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.