A wearable skin-stretching tactile interface for human-robot and human-human communication

Currently, the majority of wearable robotic haptic feedback devices rely on vibrations for relaying sensory information to the user. While this can be very effective, vibration is a limited physical stimulation, appearing rarely in the natural world. In many cases of human-robot and human-human interactions, a more natural, affective and effective tactile interaction is needed to provide well-rounded and varied stimuli. In this work we present the Super-Cutaneous Wearable Electric Empathic Stimulator (SCWEES), a tactile device that gently stretches and squeezes the surface of the skin. Our hypothesis is that this device creates a pleasant, unobtrusive sensation that can be used to mediate social interactions or for delivering subtle alerts. We present the design of the SCWEES, a lightweight 3D printed semi-flexible structure that attaches to the skin at two points and actuates via two shape-memory alloy coil actuators. We evaluate the SCWEES through a range of human interaction experiments. These include evaluation of stimulation strength and pleasantness, compression and expansion, and ability to convey non-disruptive notifications. Quantitative and qualitative results show that the SCWEES generates a pleasant sensation, can convey useful information in human-machine interactions, and its affective stimulation is less disruptive than conventional vibratory tactile stimulation when the user is engaged in a task.