Wearable Tactile Display Based on Thermal Expansion of Nichrome Wire

A wearable tactile display needs to be compact and lightweight, and ideally should be able to present vibration, force, and temperature information to the hand. In many contexts spatially distributed tactile information is needed such as when identifying the shape of objects. In this paper, a multi-element tactile display is described based on the thermal expansion and contraction of nichrome wire. The device comprises elastic rods that are pulled by nichrome wires (30 μm in diameter). When an electrical current is applied to the wire, displacement of the elastic rod occurs with thermal elongation of the wire. The wire cools quickly and vibration results. The nichrome wire that is the basis of this display overcomes many of the material restrictions associated with shape memory alloys that have often been used for thermally driven tactile displays. Experiments that characterized the performance of the tactile display indicated that perceptible vibrations up to 320 Hz can be presented. Psychophysical studies revealed that both position and movement cues can be displayed effectively with the device. A miniaturized version of this display for wearable applications has been built and undergone preliminary evaluation.