A tactile display is a human-computer which uses the sense of tactation. Tactile displays can reproduce as closely as possible the tactile parameters of an object, such as shape, surface texture, roughness and temperature. Tactile displays have been proposed as an interface in Virtual Environment (VE)–Virtual Reality (VR) applications and as feedback in teleoperation. Additionally they are used as a complement or substitution of the visual presentation of information, and for tactile communication in mobile environments.
Tactile sensations are perceived via mechanoreceptive units, embedded in the outer layers of the skin, which when activated transmit signals to the brain. By stimulating the human skin to induce tactile perception, tactile displays provide an important alternative of information transmission. The tactile channel may be used by people with vision or hearing impairments or in cases where the other sensory channels are saturated. Such tactile stimulation can be accomplished in various technologic ways. Solutions based on mechanical needles actuated by electromagnetic technologies (solenoids, voice coils), piezoelectric crystals, shape memory alloys, pneumatic systems, and heat pump systems based on Peltier modules have been proposed. Other methods, such as using electrorheological ﬂuids (ERF) and magnetorheological ﬂuids (MRF), which change viscosity and therefore rigidity under the application of an electric or magnetic ﬁeld, respectively, are still under investigation. On the other hand, technologies dedicated to medical applications, such as electrotactile and neuromuscular stimulators, have not yet been used because of their invasive nature. The methodology used in VE systems was inspired from matrix pin-printer technologies and Braille systems for the blind. In order to present refreshable two-dimensional tactile patterns, a tactile display with a large number of identical but individually addressable tactile stimulators is desirable, especially when used for sensory substitution for the visually impaired community.
Among various tactile displays that are pneumatically, magnetically, thermally, or piezoelectrically driven, electro-tactile displays have the advantages of simple structures, low power consumption, and low cost when the number of stimulators increases. Furthermore, micromachining may be employed to fabricate high-density electrotactile stimulator arrays with the potential of further cost reduction and miniaturization.