Triboelectric sensor for pulse wave monitoring
Kanko, Natalia (2023)
2023
Sähkötekniikan DI-ohjelma - Master's Programme in Electrical Engineering
Informaatioteknologian ja viestinnän tiedekunta - Faculty of Information Technology and Communication Sciences
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Hyväksymispäivämäärä
2023-05-17
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202305115686
https://urn.fi/URN:NBN:fi:tuni-202305115686
Tiivistelmä
The pulse wave measured in the peripheral circulatory provides clinically valuable information on the condition of the cardiovascular system. Heart rate, elasticity of arteries, blood pressure variations in the systolic and diastolic phases and vascular resistance are all reflected in the shape and velocity of the pulse wave. The pulse wave can be measured above the radial artery using a self-powered thin-film sensor that converts the weak pressure variations from the skin surface into an electrical signal, providing a non-invasive and energy-efficient approach to pulse wave monitoring. Among these self-powered sensors proposed in the literature, triboelectric sensors are one promising solution.
This thesis focuses on evaluating triboelectric sensors and their applicability in pulse wave measurements. Specifically, a triboelectric sensor based on a material approach that utilizes expandable microspheres is evaluated. The design, fabrication, and characterization of the sensor are described, including its five-layer structure. The central component of the sensor is expandable microspheres, which mixed with elastic PDMS, results a pressure-sensitive layer that exhibits high deformation at low pressure. The sensitivity of the sensor is determined by electromechanical measurements, and its performance is evaluated against a reference sensor in pulse wave measurement. The measured signals are analyzed both visually and numerically to gain a better understanding of the sensor suitability for quantitative assessment of arterial conditions.
The results of the sensor fabrication demonstrated how time and rotational speed affected the layer thickness in the spin-coating process of the PDMS-microsphere mixture. Additionally, the effect of temperature on the expansion of microspheres was demonstrated. The results of electrical characterization showed that the sensor is capable of self-powered measurement of the pulse wave from the wrist above the radial artery. Based on electromechanical measurements, the maximum sensitivity of the sensor was defined as 1.4 pC/N. However, these measurements exhibited a significant amount of variation. The pulse wave measurement produced a signal with visually detectable pulse wave features. These features were also detectable by an automated analysis. A quantitative comparison with a reference sensor showed that the triboelectric sensor has the potential to assess physiological parameters such as heart rate or arterial stiffness.
This thesis focuses on evaluating triboelectric sensors and their applicability in pulse wave measurements. Specifically, a triboelectric sensor based on a material approach that utilizes expandable microspheres is evaluated. The design, fabrication, and characterization of the sensor are described, including its five-layer structure. The central component of the sensor is expandable microspheres, which mixed with elastic PDMS, results a pressure-sensitive layer that exhibits high deformation at low pressure. The sensitivity of the sensor is determined by electromechanical measurements, and its performance is evaluated against a reference sensor in pulse wave measurement. The measured signals are analyzed both visually and numerically to gain a better understanding of the sensor suitability for quantitative assessment of arterial conditions.
The results of the sensor fabrication demonstrated how time and rotational speed affected the layer thickness in the spin-coating process of the PDMS-microsphere mixture. Additionally, the effect of temperature on the expansion of microspheres was demonstrated. The results of electrical characterization showed that the sensor is capable of self-powered measurement of the pulse wave from the wrist above the radial artery. Based on electromechanical measurements, the maximum sensitivity of the sensor was defined as 1.4 pC/N. However, these measurements exhibited a significant amount of variation. The pulse wave measurement produced a signal with visually detectable pulse wave features. These features were also detectable by an automated analysis. A quantitative comparison with a reference sensor showed that the triboelectric sensor has the potential to assess physiological parameters such as heart rate or arterial stiffness.