電熱效應於石英晶體微天平及微混合器之研究

Study on a Biosensor and a Micromixer Utilizing Electrothermal Effect

黃耀弘(Yao-Hung Huang)

指導教授 ： 黃榮山 ； 張正憲

國立臺灣大學/工學院/應用力學研究所/博士(2015年)

https://doi.org/10.6342/NTU.2015.02476

摘要

在微流體感測晶片中，樣品的檢測因受限於擴散作用，造成檢測時間過長。電熱效應可驅動微流體，增加待測生物分子與感測面上捕捉分子的接觸機會進而增加結合量。本研究將電熱效應用之微電極與石英晶體微天平整合，生物分子透過電熱效應驅動可快速抵達感測面。在施加交流電壓10Vpp10M Hz作用下，電熱效應形成渦旋的最高流速為383μm/s。待測分子以微流道方式導入後，將流體切換為靜態後的第10~15分鐘期間，開啟電熱效應持續5分鐘，所造成的生物分子附加質量負載，可即時在液態下量測共振頻率的偏移量。本研究使用直徑20nm和1μm的氨基乳膠粒子進行實驗，在開啟電熱效應作用期間，20nm氨基乳膠粒子在濃度1013和1014 spheres/mL的共振頻率變化量分別為24.6 ± 4.9Hz和53.2 ± 10.6 Hz，而無電熱效應的控制組分別為2.7 ± 0.5 Hz 和18.1± 3.6 Hz。1μm氨基乳膠粒子在濃度108和109 spheres/mL的共振頻率變化量分別為15.6± 2.3Hz和33.1± 8.3Hz，而無電熱效應的控制組分別為2.2 ± 1.2Hz 和13.1±2.6 Hz。由掃瞄式電子顯微鏡驗證實驗結果，證明電熱效應可增加生物分子的結合量，提供微流體感測晶片一快速檢測方法。
此外，在微奈米結構的生化應用上，常需快速混合兩種流體。一般混合器常使用機械式攪拌以加速混合。然而在微奈米尺度下，機械式攪拌難以置入，自然擴散乃混合的主要機制。但若僅靠自然擴散，將需要很長的微混合器流道。本研究將電熱效應應用在微混合器上，藉用電熱效應的作用下，混合效率在體積流率20μl/hr、50μl/hr和100μl/hr分別為93.6%、88.4% 和 80.7 %, 而無電熱效應的控制組分別 57.3%、23.5%和21.7 %。證明電熱效應可有效加速微流道內兩流體的混合。

關鍵字

電熱效應 ； 石英晶體微天平 ； 微混和器 ； 結合效率

並列摘要

In this work, a conventional commercial quartz crystal microbalance (QCM) with a reaction chamber modified by integrating into our designed multi-microelectrodes to produce electrothermal vortex flow is used to perform a series of frequency shift measurements due to the adding mass coming from the specific binding of the analytes in the fluid flow and the immobilized ligands on the QCM sensing surface. In a diffusion-limited sensing process, it often takes a long time to complete a detection due to the slow motion of analytes. Electrothermal vortex flow can efficiently drive the analyte movement in the fluid toward the sensing surface and accelerate the detection with the additional advantages of small amount analytes, acceptable local temperature rise, and negligible pressure loss of the fluid flow. In the experiments, the analytes carried in the PBS buffer solution is firstly guided to flow through the micro-channel to displace the solution in the flow cell completely. In the beginning, the binding of analyte and ligand proceeds due to pure diffusion of analytes to the binding surface of the QCM sensor. After about 10-15 min, the binding rate is observed to a near quasi-static state. At this moment, to avoid the mutual interference of electric fields produced by QCM electrodes and electrothermal microelectrodes, we first cease the QCM frequency sensing by removing the applied alternating voltage and then add the driving voltage to the multi-microelectrodes to activate the electrothermal vortex flow for about 5 min. Then we shut down ETE and start QCM sensing again. As control groups, blank experiments without applying electrothermal effect (ETE) are also done for the purpose of comparisons. Amine latex beads as analytes (diameter, 20nm and 1μm) were used in the experiments. Cysteamines as ligands are pre-self-assembled on the gold-coated QCM surface. In the case of 20-nm amine latex beads in ETE phase, the resonant frequency variations at concentrations of 1013 and 1014 spheres/mL were 24.6 ± 4.9 and 53.2 ± 10.6 Hz, respectively. In the control group without ETE, the respective variations were 2.7 ± 0.5 Hz and 18.1± 3.6 Hz, respectively. In the case of 1-μm amine latex beads with ETE, the resonant frequency variations at concentrations of 108 and 109 spheres/mL were 15.6± 2.3 and 33.1± 8.3 Hz, respectively, while those in the control group without ETE were 2.2 ± 1.2 Hz and 13.1±2.6 Hz, respectively. In addition, the images of the binding surfaces with or without applying ETE are taken through the scanning electron microscopy (SEM). Comparing the images, it clearly indicates that ETE does raise the specific binding of the analytes and ligands and efficiently improve the performance the QCM sensor.
In addition, biochemical applications often require rapid mixing of different fluid samples. At the microscale level, the fluid flow is usually highly ordered laminar flow and the lack of turbulence makes the diffusion be the primary mechanism for mixing. The electrothermal effect can be generated to induce disturbance to the flow field and hence promote the mixing efficiency for the micromixer. In ETE phase, the mixing indexes within 2000μm mixing length at flow rate of 20, 50 and 100 μl/hr were 93.6%, 88.4% and 80.7 %, respectively. In the control group without ETE, the mixing indexes were 57.3%, 23.5% and 21.7 %, respectively.

並列關鍵字

electrothermal effect ； quartz crystal microbalance ； micromixer ； binding efficiency

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