A Cost-Effective, High-Performance and Bioinspired Pulse Sensor for Quantitative Assessment of Arterial Stiffness
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In clinical medicine, a wave of blood flow produced by the heartbeat is propagated by the elastic and muscular fibers of the arteries as the wave passes. These waves of pressure can be detected as pulses in arteries close to the skin surface. As the arterial pulse changes when it travels from the central aorta down to the peripheral arteries, therefore, it carries rich physiological and pathological information of the cardiovascular system and the vessels of extremities. Its significance has been identified by the physician as the analysis of arterial pulse characteristics is an integral part of the cardiovascular examination and/or the vessel wall condition assessment. Currently, a number of devices have been investigated toward measuring the pulse waveform more precisely and conveniently. Through the analysis of precisely measured pulse waveforms, it can then help to extract the rich physiological and pathological information.In this thesis, we aim to develop a novel noninvasive and wearable radial pulse sensor that is of high accuracy, low cost, and high sensitivity. To reach the goal, the ultrasensitive hybrid carbon/polymer- basedpiezoresistive (HCP) film with high-sensitivity and low thermal-drift is selected and its miniaturized signal conditioning circuit board is tailor-made. Specifically, inspired by effectively feeling the pulse through the fingertip tactile palpation, by mimicking the fingertip tactile structure featuring with the high-performance mechanical sensing properties such as damping and bandwidth filtering, we design the bioinspired pulse sensor in which the HCP sensing film is enveloped by the skin-like or tissue-like soft rubber. The sensor is well calibrated and its sensing performance including accuracy, repeatability, and sensitivity is experimentally validated. The developed sensor has been employed to measure radial pulses and to further determine arterial stiffness or aging by computing the pulse-related critical vital parameters such as augmentation index (AI) and pulse transit time (PTT). The results indicate the arterial stiffness or aging can be quantitatively assessed by our low-cost but high-performance sensor, which is validated by a commercial sensor.