Cooling feedback has been shown to improve user experience in virtual reality. However, many existing methods face limitations, such as requiring skin contact, relying on airflow, having bulky components, or delivering unstable sensations. These issues limit their applicability to wearable systems, especially in scenarios demanding high responsiveness and perceptual consistency. We propose ChillFactor, a highly responsive, non-contact cooling interface for head-mounted displays (HMDs). It uses ultrasonic atomization of a predetermined alcohol solution to generate evaporative cooling near the skin, reducing airflow-induced artifacts and providing relatively consistent cold sensations. To validate the design, we first evaluated the system's cooling performance. At maximum output, it lowered skin temperature by approximately 2.6 °C within five seconds, a rate sufficient to induce an almost immediate perception of cold. We subsequently integrated ChillFactor into an HMD and conducted a user study with 12 participants in immersive VR scenarios. Participants reported perceiving the cold within 0.66 seconds and noted significantly higher levels of presence and realism compared to conditions without cooling feedback, demonstrating the system's effectiveness in enhancing immersion through rapid and adjustable thermal cues. This work provides a practical foundation for non-contact cooling feedback and expands the design space for multisensory interaction in virtual environments.

Although a variety of haptic devices are used for virtual reality (VR) and augmented reality (AR) experiences, few can present a wide range of softness-hardness of the surface of the virtual objects. We propose a haptic device that can present a wide range of softness-hardness by using a two-layered structure consisting of a pneumatic balloon and a mechanical piston. Through a series of user studies, we confirmed that the prototype can present five levels of softness and three levels of hardness, and that the prototype device improves the VR experience in terms of realism, enjoyment, and comfort for virtual objects with a variety of softness/hardness.

Most existing locomotion devices that represent the sensation of walking target a user who is actually performing a walking motion. Here, we attempted to represent the walking sensation, especially a kinesthetic sensation and advancing feeling (the sense of moving forward) while the user remains seated. To represent the walking sensation using a relatively simple device, we focused on the force rendering and its evaluation of the longitudinal friction force applied on the sole during walking. Based on the measurement of the friction force applied on the sole during actual walking, we developed a novel friction force display that can present the friction force without the influence of body weight. Using performance evaluation testing, we found that the proposed method can stably and rapidly display friction force. Also, we developed a virtual reality (VR) walk-through system that is able to present the friction force through the proposed device according to the avatar's walking motion in a virtual world. By evaluating the realism, we found that the proposed device can represent a more realistic advancing feeling than vibration feedback.

Force feedback in tool-mediated interactions with the environment is important for successful performance of complex tasks in our daily life as well as in specialized fields like medicine. Stylus-based haptic devices are studied and used extensively, and most of these devices require either grounding or attachment to the body of the user. Recently, non-grounded haptic devices are getting an increasing attention. In this paper, we propose a novel method to represent the vertical forces that are applied on the tip of a tool: a non-grounded rotation mechanism that mimics the cutaneous sensation that is caused by these tool-tip forces. To evaluate this method, we developed a novel ungrounded haptic device - HapSticks - that renders the sensation of manipulating objects using chopsticks. First, we present the novel mechanism, and test the pressure that it applies on the hand of the user when rendering a force at the tip of the tool in comparison to applying a real force at the tip of the tool. Next, we used the mechanism to build the HapSticks device as an example of an application of the proposed method, and present a psychophysical evaluation of this device in a virtual weight discrimination task.

This research aims at constructing an intrinsic tactile interface for ubiquitous haptic AR. In order to avoid obstruction of natural object manipulation with the fingertip, we focused on electrotactile interface. We proposed a time division multiplexing technique with compensating processes allowing detection and augmentation of touch feeling through shared electrodes. In this paper, we investigated the performance as a sensor and display by a pressing task. First, we obtained an optimized parameter for the multiplexing. Next, the stimulus effect on the sensor performance was tested. Finally, we confirmed that the proposed interface has a potential to modulate user's cutaneous feeling.

The fine concavo-convex shape of the object surface is a critical component that determines its texture. A previous electrotactile display could not tactually present fine concavo-convex objects but only a line pattern on the plane. In this study, the authors proposed a physiology-based tactile mapping method by formulating nerve activities that stem from a mechanical stimulus. The proposed electrical stimulus allows a human to perceive a concavo-convex shape. A stimulus frequency coded the skin displacement given by a concavo-convex shape and represented the adaptation of receptors with exponential approximation. As an example of tactually presenting a concavo-convex shape, roughness was introduced by using a Brownian surface, which enables a user to touch a surface of varying degrees of roughness with a developed tactile display mounted on a computer mouse. The results of subjective experiments showed a statistical difference among the perceived roughness of displayed rough surfaces. This study concluded that the proposed tactile mapping method was effective to present a touch sensation for concavo-convex shapes corresponding to a stimulus frequency below 100 Hz.

Most of the materials in the world absorb and diffuse liquid through their bodies. Porous media is a material that has internal pore space and is able to absorb liquid, such as a sponge or soil. Liquid flow of the porous media has been intensively studied in geotechnical engineering. However, previous studies never considered the elasticity change by the portion of liquid in the porous media. Liquid absorbed by the porous media affects the elastic property of the porous media and, hence, its behavior. This study proposes a model including the elasticity change of the porous media by liquid flow.