具微針結構電容式流量感測器應用於器官晶片微流道系統

Abstract

本研究開發高靈敏度的微型壓力感測器，並將其整合於器官晶片微流道系統以應用於非侵入式且即時量測微流道的流量變化。感測器包含上方浮動式電極與下方電極對，中間之介電層則是採用聚二甲基矽氧烷(Polydimethylsiloxane, PDMS)之微結構薄膜。浮動式電極的設計可以有效減少電容感測器接線上的困難度，使感測器更容易整合於微流道系統。加入PDMS微結構薄膜可以使電容感測器擁有高靈敏度、廣大的量測區間、更線性的電容變化程度與降低遲滯現象等優勢。此外，本研究亦利用Ansys Fluent商用軟體進行流體模擬，分析微流道之流體在層流情況下之運動狀態。因為微流道內流量的改變會造成流道腔體內壓力的變化，因此可以藉由偵測流道內壓力的變化來預估流量。此微流道流量感測器在0~900μl/min的流量範圍內擁有良好的且線性的電容變化。同時在浮動電極結構厚度為100μm時，微流道流量感測器有最佳的靈敏度0.0207%．min/μL。

This work presents the design and fabrication of a highly-sensitive miniaturized pressure sensor that can be integrated with an organ-on-chip system for nonintrusive and rapid monitoring of flow rate in microfluidic channels. The proposed device employs a variable capacitor for pressure sensing. The capacitor consists of a sensing electrode pair, a common floating electrode, and a microstructured PDMS dielectric layer sandwiched between the electrodes. The design with the floating electrode can effectively reduce the complexity of the device interconnects for retrieving signals. The microstructured thin film gives advantages such as wide sensing range, low hysteresis, and good linearity. Three dimensional Navier–Stokes simulations is carried out by a Finite Volume Method (FVM) solver in a laminar flow condition in order to investigate the behavior of the fluid in the channel. The pressure in the microfluidic channel can deform the PDMS membrane on the top of the floating electrode, which in turn changes the gap of the capacitance and thus changes the capacitance. Therefore, the pressure change can be detected by measuring the capacitance change. The sensor has the linear response in the range of 0~900μl/min for the optimal sensor performance. The highest sensitivity is about 0.0207%．min/μL for the membrane with a thickness of 100μm.