Spatiotemporal Haptic Effects from a Single Actuator via Spectral Control of Cutaneous Wave Propagation

A key challenge in haptic engineering is to design methods for stimulating the skin - a continuous medium with infinitely many degrees of freedom - via practical devices with few degrees of freedom. Here, we show how to use a single actuator to generate tactile stimuli with dynamically controlled spatial extent. The method is based on the frequency-dependent damping of propagating waves in the skin. We use full-field optical vibrometry to show that vibrations introduced at the fingertip elicit waves in the finger that propagate proximally toward the hand. We show that these waves travel distances that decrease rapidly with frequency. We demonstrate the utility of these results by designing haptic effects that produce wave fields that expand or contract in size, and that can be delivered via a single actuator. In a perception experiment, subjects accurately (median >95%) identified these stimuli as expanding or contracting without prior exposure or training. These findings demonstrate how the physics of waves in the skin can be exploited for the design of spatiotemporal tactile effects that are practical and effective.