以靜電紡絲研製高排列性壓電薄膜壓力感測器及其指叉式電極之最佳化研究及開發

Abstract

本論文旨在開發高靈敏度之可撓式壓電薄膜感測器，以應用在穿戴式血壓計。為了達到高靈敏度且具可撓性，選用聚(偏氟乙烯-三氟乙烯)(polyvinylidene fluoride/trifluoroethylene， P(VDF-TrFE))高分子壓電材料，並使用滾筒式靜電紡絲製程，製作出具排列性的絲線壓電薄膜，可做為具有可撓性和感測能力的壓力感測器。然而，因為薄膜厚度與絲線間具有孔隙，使用夾層式電極容易短路，因此採用指叉式電極設計，並對不同指叉間距電極之感測薄膜作彎曲訊號測試，另外，本研究亦探討絲線排列方向與指叉方向對靈敏度影響。而為了提升訊號靈敏度，利用X光繞射儀量測薄膜晶相，證明經最佳化退火和電暈極化製程所得薄膜具有較佳之β相晶相，達成壓電性質之製程之最佳化開發。並利用高壓交流電設備量測電滯曲線，證明退火後之薄膜鐵電性質有顯著提升。最後，所得最佳化的指叉設計，量測其彎曲訊號靈敏度15.21 nA/g，所能測定之最小重量為0.1 g，並驗證在2 mm指叉間距時訊號由靜電效應主導，而0.5 mm指叉間距時訊號由壓電效應主導。本研究並應用所開發的絲線壓電薄膜壓力感應器量測到頸動脈之血壓訊號。

The goal of this thesis is to develop a highly sensitive and flexible piezoelectric pressure sensor for the application of wearable blood pressure. To create a high sensitivity and flexibility piezoelectric pressure sensor, the polymer-based piezoelectric P(VDF-TrFE) was chosen in this study. Electrospinning process was applied to electrospun P(VDF-TrFE) into an ultra-flexible thin-film like structure. Using electrospinning process with a rotating drum collector, fibers with different levels of alignment are created and studied. In order to enhance the sensitivity and prevent shortage between electrodes, inter-digitated electrodes (IDEs) were developed. Design parameters include gaps distance between electrodes, and orientations between IDEs and the direction of fiber alignments. Furthermore, the β crystal phase of P(VDF-TrFE) is optimized by studying its X-ray Diffraction (XRD) patterns under the conditions of annealing and corona discharge poling processes. It was found that the β phase can be enhanced and the sensitivity can be much improved by 1.92 ~ 5.84 times. Measurements of P-E curves are also conducted to verified the experimental findings. The maximum sensitivity was 15.21 nA/g by using bending test, and the lightest weight that can be measured is 0.1 g. Finally, it is verified that the developed thin-film piezoelectric pressure sensor can be used to measure the blood pressure signal on the skin near the carotid artery.