic feedback, specifically force feedback, along with a SAR to foster engagement with cognitive activities for older adults.

As virtual reality environments evolve, users should be able to interact with real objects while also receiving artificially designed sensory cues - such as those from haptic devices. Our research examines wearable haptic devices that provide feedback at the wrist, enabling free fingertip movement. Limited prior work has studied how the shift in feedback location (from fingertips to wrist), called referred haptics, affects perception in a multisensory context. To explore this effect under visual and haptic sensory integration, we ran a within-subjects 2I-2AFC study. Participants chose what they perceived to be the stiffer of two springs in virtual reality while receiving haptic feedback at the wrist through squeezing. We tested three different sets of spring stiffness and five levels of visual manipulation. Two different discrimination strategies were observed among participants – haptic-focused and visual-focused. Notably, the visual-focused participants showed reduced accuracy with greater stiffness differences and more pronounced visual cues. Interaction times also varied according to the study conditions and post-fact groups. Our insights underscore the importance of considering sensory priors in multisensory integration research, particularly for referred haptic feedback.

Watching Autonomous Sensory Meridian Response (ASMR) videos is a popular approach to support mental well-being, as the triggered ASMR tingling sensation supports de-stressing and regulating emotions. Therefore, there is increasing research on how to efficiently trigger ASMR tingling sensation. Tactile sensation remains unexplored because current popular ASMR approaches focus on the visual and audio channels. In this study, we explored the impact of tactile feedback on triggering ASMR tingling sensation in a Virtual Reality (VR) environment. Through two experimental studies, we investigated the relaxation effect of a tactile-enabled ASMR experience, as well as the impact of vibrotactile triggers on the ASMR experience. Our results showed that vibrotactile feedback is effective in increasing the likelihood of ASMR tingling sensation and enhancing the feeling of comfort, relaxation, and enjoyment.

A Haptic Experience may take many shapes or forms, ranging from simple UI notifications on a phone, to fully immersive multi-sensorial experiences. In this context, dedicated Haptic authoring tools have been flourishing and the literature on Haptic design introduced many concepts and guidelines to improve Haptic Experiences. In this paper, we propose to go beyond haptic design and explore the potential of end-user customization of Haptic Experiences. First, we discuss and extend a theoretical model of Haptic Experience. We revisit the proposed design parameters to account for the spatialized notion of haptic feedback and study the suitability of these parameters for end-user customization. Then, we detail a user study (n = 52) exploring how users can customize different haptic effects (18 different effects) through haptic customization parameters, i.e., intensity and spatial density. Finally, our results indicate significant variability in these parameters depending on the context and provide directions for future user studies regarding haptic profile design determined by subjective data.

This paper presents a way of creating and working with lo-fi materials for a tactile refreshable pin display. The materials were seen to work well, and supported co-design discussions around the future design of, and interaction with, the – as yet, non-existing – tactile device.

We investigate the influence of thermal haptic feedback on stress during a cognitive task in virtual reality. We hypothesized that cool feedback would help reduce stress in such task where users are actively engaged. We designed a haptic system using Peltier cells to deliver thermal feedback to the left and right trapezius muscles. A user study was conducted on 36 participants to investigate the influence of different temperatures (cool, warm, neutral) on users’ stress during mental arithmetic tasks. Results show that the impact of the thermal feedback depends on the participant’s temperature preference. Interestingly, a subset of participants (36%) felt less stressed with cool feedback than with neutral feedback but had similar performance levels, and expressed a preference for the cool condition. Emotional arousal also tended to be lower with cool feedback for these participants. This suggests that cool thermal feedback has the potential to induce relaxation in cognitive tasks. Taken together, our results pave the way for further experimentation on the influence of thermal feedback.

Hand-tracking technologies allow interactions with virtual environments unmediated by any physical tool. Mid-air haptic technologies further this interaction paradigm by providing the user with tactile feedback. As an additive sensation not strictly bound to physical-based laws of objects, there is much room for exploration of various integration methods. Here, we investigate whether the psychological variable known as the sense of agency (SoA) is sensitive to variations of a mid-air haptic stimulus, where SoA captures the user’s feeling of control and causal influence in the virtual environment. To that end, we use a virtual button press-tone (action-effect paradigm) to measure SoA at the behavioural level as well as through self-report. Mid-air haptics accompanying the visual element of the virtual button press were varied at 4 levels: dynamic, fixed, on completion and no feedback. Results show a significant influence at the behavioural level but were not self-reported. Additive mid-air haptics that was not congruent with the visual elements negatively impacted the implicit feeling of SoA.

Co-creative computer agents can be used to support designers they work alongside. However, this approach to co-creativity has not been studied in haptics. In this paper, we investigate this topic by applying an interactive reinforcement learning technique developed for sound synthesis to a two degree-of-freedom force-feedback design space. We developed a prototype authoring tool to study the interaction between designers and this type of co-creative agent. As these agents are trained on the designer’s feedback in real-time, this method is flexible and could be applied to other hardware and software configurations. Five participants were recruited to use the tool in two artistic tasks and were interviewed about their experiences. An analysis of the participants’ comments and actions indicated that co-creation in haptics can help designers explore new effects if they are sufficiently able to control the extent and direction of exploration.

The paper presents a system for simulating surfing in Virtual Reality (VR), emphasizing the recreation of aquatic motions and user-initiated propulsive forces using a 6-Degree of Freedom (DoF) motion platform. We present an algorithmic approach to accurately render surfboard kinematics and interactive paddling dynamics, validated through experimental evaluation with $$N=17$$ N = 17 participants. Results indicate that the system effectively reproduces various acceleration levels, the perception of which is independent of users’ body posture. We additionally found that the presence of ocean ripples amplifies the perception of acceleration. This system aims to enhance the realism and interactivity of VR surfing, laying a foundation for future advancements in surf therapy and interactive aquatic VR experiences.

Wearable haptic devices are portable and unobtrusive technologies able to provide tactile sensations to the human skin. Their use in Augmented Reality (AR), where visual virtual content is integrated into the real world, has been little explored, especially for generating texture sensations. In this paper, we investigate the perception of simultaneous visual and haptic texture augmentation of real tangible surfaces touched directly with the fingertip in AR, using a wearable vibrotactile haptic device worn on the middle phalanx. When sliding on a tangible surface with an AR visual texture overlay, vibrations are generated based on data-driven texture models and finger speed to augment the haptic roughness perception of the surface. In a user study with twenty participants, we investigate the perception of the combination of nine representative pairs of visuo-haptic texture augmentations. Participants integrated roughness sensations from both visual and haptic modalities well, with haptics predominating the perception, and consistently identified and matched clusters of visual and haptic textures with similar perceived roughness.

We present a novel approach for simulating hardness and stiffness using an Encountered-Type Haptic Display (ETHD) with a dynamic end-effector. Addressing limitations in existing haptic rendering methods, our system allows dynamic adjustment of displayed hardness and stiffness. We conducted two experiments to assess users’ perception of virtual blocks’ hardness and stiffness using our device. Results indicate that physical hardness is a more salient feature than rendered stiffness. Evidence of stiffness masking was observed, particularly in high-hardness objects. Regardless of touch method (bare finger or stylus), participants were able to discern hardness and stiffness differences, with users finding it easier to distinguish hardness when tapping using a stylus.