以高排列性聚(偏氟乙烯-三氟乙烯)微米絲為基礎之柔性壓電血壓計開發

Abstract

本論文主旨是以高靈敏度之可撓式壓電薄膜感測器為基礎，開發可貼附於皮膚之穿戴式血壓計。而為了達到長時間連續生理訊號量測以及可貼附於表皮上，感測器材料必須具有生物相容性與可撓性，而本論文所選用的壓電聚合物，聚(偏氟乙烯-三氟乙烯) P(VDF-TrFE)除了具生物相容性、可撓性之外亦具有良好的化學抗性。 薄膜的製作是利用靜電紡絲製成方法搭配高轉速之滾筒收集器，以製備具有高排列性的壓電微米絲線薄膜，並經過退火、電暈極化等製成提高壓電性質，而由於薄膜是由微米絲線堆疊而成，因薄膜中具有許多孔隙，而這也使得薄膜中同時具有壓電效應與靜電效應。在感測器的製作上，利用平板式電極將電訊號取出，並探討電極幾何、微米絲線方向及彎曲方向對於靈敏度的影響，此外亦探討壓電效應與靜電效應的對於輸出的貢獻，在量化量測上，利用四點彎曲法得出應變與輸出訊號的關係，其結果顯示，在10 mm×10 mm的電極面積下，彎曲方向與絲線方向在平行與垂直的情況下靈敏度具有7.4 到19.3倍的差異，彎曲方向與絲線方向在平行時，壓電效應與靜電效應對靈敏度貢獻分別為68%及32%，而在垂直方向，靜電相對壓電則是-43%的輸出，彎曲方向與絲線方向平行時具有最高的靈敏度，可達到1.06pA/με，另外在2 mm×10 mm電極面積下測試的結果則顯示在電極的長邊與微米絲線平行的情況下，其方向性的比值亦有6.6~12.6倍的差異。 在人體試驗上，除了橈動脈的量測以外，亦比較不同條件下的感測器對於手部運動的抵抗能力，而其結果顯示，在絲線、電極長邊、血管方向三者平行的情況下，具最佳的脈搏波形輸出，且手部運動對於感測器的影響最小，而在不同受試者的量測上，皆可量測到完整的脈搏波形，且感測器之輸出與PPG訊號、血流速訊號皆有相對應的特徵，如心室收縮所造成的波峰、下半身的反射波等，而與PPG訊號的心率比較，差值皆不超過0.09秒。

The purpose of this thesis is to develop a wearable blood pressure device based on a flexible membrane sensor. In order to achieve long-term continuous measurement and attach to the epidermis, the sensor material must be biocompatible and flexible. The piezoelectric polymer P(VDF-TrFE) not only is biocompatible and flexible, it also has an excellent chemical resistance. The piezoelectric membrane was fabricated by electrospinning with a high-speed drum collector, the microfibers can have a high degree of alignment followed by annealing and corona charging process to enhance piezoelectric property. Since the membrane was built by microfibers, there are many void in the membrane. This micro-structure makes the membrane have both piezoelectric and electrostatic effect. In this study, specific surface electrodes are designed for P(VDF-TrFE) membrane and 4-point bending test was used to perform small strain measurement. Experimental results show that using 10 mm by 10 mm surface electrodes, the sensitivity for fibers in parallel with bending was 7.4 to 19.3 higher than the one in perpendicular with bending direction. For the condition of having bending direction and the fibers direction are in parallel, the piezoelectric effect and the electrostatic effect contribute to the sensitivity of 68% and 32%, respectively; while in the condition of vertically aligned, the contribution of electrostatic signal is opposite to piezoelectric signal in -43%. The optimal condition is to align the sensor in parallel with bending direction, the sensitivity can reach 1.06 pA/με. In addition, the results of using 2 mm by 10 mm electrodes show that having fibers align with the bending direction, the ratio of directionality is 6.6(before immerse IPA) and 12.6(after immerse IPA). In human tests, we study the ability of different sensors to minimize the influence of body movement and its sensitivity to arterial-induced skin deformation. Experimental results show that using the sensor with fibers align with blood vessel on the wrist has the highest performance. Furthermore, complete pulse waveforms can be measured among different subjects, and the output of the sensor has characteristics corresponding to the PPG signal and the blood flow signal. The peaks caused by ventricular contraction and the reflected wave of the lower body can also be characterized. The sensor output is also compared to the heart rate of the PPG signal, and the difference is less than 0.09 seconds.