Objective Evaluation of Tactile Sensation for Tactile Communication

We humans use the five senses of “sight, sound, touch, taste and smell,” to interact with other people and various objects around us. While remote communication with video and speech have become familiar to us lately, DoCoMo is currently working on research aiming at finding ways to communicate via tactile sensation, which is believed to be important in terms of information volume, which comes after sight and sound. By using various functions that tactile sensation has, new application fields that have not been achieved with conventional communication media only can be expected to appear in the near future. In physiology, tactile sensation is called somatic sensation; it is classified into “deep sensation” caused by such as subdermal muscles, tendons, joints, and “cutaneous sensation” caused by receptors on the surface of the skin [1]. Deep sensation is caused by receptors existing in joints, and muscles, and provides motion-related information such as position sensation, sensation of speed and haptic sensation. Cutaneous sensation refers to the sense of touch perceived by the surface of the skin, such as the “harsh” or “smooth” feel of a fabric. This article focuses on cutaneous sensation. DoCoMo has been carrying forward research on tactile displays using electrical stimulation [2]. By stimulating nerves connected to tactile receptors electrically, the firing of the tactile receptors can be reproduced and tactile sensation can be represented artificially. For example, tactile sensation felt when stroking an object is perceived through the following process: the fingers’ “shapes are deformed” due to contact with “the surface shape,” whereupon the “tactile receptors fire due to the finger shape deformation (launch of nerve impulse),” and “tactile sensation is felt when the signals are received and processed by the brain.” There are many unresolved mechanisms involved in the human cognitive processes, and in order to construct a functioning tactile display, it is necessary to understand the process from “surface shape” to the “firing of tactile receptors due to finger shape deformation.” For this reason, we focused on simulation of finger shapes deformation in this contract research. By obtaining quantitative indexes for “how should stimuli be presented to reproduce certain tactile sensations,” our research will be able to take a big step forward toward realization of tactile communication.