Directional Vibration Sensitivity of the Finger for Haptic Feedback Switch Design

Haptic switches use controlled vibration feedback to emulate realistic operational sensations. While frequency effects are well-documented, research on the combined influence of pressing force and vibration direction remains limited. This study investigates how fingertip force modulates directional vibration sensitivity across spatial axes. Using a staircase 2AFC paradigm, participants evaluated 125 and 250 Hz sinusoidal stimuli under 1, 3, and 5 N pressing forces in orthogonal (Z) and tangential (X, Y) orientations. Results indicated a significant main effect of frequency, with sensitivity being superior at 125 Hz. Additionally, pressing force significantly modulated perception; overall sensitivity peaked at a minimal 1 N and generally declined as applied force escalated to 3 N and 5 N. These findings aim to establish design guidelines for haptic switches tailored to diverse operational forces.