ambienBeat - Wrist-worn Mobile Tactile Biofeedback for Heart Rate Rhythmic Regulation.

We present a wrist-worn mobile heart rate regulator -- ambienBeat -- which provides closed-loop biofeedback via tactile stimulus based on users' heartbeat rate (HR). We applied the principle of physiological synchronization via touch to achieve our goal of effortless regulation of HR, which is tightly coupled with mental stress levels. ambienBeat provides various patterns of tactile stimuli, which mimics the feeling of a heartbeat pulse, to guide user's HR to resonate with its rhythmic, tactile patterns. The strength and rhythmic patterns of tactile stimulation are controlled to a level below the cognitive threshold of an individual's tactile sensitivity on their wrist so as to minimize task disturbance. Here we present an acoustically noise-less soft voice-coil actuator to render the ambient tactile stimulus and present the system and implementation process. We evaluated our system by comparing it to ambient auditory and visual guidance. Results from the user study shows that the tactile stimulation was effective in guiding user's HR to resonate with ambienBeat to either calm or boost the heart rate using minimal cognitive load.