Tactile Rendering Using Three Basic Stimulus Components in Ultrasound Midair Haptics
Ultrasound midair haptics (UMH) can present non-contact tactile stimuli using focused ultrasound without any wearables. Recently, UMH has been shown to present not only conventional vibration stimulus but also static pressure stimulus by locally rotating an ultrasound focus at several hertz. Current UMH can present three basic tactile stimuli: static pressure, 30 Hz vibration, and 150 Hz vibration. These primarily elicit responses from three distinct types of mechanoreceptors: SA-I, FA-I, and FA-II. As human texture perception relies on the combination of mechanoreceptor neural responses, this study proposes combining the three basic stimuli to render tactile texture in UMH. Experimental results demonstrate that the proposed method can render at least six discriminable textures with different roughness and friction sensations. Notably, through comparisons with real physical objects, we found that the pressure-only stimulus was perceived as slippery and smooth. The smoothness was similar to a glass marble. When vibration stimuli were synthesized, the perceived roughness and friction increased significantly. The roughness level reached that of a 100-grit sandpaper.