A Soft Touch: Wearable Tactile Display of Softness Made of Electroactive Elastomers

Fingertip-mounted tactile displays of softness are needed for various virtual- or augmented-reality applications such as surgical simulation, tele-operation, computer-aided design, 3D model exploration, and tele-presence. Displaying a virtual softness on a fingertip requires the generation of quasi-static large displacements at moderate forces (as opposed to high-frequency small vibrations at high forces), via a deformable surface, to control both the contact area and the indentation depth of the skin. State-of-the-art actuation technologies are unable to combine simple structure, low weight, and low size, as well as energy efficiency and silent operation. Here, the progress on the development of a non-vibratory display of softness made of electroactive polymers is reported. It consists of a hydrostatically coupled dielectric elastomer actuator, shaped as a bubble interfaced to the fingertip, having a weight of 6 g. Prototypes can generate displacements up to 3.5 mm and forces up to 1 N. By combining this technology with a compact hand tracking sensor, a simple and cost-effective virtual-reality system is demonstrated. A psychophysical study engaging 15 volunteers in poke and pinch tactile tasks shows that users can properly distinguish between different stimuli rendered by the display, with an accuracy correlated to the perceptual difficulty of the tactile comparative task.