Electro-tactile Display: Principle and Hardware

Abstract

An electro-tactile (electrocutaneous) display is a tactile display that directly activates sensory nerves in the skin by electrical current supplied from an electrode on the skin surface. Compared with a mechanical tactile display that is typically composed of vibrating pins, the electro-tactile display has several merits, such as thinness and mechanical robustness. However, there remain several issues to be solved, such as stabilization. Furthermore, the development of the electro-tactile display requires certain knowledge of electrical circuits. The present paper thus serves as an introduction to research on electro-tactile displays. We start by explaining the principle of electrical nerve stimulation, introducing how the spatial distribution of the electrical current source affects stimulation using the notion of the activating function, and discuss temporal parameters (i.e., pulse width and pulse height) using a simplified nerve model and introducing the strength-duration curve. A typical hardware design, including a voltage-to-current converter circuit and a switching circuit is then introduced, and the electrode fabrication process and necessity of a conductive gel layer are discussed. Finally, the issue of sensation stabilization is treated with possible solutions.