利用熱毛細作用與熱對流現象控制水液珠 在矽油表面上的移動行為分析;Analysis of water droplet migration on silicone oil surface controlled by thermocapillary and heat convection

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题名:	利用熱毛細作用與熱對流現象控制水液珠在矽油表面上的移動行為分析;Analysis of water droplet migration on silicone oil surface controlled by thermocapillary and heat convection
作者:	鄧智仁;Teng, Chih-Jen
贡献者:	機械工程學系
关键词:	熱毛細力;控制液珠
日期:	2019-08-26
上传时间:	2019-09-03 16:42:28 (UTC+8)
出版者:	國立中央大學
摘要:	近年來微流體技術蓬勃發展，微流體晶片可對微小流體進行複雜且精確的操作，其具有體積小、消耗試劑量少等優點，因此在生物醫學技術相關領域研究上的應用範圍非常廣泛。常見的驅動液珠移動原理大約可分類為熱毛細力、表面結構梯度、靜電力及電濕潤等，相較於其他方法，使用熱毛細力驅動液珠有試片製程簡單、控制容易等優勢。熱毛細力驅動液珠通常以固體表面為基底，可能會有液珠滯留、汙染基板、液珠揮發以及不可逆等缺點。本文使用與水不互溶之矽油做為液體平台，利用熱毛細現象以及熱對流來控制水液珠移動，加熱矽油時，矽油內部產生熱毛細現象使冷端液面上升，熱端液面下降而使矽油表面產生高低落差而傾斜，將液珠滴於冷端時會往溫度較高的方向移動。而當矽油液面高度於一定高度時，因矽油內部之熱對流現象大於熱毛細現象，則會使液珠由熱端往冷端移動。本研究以此方法呈現兩種不同的液珠移動方向。　　本文以底部加熱的方式提供穩定的溫度梯度，探討不同液面高度、不同溫度梯度與不同液珠大小對於液珠移動的影響。在原始液面高度2 mm，溫度梯度為0.326℃/mm時，6μL液珠移動速度達到8.07 mm/s。由實驗得知不同溫度梯度與原始液面高度對於液面高低變化差值的影響並不明顯；由PIV實驗得知當固定溫度梯度時，原始液面高度越高則矽油流速越快，固定原始液面高度時，溫度梯度越大則矽油流速越快。因此在液面加熱後高低落差接近的情況下，液珠移動行為主要受到熱對流現象之矽油表面流動所影響。 ;In recent years, droplet-based microfluidic systems have been popular topics. There are lots of application of droplet manipulation in several industries, such as chemical and biology. Different methods of actuating droplets are available now, for example, electrostatic, surface structural gradient, and thermocapillary. Thermocapillary method is easier to control and cost lower energy. Traditional thermocapillary method is usually based on droplet lay on solid substrate. But there may be some disadvantages like droplet pinning, droplet evaporation, substrate contamination and irreversibility. To overcome the shortcomings of traditional liquid-solid thermalcapillary method, we use silicone oil as platform and DI water droplets to demonstrate a liquid-liquid manipulation. In this research, we partially heat up silicone oil platform in a copper based container by heater at the bottom and partially cool down by a cooler at the other side to provide temperature gradients. When silicone oil around heater is heated, the surface tension will decrease and then pulled to the colder side. So the surface profile of silicon oil platform is like a ramp. Droplets will move from the cold side to hot side. We apply different temperature gradients, silicone oil surface height and different droplet sizes to determine their relationship. When the silicone oil surface height achieve a specific value, the effect of heat convection of the silicone oil will overcome the gravity force caused by thermocapillary effect and then drag the droplets to migrate from hot side to cold side. We get the largest droplet velocity 8.07 mm/s at 2 mm surface height with 0.326℃/mm of temperature gradient and droplet size of 6 μL.
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