F5-4　Study on Haptic Texture of Buttons for User Interfaces

Abstract

Haptic textures can be used as a haptic cue to help users choose the correct buttons. However, the images of the button's function created by touching a haptic texture depends on factors such as the user's knowledge, experience, context, etc. Therefore, the aim of this study is to determine the characteristics of anisotropic haptic textures used on the surface of paired buttons through an experiment. In the experiment, we used shark skin as an anisotropic material for the buttons. The riblet grooves on the shark skin are aligned from head to fluke; thus, most people would feel the strongest friction by rubbing the surface of the shark's flank skin toward the direction of the fluke.Therefore, wedefined the direction from head to fluke as the directional criteria of the shark skin. To measure the objective and subjective frictional force of the shark skin, a rubbing tester and the forefinger of the dominant hand of 30 young individuals were used. All participants pointed out that they felt the anisotropic haptic texture by rubbing the shark skin. Over 27 participants created a directional image in which the button suggested antidirectional criteria, which most of the participants felt very smooth to touch. The frictional coefficient in the direction of anticriterial was the significantly lower. Based on the results of participants' directional image, we evaluated the effectiveness of the haptic texture on the paired buttons. In the evaluation experiments, 60 participants tried to choose the button that controls the front fog lamp of a car from similar paired buttons by touching them from above. The buttons were arranged from right to left on a switch box, and had symbols to indicate whether they were for the front or rear fog lamps. The participants were divided intotwo groups of thirty participants each. For group 1, the paired buttons had similar haptic textures, while for group 2 the paired buttons had oppositely-oriented haptic textures. From the percentage of correct answers given by the two groups, the participants in group 2 gave more correct answers than those in group 1, although they did not know about the symbols attached to the buttons indicating the front and rear fog lamps. Therefore, we concluded that the anisotropic haptic texture of paired buttons could suggest directional image to the user and add a cue for choosing the paired button correctly.