電濕潤微黏滯計之研發

Abstract

在目前的生醫檢測上，所要求待測物的量越來越少，而檢測儀器也相對需要微型化的設計。傳統黏滯計的設計，大部份是利用機械力或是電磁力的方式驅動流體，而在這篇研究裡，所設計的微型化黏滯計則以Electrowetting on Dielectric (EWOD)的方法，施加電場改變流體與流道間的表面張力使液體流動，並利用液體在微流道裡的速度梯度，可以量測約10 μl溶液的黏滯係數。 我們設計兩種不同的晶片，晶片面積均為2.3 cm × 2.3 cm，分別為直線形與弧形的流道，各有四種不同大小的電極和三種不同寬度的流道，以標準的微機電製程製作晶片，量取不同的流速梯度套入公式中求得黏滯係數。EWOD中的介電層是一種高介電係數的材料—BST (Ba0.7Sr0.3TiO3)，可以降低所需要供給的電壓，其介電係數範圍從120到200，並在表面塗佈一層斥水性的聚合物—鐵氟龍。從數值的模擬模擬結果，外加20伏特電壓，可以量測溶液的流速範圍是5 ~ 140 mm/sec，而黏滯係數範圍為0.5×10-3 ~ 2×10-3 Pa-s。實驗結果則是以生理食鹽水在直線形的流道中施加15伏特的電壓，得到的流速0.3167~0.66 mm/s以及粘滯係數40.26 Pa-s。

Nowadays, the bio- medical analysis requires fewer amount of sample, and the analysis device should be scaled down as well. The traditional viscometers utilize mechanical forces from the motors and electro- magnetic forces in the channel mostly. However, in this study, the micro viscometer uses Electrowetting on Dielectric (EWOD) to change the surface tension between liquid and channel and uses liquid velocity gradient in the channel to find the viscosity coefficient with the volume of 10 μl. In this paper, we use electrowetting on dielectric (EWOD) to drive the liquids. There are four different sizes of electrode on a 2.3 cm× 2.3 cm chip, and two kinds of channel to measure the velocity gradient for the viscosity coefficient. The device is fabricated by means of micro electro mechanic system (MEMS) technology. The dielectric layer of EWOD is a high dielectric constant material — BST (Ba0.7Sr0.3TiO3), which ranges from 120 to 200 therefore reducing the required applied voltage, with hydrophobic polymer (Teflon® AF) coated on surface. Our simulation results indicate the feasibility of this device for various solutions with viscosity coefficient in the range of 0.5×10-3 ~ 2×10-3 Pa-s, which corresponds to the velocity ranging from 5 to 140 mm/sec by applying 20 volts to the devices. The experiment results show that saline can be pulled in linear channels by applying a voltage of 15 volts with a velocity 0.3167~0.66 mm/s and viscosity coefficient 40.26 Pa-s.