We present a mobile heart rate regulator—ambienBeat—which provides closed-loop ambient biofeedback via subliminal tactile stimulus based on a user's heartbeat rate variability (HRV). We applied the principle of interpersonal physiological synchronization to achieve our goal of effortless regulation of HRV, which is tightly coupled with mental stress levels. ambienBeat provides various patterns of subliminal tactile stimuli, which mimics the feeling of a heartbeat pulse, to guide a user's HRV 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 noiseless, 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 subliminal tactile stimulation was effective in guiding a user's HRV to resonate with ambienBeat to eith… View full description
We present a mobile heart rate regulator—ambienBeat—which provides closed-loop ambient biofeedback via subliminal tactile stimulus based on a user's heartbeat rate variability (HRV). We applied the principle of interpersonal physiological synchronization to achieve our goal of effortless regulation of HRV, which is tightly coupled with mental stress levels. ambienBeat provides various patterns of subliminal tactile stimuli, which mimics the feeling of a heartbeat pulse, to guide a user's HRV 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 noiseless, 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 subliminal tactile stimulation was effective in guiding a user's HRV to resonate with ambienBeat to either calm or boost the heart rate using minimal cognitive load.
By reading the distance between the peaks of the heart beat pulse (R-R interval), we can continuously estimate the changing HR, and derive a great deal of information about our cardiovascular state, mood, stress levels and anxiety. For this reason, one technique to regulate mental state is tightly coupled with cardiovascular afferents, which have numerous connections to multiple areas of the brain, and play an important role in determining emotional experience [1]. Meditation is a form of mental training that has been practiced for thousands of years. It can be considered to be part of the family of complex emotional and attentional regulatory training regimens developed for various ends, including the cultivation of well-being and emotional balance [2]. Practicing meditation incorporates attention to internal body sensations.
Mindfulness [E. J. Langer, 1989], which refers to a mental state of being conscious or aware of one's present moment, and accepting feelings, thoughts, and bodily sensations, has been called the ”heart” of Buddhist meditation. Over the past 20 years, researchers have focused on evaluating the effects of mindfulness on stress reduction [J. K. Zinn et al., 2009] through clinical tests and validated its working mechanisms [3].
CAD model of ambienBeat and its components
We fabricated an electromagnetic field-driven soft actuator using a customized voice-coil and molded a silicone membrane with a neodymium magnet (Grade N52, 5233 Gauss Disc magnet) embedded, as this does not produce unwanted acoustic noise. We coiled a coated 33 AWG copper wire for 250 turns around a hollow aluminum cylinder (permeability k = 1.46) that had a diameter of 15 mm and height of 50 mm. To fabricate a magnet embedded silicone membrane, we 3D printed a plastic negative dome-shaped mold and a cavity to cast a silicone (EcoFlex 00-30, Smooth On). A barometric MEMS pressure sensor (MPL115A2, NXP) was embedded in the silicone for a touch sensitive pressure sensor. We placed it on the bottom part of the device. It is used for getting feedback of the force produced by the voice-coil soft actuator. We casted Ecoflex 00-50 (Smooth On) in 3D printed molds to make the pressure sensing pad. The main actuation part of the regular size has a diameter of 48 mm and a height of 25 mm. The smaller ambienBeat has a soft actuator with a diameter of 37.9 mm and a height of 15 mm.
Displacement of soft membrane of the noise-less actuator (side view) based on the activation state of the coil
Mechanism of HRV regulation via subliminal tactile biofeedback by ambienBeat
HRV sync. by subliminal tactile feedback by ambienBeat
ambienBeat can be worn in any occasion to regulate your HRV without interrupting the task engagement and not necessarily requiring your control.
Boosting up heart rate; e.g., driving a car
Use-case; boosting HRV during driving
Calming down; e.g., getting stressed due to complex tasks/works
Use-case; for calming down when you got stressed during works
Acoustically noise-less soft actuator driven by electromagnetic field
Displacement of soft membrane by voice-coil actuator
Massachusetts Institute of Technology School of Architecture + Planning
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