應用於連續血壓量測之高靈敏度壓力感測器的開發

Abstract

本研究開發一創新壓力感測器，並將其應用於以動脈張力法為理論基礎之侵入式連續血壓量測系統。動脈張力法之量測血壓的方式為在手腕橈動脈上方放置壓力感測裝置，並施加一固定外力於其上直到血管壁上方因外力扁平。由於壓力感測器所量測之動脈壓會與連續血壓值呈正相關，經由後端訊號處理演算即可得到連續血壓值資訊。本研究之高靈敏度壓力感測器之基礎材料為多壁奈米碳管與PDMS聚合物混合之導電高分子。製程中利用尼龍濾膜作為模具，在導電高分子薄膜表面上轉印出眾多微圓頂結構，並且結合兩導電高分子薄膜以形成互鎖式微圓頂結構。當ㄧ外部壓力施加於感測器上時，兩個接觸微圓頂結構面之間的接觸面積會急遽增加，並且顯著地減少穿隧電阻，因而讓此類型的穿隧壓阻感測元件比一般利用滲透理論的導電高分子材料之壓阻元件還要靈敏許多。除此之外，因為立即壓力變化所產生的互鎖式微圓頂結構表面變形所引起的接觸面積劇烈變化，讓此互鎖式微圓頂結構具有非常快速的動態反應。 根據實驗結果，本研究之量測血壓裝置可即時偵測到動態的脈壓變化。且脈搏波形內之特徵點參數經後段訊號處理及分析後皆符合受測者年齡，證實為一可靠之脈壓訊號。在未來的研究中，將可以利用此動脈壓力訊號轉換成連續動態血壓資訊並且提供給學術研究及臨床醫學上使用。

In this work, we developed the prototype of a non-invasive continuous blood pressure monitoring system based on tonometric measurement by employing a novel highly sensitive pressure sensor. According to the tonometric measurement method, the sensor device is placed on the skin above a radial artery against a bone by a normal force, and induces a local occlusion of artery. Then, the sensor measured the arterial pressure which is directly proportional to the blood pressure. The proposed highly sensitive pressure sensor comprises multiwall carbon nanotubes and polydimethylsiloxane polymer. A nylon membrane filter is proposed to serve as a mold for numerous microdome patterns, which were transferred onto a conductive polymer film. The proposed device features advantages such as ultra-high sensitivity, flexibility, and a simple fabrication process. When external pressure is applied, the contact area between the two contacting microdome structures increases sharply, thereby considerably reducing the tunneling resistance. Such tunneling piezoresistive devices are much more sensitive than those composed of typical conductive polymer materials, whose conductivities are governed by the percolation theory. Experimental results show continuous pulse signals at the radial artery can be tracked by the pressure sensing device. The parameters of the pulse waveforms were also resolved by the device. By using the Fast Fourier Transformation (FFT) technique, the drift and high-frequency noise were successfully filtered out. Potentially the measured pulse pressures can be transformed into dynamic blood pressure signals in the future.