Combination of cathodic electrical stimulation and mechanical damped sinusoidal vibration to express tactile softness in the tapping process

A damped sinusoidal vibration is generally used to reproduce the sensation of tapping. However, the type of actuator generally used in the field of tactile display cannot produce very low-frequency vibrations, and thus cannot activate Merkel cells to produce the sensation of cutaneous pressure. In this study we propose a method that combines cathodic electrical stimulation, which produces a pressure-like sensation, with a mechanical damped sinusoidal vibration. Our experiment demonstrated that the cutaneous pressure sensation produced by cathodic electrical stimulation mostly affects the perception of softness, allowing our method to reproduce sensations of softness/hardness over a wider range than when using mechanical vibration alone. Most participants felt that the combination of these two stimulations provided a more realistic tapping sensation.