This study investigates how sinusoidal surface patterns applied to cylindrical grips influence haptic impressions during comfort grasping. Thirteen samples were prepared by combining four wavelength levels and three amplitude levels of sinusoidal profiles on a 150-mm-long, 30-mm-diameter cylinder, along with a flat control grip. Twelve participants grasped each sample with one hand and rated seven questionnaire items-painfulness, hardness, smoothness, softness, ease of grip, force applicability, and comfort- using a nine-point scale. A repeated-measures analysis of variance showed significant main effects of sample type for all items, indicating that both grip profiles modulated impressions. To clarify the underlying perceptual structure, principal component analysis (PCA) was performed on z-standardized ratings averaged across participants. The PCA biplot revealed two nearly orthogonal bundles of loadings: one contrasting “painful” with “smoothness” and “ease of grip,” and another contrasting “hardness” with “softness,” “comfort,” and “force applicability.” These bundles represent two independent axes of perceptual variation induced by sinusoidal profiles-one related to discomfort versus smooth feel, and the other related to hardness versus soft and comfortable grip feel.
WATANABE et al. (2026) studied this question.