Electrotactile Feedback for Handheld Devices with Touch Screen and Simulation of Roughness

We present a novel electrotactile display that can be integrated into current handheld devices with touch screens. In this display, tactile information is presented to the fingertip of the user by transmitting small currents through electrodes. Experiments were conducted to investigate the perception of simulated textures using this electrotactile display technique. One fundamental feature of texture, which is the focus of this study, is roughness. The aim of the first experiment was to investigate the relationship between electrotactile stimulation parameters such as current and pulse frequency and the perception of roughness. An increase in the current magnitude resulted in an increase in perceived roughness. The aim of the second experiment was to investigate parameter combinations of electrotactile stimuli can be used to simulate textures. Subjects adjusted the intensity and frequency of the current stimuli until the simulated textures were perceived as being equal to reference textures such as sandpapers of varying grit numbers and grooved woods with varying groove widths. Subjects tended to find an electrotactile stimulus with a high current magnitude and a low pulse frequency more suitable to represent rough surfaces. They tended to find just-perceptible current magnitudes suitable for very smooth surfaces and did not show a preference for any frequency.