Mid-Air Tactile Stimulation Using Indirect Laser Radiation

Abstract

In this paper, we demonstrate that a laser irradiated on a thin light-absorbing elastic medium attached on the skin can elicit a tactile sensation of mechanical tap. First, we present simulation results that show laser irradiation to the elastic medium creates inner elastic waves on the basis of thermoelastic effects and these elastic waves trigger the bending deformation of the medium, which then stimulates the skin. Second, we analyze the physical properties of the associated stimulus by measuring its force profile. Third, we identify the perceptual characteristics of the stimulus in comparison to those of mechanical and electrical stimuli by means of a perceptual experiment employing dissimilarity rating. All the evidence indicates that indirect laser radiation provides a sensation of short mechanical tap. Furthermore, little individual difference was observed in the results of the perceptual experiment. To the best of our knowledge, this study is the first in reporting the feasibility of indirect laser radiation for mid-air tactile rendering.

Mid-Air Tactile Sensations Evoked by Laser-Induced Plasma: A Neurophysiological Study

“…Laser can be focused on a distant location with high precision from a remote source as long as ∼10 m. Such long-distance stimulation can overcome limitations of current ultrasonic or air jet mid-air stimulation technologies (Gwilliam et al, 2013;Jun et al, 2015;Kim et al, 2015;Ismo et al, 2020;Yang et al, 2021). Also, tactile stimulation using laser-induced plasma does not require an explicit elastic medium attached to the skin as in the previous study (Singh et al, 2014;Lee et al, 2016), making itself available to more general applications. This mid-air tactile sensation using the laser-plasma phenomenon has to consider two distances.…”

“…Hence, our followup study will verify psychophysical studies on the perception of laser-induced plasma tactile stimuli as well as subjective reports of more precise description of the type of tactile sensations they evoke. Additionally, we did not examine the effect of various laser parameters on neural responses and perception, such as pulse energy, repetition rate, and pulse width (Lee et al, 2016). We will investigate whether laser-induced plasma stimulation can deliver different tactile sensations through parameter adjustment.…”

“…Alternatively, laser can overcome such shortcomings with a relatively long energy travel distance if it is possible to evoke tactile sensation using laser. Recent work by our research group has proven that a thermoelastic effect induced by direct laser pulse irradiation to the skin indeed evokes tactile sensation in humans (Lee et al, 2015(Lee et al, , 2016. In this work, a physical experiment followed by perceptual and neurophysiological experiments to evaluate human perceptual and neural responses to laser-induced tactile stimulation revealed that innocuous tactile sensation was reportedly perceived along with eventrelated (de)synchronization [ER(D)S] of sensorimotor rhythms (SMRs) of electroencephalography (EEG) that typically reflects tactile sensory information processing (Long et al, 2014;Sho et al, 2019).…”

“…A simulation study suggested that instantaneous absorption of a laser pulse generates transient bending stress, which in turn causes deformation and vibration of the elastic medium. The study demonstrated that humans could perceive a tactile sensation similar to a short tap on the finger in response to the indirect laser irradiation (Lee et al, 2015(Lee et al, , 2016.…”

Multichannel Ultrasound Focusing Delay Control Method Based on Variable-Length Shift Register for Airborne Ultrasound Tactile Feedback

“…However, using this method, it is difficult to accurately control the air flow, and the tactile resolution is low; thus, detailed tactile feedback cannot be provided. Another method uses a photoelastic material to convert irradiated laser light into vibrotactile stimuli, so it is a contact method [6]- [8]. The main drawback of this method is that its optical structure is complex, so it can be easily blocked, and the laser may burn the user's skin.…”