Gaseous dichloromethane was irradiated with an electron beam under nitrogen, oxygen, and a mixture of nitrogen and oxygen atmospheres with and without moisture. Experiments using radical scavengers of N2O and cyclohexene showed that the dominant active species that decompose dichloromethane differ depending on the atmosphere. Under dry conditions, N atoms and O-2(-) produced by the irradiation of nitrogen and oxygen oxidize dichloromethane. When moisture is present, the decomposition of dichloromethane by N atoms and O-2(-) is inhibited and OH radicals produced by the irradiation of water decompose dichloromethane. Required absorbed dose for the dichloromethane decomposition strongly depends on the atmosphere.

In social virtual reality (VR) and metaverse platforms, users express their identity through both avatar appearance and on-avatar textual cues, such as speech balloons. However, little is known about how the harmony between these cues influences self-representation and social impressions. We propose that when avatar appearance and text design, including color, font, and tone, are consistent, users experience a stronger self-expression fit and elicit greater interpersonal affinity. A within-subject study (N=21) in VRChat manipulated the social context, color harmony between avatar hair and text, and style or content consistency between tone and font. Questionnaires provided composite indices for perceived congruence, self-expression fit, and affinity. Analyses included repeated-measures ANOVA, linear mixed-effects models, and mediation tests. Results showed that congruent pairings increased both self-expression fit and affinity compared to mismatches, with mediation analyses indicating that self-expression fit fully mediated the effect. These findings integrate theories of avatar influence and computer-mediated communication into a framework for metaverse design, highlighting the value of consistent avatar and text styling.

Food texture perception during mastication involves kinesthetic and somatosensory feedback. However, the somatosensory contributions of intraoral tissues remain poorly characterized as haptic channels. As a preliminary study toward dynamic texture rendering, we conducted psychophysical profiling of electrotactile stimuli at six frequencies $(2-500 ~\text{Hz})$ and three electrode locations. Results suggest that the spatial distributions largely overlapped across electrode locations, whereas perceptual qualities were modulated by stimulation frequency. Stimuli between $10-500 ~\text{Hz}$ tended to be perceived as vibrotactile sensations, while carbonation-like sensations showed a marginal tendency toward higher ratings around 80 Hz.

Humans can perceive the properties of objects outside the body through haptic stimulation, yet it remains unclear whether this ability extends to virtual objects simulated inside the body. In this study, we investigated the ability to estimate the number of virtual objects simulated inside the body based on tactile stimulation alone. We simulated a situation in which the index finger functions as a hollow container containing multiple spherical virtual objects. We computed the physical interactions of virtual spheres colliding with the inner surface of the finger during active finger movements. Using a high density pin array display that enveloped the index finger, tactile stimuli were presented at collision points between the virtual spheres and the finger surface. Through a psychophysical experiment, humans systematically reported higher numerosity as the number of virtual spheres inside the finger increased. Consistent with general characteristics of numerosity judgment, systematic underestimation was observed for larger numerosities. Furthermore, the slope of the response function increased with sphere diameter. This effect could not be explained by participants’ finger movements, suggesting it is likely caused by the stimuli characteristics. These findings shed light on human ability to perceive object properties simulated within the body based on tactile stimulation alone, suggesting the potential of internal body interaction as a novel interaction paradigm.

Touch enables humans to recognize the location, motion, shape, and properties of contacted objects in the real world through mechanoreceptors distributed widely across the skin. However, existing tactile displays typically stimulate only the ventral surfaces of the fingers and hands, limiting the range and richness of touch-based interactions in interactive systems. Here, we present FingerWrap, a high-density pneumatic pin-array display that wraps around the finger and activates the widely distributed mechanoreceptors. FingerWrap uses 337 pins arranged at 13 pins/cm$^{2}$, which cover the ventral, dorsal, and lateral surfaces of the finger up to 45mm from the fingertip, enabling precise spatiotemporal stimulation across continuous regions of the finger skin. Across six perceptual experiments, we show that FingerWrap can provide tactile experiences that ventral-only displays cannot achieve. These include the discrimination of stimulus locations and motion trajectories across multiple regions of the finger skin, the recognition of three-dimensional shape features, and the perception of realistic resistance when the finger is immersed in virtual liquids. This display, which enables a rich and realistic touch experience, could serve as a platform for exploring novel tactile interactions and basic scientific research.

Haptic feedback, which enhances operability and realism, is extensively employed in smartphones and controllers. One notable tactile presentation method involves the use of visual stimuli to evoke tactile sensations, exemplified by the concept of pseudo-haptics. In these methodologies, resistance and force are simulated by modulating the velocity of the avatar’s finger or the operation pointer. Currently, there exists a discrepancy between the user’s inherent sensory perception and the visual information presented. In this study, we propose a novel approach to modifying the perception of tactile stimulation by concurrently presenting an onomatopoeic word with the tactile stimulus. For the experiment, we developed a smartphone application that, upon tapping a displayed button, triggers both a vibration stimulus and the presentation of an onomatopoeic word that conveys a sense of touch and sound. We employed six switches with varying tactile sensations to evaluate whether the user’s perception would be influenced by the type of onomatopoeia displayed in the application. The experimental results demonstrated that five onomatopoeic words elicited distinct tactile sensations. Additionally, we observed that four of these words enhanced the perceived realism of the button-press sensation. This method diverges from existing techniques by altering the tactile perception through visually presented linguistic information. Although this approach is constrained to scenarios where the haptic object is within the visual field, it is straightforward to implement and can be readily applied to existing smartphones and virtual reality devices.

While the relative motion between the skin and objects in contact with it is essential to everyday tactile experiences, our understanding of how tactile motion is perceived via human tactile function is limited. Previous studies have explored the effect of normal force on speed perception under conditions where multiple motion cues on the skin (spatiotemporal cue, tangential skin deformation cue, and slip-induced vibration cue) were integrated. However, the effect of the normal force on speed perception in terms of each motion cue remains unclear since the multiple motion cues have not been adequately separated in the previously reported experiments. In this article, we aim to elucidate the effect of normal force in situations where the speed perception of tactile motion is based solely on a spatiotemporal cue. We developed a pin-array display which allowed us to vary the intensity of the normal force without causing tangential forces or slip-induced vibrations. Using the display, we conducted two psychophysical experiments. In Experiment 1, we found that the speed of the object was perceived to be 1.12-1.14 times faster when the intensity of the normal force was doubled. In Experiment 2, we did not observe significant differences in the discriminability of tactile speed caused by differences in normal force intensity. Our experimental results are of scientific significance and offer insights for engineering applications when using haptic displays that can only provide spatiotemporal cues represented by normal forces.

Augmented Sports is a new type of sport that combines existing physical sports with virtual parameters (VPs), which are commonly used in video games. Integrating VPs has great potential to improve players' performance in playing sports. Therefore, a sophisticated VPs design is necessary to achieve enjoyable Augmented Sports. In this study, we developed a new Augmented Sport called "Parablade," an extension of Chambara. In this paper, we introduce the details of Parablade and propose a novel method of designing VPs to achieve an appropriate game balance.

In metaverse environments, we test whether visual harmony between avatar appearance and text design shapes trait impressions. Using a within-subject design that manipulates avatar hair color and text color/font, we find that congruent pairs increase satisfaction and affinity and convey traits more consistently, informing design guidelines for expressive communication.

This study presents a novel contact detection system for "Parablade," a chambara-based, sword-play augmented sport. Augmented sports combine physical activities with virtual parameters (VPs) to create a balanced and equitable gaming experience, irrespective of players' physical capabilities. The proposed Parablade Microphone Unit (PMU) employs multiple micro-phones and machine learning algorithms to detect and classify hit events through sound recogni-tion. This system aims to ensure real-time updates of VPs, thereby enhancing the gameplay expe-rience. Experimental results indicate that the PMU can accurately recognize the occurrence and location of hit events with a high accuracy rate of 93.33 generated from the sword.

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^∘ 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.

In orthodontic treatment for children, a method has been recommended to strengthen bite force by chewing a tube in a certain rhythm for five minutes every day. However, ensuring that children keep the training daily is difficult due to repetitive, monotonous movements. Additionally, it is not easy for guardians to keep monitoring and ensure that children are doing the training properly, biting the tube with appropriate force. Therefore, we aim to develop an interactive serious game that utilizes bite force as an input device, allowing children to continue training properly and allowing guardians to monitor their training situation easily. This study introduces a simplified tube-based bite force measurement device to assess and record the force of the bites, as well as training games using the device.

Telekinesis is the ability to manipulate remote objects without direct physical contact. In fictional works, telekinesis users are often depicted as controlling objects with their hands and other body parts as if by will alone. Such depictions suggest that users experience a sense of agency over the object despite not physically touching it. In this study, we developed a VR method to simulate telekinesis and investigated whether it is possible to achieve a sense of physical sensation and agency similar to the experience portrayed in fiction.

Representing tangential motion between objects and the skin using tactile displays enables humans to manipulate virtual objects and recognize their surface properties. To design effective tactile stimuli that accurately represent motion, it is important to understand how humans perceive tactile motion based on spatiotemporal features, an area that remains relatively unexplored. This study elucidates the spatiotemporal features that influence the perceived speed of tactile motion represented by a tactile display with discrete stimulation points. The findings show that the average spatial spacing between stimulation points affects the perceived speed, even though the average spatial spacing does not vary with the speed itself, but rather varies with the stimulation point layout of the tactile display. No significant effects from other features were observed on the perceived speed. The results suggest that perceived speed can be controlled by considering the average spatial spacing during tactile stimulus design.

This study investigated vibrotactile spatiotemporal pattern recognition in the two-dimensional space around a hand. The participants placed their hands on the medium, and identified the recognized pattern presented in the medium. There were 64 rotational patterns, presented with sequential impulse vibrations. We investigated how well humans recognized the patterns presented around their hand, and identified the pattern factors (e.g., rotational direction) that affected recognition accuracy. The probability of obtaining correct answers was 48.9 %. It was observed that the start and end points, rotational direction, and the number of vibrations affected recognition accuracy. It was also found that patterns starting or ending on the ulnar side ( $0^{\circ }$ ) of the hand were difficult to recognize, whereas those starting or ending on the distal ( $90^{\circ }$ ) or proximal side ( $270^{\circ }$ ) of the hand were easily recognizable. Furthermore, we found a type of the oblique effect. Patterns starting or ending in the oblique direction were more difficult to recognize than those in the cardinal direction. We also found that the clockwise rotational pattern was slightly easier to recognize than the counterclockwise rotational pattern. Finally, the underestimation of the judgment of tactile numerosity explains how the number of vibrations in the patterns affected the recognition accuracy. This result can be used as a baseline when the recognition of spatiotemporal patterns outside the body under other conditions is examined in future studies.

The tactile information to be presented to a user during interaction with a virtual object is calculated by simulating the contact between the object model and user model. In the simulation, a distributed force is applied to the contact area on the skin tissue of users' hands and results in deformation of the skin tissue. The skin deformation caused by the distributed force is the target contact state that should be presented by the device. However, most multipoint haptic displays do not have sufficient degrees of freedom (DoF) to represent the target contact state. This paper presents the concept and formulation of "deformation matching," whereby the output force is calculated to minimize the error between the target skin deformation and skin deformation that can be realized by the limited DoF device's output force. For comparison, the conventional concept of "force matching" was also formulated. The difference in human perception between these two concepts in the expression of friction was investigated through experiments using a pin-array tactile display capable of stimulating 128 points. It was demonstrated that the perception of the friction coefficient was more sensitive and the perception of the friction direction was more accurate in deformation matching than in force matching.

Kemo-mimi means the dog- or cat-like ears on a humanoid character, or the ears of the animal itself. Kemo-mimi is often used as an element of the avatar’s appearance. It is generally considered that the posture of animal ears represents the animal’s emotional state. And the idea has been used as a technique for expressing emotions in many cartoon and animation works. But despite this fact, there are few examples of studies on the emotions that can be expressed by animal ears. Therefore, we decided to investigate the relationship between the posture of the animal ears and emotions and to establish a method of expressing emotions using the ears. In the experiments, three-dimensional animations of animal ears changing posture were presented to the subjects, and they were asked to answer the emotion corresponding to the posture. The results showed that there was a certain degree of a common understanding of people’s impressions concerning the animal ears. In this paper, we report the emotions that can be expressed by the posture of the animal ears as revealed in this study.

Previously, tactile displays focused on the tactile presentation of the surface of a virtual object. In contrast, this study attempts to provide a tactile feeling on the space inside a virtual object when fingers penetrate it. Our previous study developed a finger-mounted pin-array display with the smallest pin pitch, representing the highest spatial resolution. Using the display, we attempt to present the tactile impression of "Rough," "Grainy," and "Sparse" which correspond to Japanese onomatopoeia of "Zara-Zara," "Tsubu-Tsubu," or "Chiri-Chiri" with simple patterned stimuli arranged in 3D space. A series of experiments were conducted in this study to determine the following: (1) the stimuli that can provide users with different tactile impressions inside objects and (2) the effect of tactile display spatial resolution on the recognition of tactile impressions inside objects. The results clarified that we could provide three different tactile impressions in space with certain stimuli configurations. Besides, the results demonstrated that participants recognized the tactile impression better with a larger spatial resolution configuration of the device. This study reveals a new field of tactile presentation, that is, tactile presentation inside an object.

It is difficult for recreational players to continue practicing sports, which they know is important to improve their technique and get more enjoyment. Therefore, we propose utilizing a concept of “toolification of games”, which enables players to perceive the effect of practicing while playing a game. Few papers have focused on sports training while playing a video game, but some sports players benefit from a training strategy similar to playing particular video games. This benefit suggests the possibility of using a video game for sports training. The proposed method will contribute to making monotonous training more enjoyable by “improving their sports skill while playing a game.” In this study, we focused on badminton training and playing Tetris together. When practicing badminton, the player is often required to hit the shuttlecock to different parts of the court anywhere they want to. This way of practicing is similar to a general strategy used when playing Tetris—the player attempts to distribute Tetriminos (block units in the Tetris game) to every row without bias. This paper describes experimental results from badminton training practice using Tetris compared with practice using conventional visual feedback methods.