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 as a physical stimulation is limited in modality and is uncommon in the natural world. In many cases, for human-robot and human-human interaction, a more natural, affective tactile interaction is needed to provide comfortable and varied stimuli. In this letter, we present the super-cutaneous wearable electrical empathic stimulator (SCWEES), a tactile device that gently stretches and squeezes the surface of the skin. Our hypothesis is that this device can create a pleasant, unobtrusive sensation that can be used to mediate social interactions or to deliver subtle alerts. We describe 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: stimulation strength and pleasantness, contraction and extension, and the conveyance of non-disruptive notifications. Quantitative and qualitative results show that the SCWEES generates a pleasant sensation, can convey useful information in human-machine interactions, and delivers affective stimulation that is less disruptive than conventional vibratory tactile stimulation when the user is engaged in a task.