以水平振動驅動數位液滴於傾斜平板移動與爬升之影響參數與運動機制探討

Abstract

本研究探討液滴於固體表面上受水平振動驅動後運動之現象，並針對驅動波形進行改進，使其具有更好的驅動效率，首次成功完成以水平振動驅動液滴於傾斜平面上之爬升。本研究主要可分為三部分，第一部分為液滴於水平基板上長程運動之力學表現分析，第二部分為波形改進及親疏水性對液滴在水平基板移動產生之影響，第三部分為液滴於傾斜基板上爬升現象之探討。 本研究於第一部分中發現了數位液滴操控啟動過程中，會出現速度差上3倍以上的兩段式速度區：運動開始時的固定速度，而在經過一個液滴直徑後，則進入一個快的定速度區。此現象為首次發現，另外也發現液滴在基板上運動的過程中會受到表面是否潤濕所影響，而後也進行定量分析基板之運動指標參數比較，探討水平振動平板上之液滴運動行為與形成快區與慢區差異機制，而後發現疏水表面有加強液滴移動的效果。 第二部分則為更改驅動波形對液滴運動速度之影響。本研究以前人使用之波形(Waveform A)作為對照，本研究在驅動波形中加入了靜程的停歇即為Waveform B，從兩者驅動液滴的結果差異，可以表現此改變有較好的液滴移動效率，與較大的液滴移動視窗。 第三部分中，吾人使用新設計的驅動波形，以水平振動方式驅動，首次成功將液滴順利爬升傾斜45度之基板，並繪製出其控制參數的相圖。

This research investigates the phenomenon of sessile drop motion on solid surface driven by horizontal vibration, and improves the driving waveform to make it more efficient and further successfully drive the droplet climbing on inclined plane by horizontal vibration for the first time. This research can be divided into three parts. First part is the long-range motion of digital droplets driven by horizontal vibration on a horizontal substrate. Second, the effect of waveform improvement on droplet movement has been discussed. The last part is the investigation of the phenomenon of droplet climbing on an inclined substrate driven by horizontal vibration. Two velocity zones that velocity can differ at least 3 times between the zones are found in the long-range motion of droplets in the first part of this study. The uniform but lower velocity happened at the beginning of the motion, and then becomes faster. This phenomenon has never been reported in the literature and is a new finding of droplet motion driven by vibration. It is also found that the droplet movement on the substrate is significantly influenced by whether the surface is wetted or not. The mechanism of droplet motion on the horizontally vibrating plate was then investigated by quantitatively analyzing the parameters of the substrate and droplet motion, further discussed the moving mechanism of liquid droplet and the difference of formation of fast and slow zone. Then, the increase of droplet velocity on the horizontally vibrating substrate were observed by making the substrate more hydrophobicity. The second part is the effect of changing the driving waveform on the droplet motion speed. In this study, the previous waveform (Waveform A) was used as comparison. For improved waveform, the working period was reduced and a pause period was added to the triangular waveform to make it Waveform B. The difference in the droplet driving results between the two waveforms was compared. From the comparison results, we can observe that Waveform B has better droplet movement efficiency and larger droplet movement window compared to Waveform A. Also, it is found that the acceleration value of the substrate has a significant effect on the droplet movement speed. Based on the first and second part, we introduced the tilt angle of the substrate to our experiment and used Waveform B to drive the inclined substrate by horizontal vibration, resulting in climbing phenomenon of the droplets. The motion of the droplet at different frequencies and tilt angles can be seen that the droplet moves differently at different frequencies, in the order of stationary, slow climbing, fast climbing, slow climbing, stationary and sliding down from lower to higher frequency, and the larger the inclination angle, the smaller the droplet climbing window and the slower the climbing speed.