A fingertip-type magnetic pulse detection device for unusual monitoring conditions

Abstract

Wearable devices for continuous non-invasive monitoring of physiological signals are crucial for preventive care and management of chronic conditions. However, these devices are either sensitive to skin conditions or require external stimuli, such as light or electrical excitation, to penetrate the skin for pulse detection. This often results in large motion artifacts and unsuitability for certain skin conditions. Here we demonstrate a simple fingertip-type device which can detect clear pulse signals under a range of conditions, including fingers covered by opaque substances such as a plaster or nail polish, or fingers immersed in water. The structure of the device consists of a pair of magnets and a magnetic sensor. Both experimental and numerical results show that the detected pulsation signals correspond directly to the vibrations induced by blood circulation with negligible influence from modulated magnetic signature of blood. Therefore, this device could be used in conditions which are challenging for existing pulse detectors and might also have its application extended to blood pressure measurement.

The effect of contact pressure on photoplethysmography

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“…Recording the intensity of reflected and transmitted light through the measured location, pulse wave signals could be obtained, which consists of arterial pulses period of each heartbeat, and plenty of biometric information can be detected [2]. The most typical application of PPG monitoring is transmission-mode finger pulse oximetry [3], whereas reflected PPG acquisition positions are more adaptable for wearable devices [4]. In recent years, research interest in PPG applications has grown beyond oximetry to encompass diabetes, hypertension, atherosclerosis, coronary artery disease, coronary heart disease, heart rate, and blood pressure monitoring [5].…”