Interpersonal Vibrotactile Feedback via Waves Transmitted through the Skin: Mechanics and Perception

Interpersonal touch is critical for health, development, and social relationships. An emerging opportunity in haptics is to design methods for augmenting interpersonal touch. Recently, we presented an actuated smart bracelet for transmitting vibrations through the hand of one person, as feedback to the hand of a second person, during a social interaction such as a handshake. Here, we present an investigation of human factors of vibrotactile feedback provided between people. In two experiments, we studied mechanical transmission of vibrations through a first person (the transmitter) and the perception of these vibrations by a second person (the receiver) who is touching the transmitter’s hand. We found that a receiver could readily perceive vibrotactile feedback when touching different locations on the transmitter’s hand. The magnitude of the transmitter’s skin acceleration was highly correlated with intensity the receiver perceived (Pearson’s R = 0.737). We found both perception and mechanics to depend on the driving signal characteristics and the direction in which the transmitter’s skin was actuated (at the wrist) to produce the vibrations. Low-frequency vibrations (50 and 100 Hz) were more readily perceived than higher frequencies (200 Hz). Vibrations produced by normal-direction actuation elicited perceptual responses that were less variable than those produced by tangential actuation. In addition, vibrations produced by tangential actuation at the wrist were felt to be very strong when a receiver touches the palm or base of the transmitter’s hand, but were felt to be weaker near the transmitter’s fingers. This study elucidates human factors for vibrotactile feedback between two people, and holds implications for the design of haptic technologies for the augmentation of interpersonal touch.