A novel electrotactile display that can be integrated into current handheld devices with touch screens is presented.
In this display, tactile information is presented to the fingertip of the user by transmitting small currents through electrodes.
A special transconductance amplifier keeps the current stable, independent of moisture of the skin.
An electrotactile display system consisting of two layers was implemented for the augmentation of tactile sensations.
The first layer is an optically transparent electrode that is placed on the touch screen (i.e., the front side of a handheld device). The second electrode is an electrically conductive part or coating, which can be the metal rear panel of the device. If the user holds the device in his hand, he has a large-area contact with the metal rear panel.
If he now contacts the touch screen with his fingers, a local electric current passes through the skin, and the subcutaneous potential distribution excites the mechanoreceptors.
Experiments were conducted to investigate the perception of simulated textures using this electrotactile display technique. One fundamental feature of texture 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 if 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.
Want to know more? A detailed discussion and experimental data can be found in the following publications.