IEEE Trans Haptics. 2022 Apr-Jun;15(2):441-450. doi: 10.1109/TOH.2021.3125843. Epub 2022 Jun 27.
Focused airborne ultrasound provides various noncontact spatiotemporal pressure patterns on the skin. However, the presentation of static force remains an untouched issue because the static radiation force by ultrasound is too weak for the human hand to perceive. Hence, creatable sensations have been limited to vibrations or some dynamically changing feelings. This study demonstrates that a non-vibratory pressure sensation is presented by low-frequency Lateral Modulation (LM) with a fine spatial step width. LM is a pressure modulation method that moves a single ultrasound focus laterally and repetitively along the skin surface. The produced sensation in this study was not perfectly static, but the vibratory perception contained in the stimulus was significantly suppressed under a condition while maintaining its intense perception. We found the condition was 5 to 15 Hz in the LM frequency with a motion step width of less than 1 mm. In a comparison test in the most vibration-suppressed case, the participants reported 0.21 N as an equivalent force to the LM stimulus, significantly higher than the 0.027 N force physically applied by the ultrasound. The statistical analysis also showed that the step width of the LM had a significant effect on its vibratory sensation but not on the intensity of the evoked pressure sensation.
聚焦式空中超声在皮肤上提供各种非接触式的时空压力模式。然而，静态力的呈现仍然是一个未被触及的问题，因为超声的静态辐射力太弱，人的手无法感知。因此，可创造的感觉仅限于振动或一些动态变化的感觉。本研究表明，低频横向调制（LM）可以用精细的空间步宽呈现非振动压力感觉。LM 是一种压力调制方法，可使单个超声焦点沿皮肤表面横向重复移动。本研究中产生的感觉不是完全静态的，但在保持强烈感知的同时，刺激中包含的振动感知被显著抑制。我们发现，在 LM 频率为 5 至 15 Hz、运动步宽小于 1mm 的条件下可以产生这种感觉。在振动抑制最明显的情况下的对比测试中，参与者报告 0.21N 的力与 LM 刺激相当，明显高于超声实际施加的 0.027N 力。统计分析还表明，LM 的步宽对其振动感觉有显著影响，但对诱发的压力感觉强度没有影响。
