柱狀微結構對液珠熱毛細運動之影響;Effects of microstructures on thermocapillary droplet actuation

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Title:	柱狀微結構對液珠熱毛細運動之影響;Effects of microstructures on thermocapillary droplet actuation
Authors:	謝岱豈;Xie,Dia-qi
Contributors:	機械工程學系
Keywords:	熱毛細力;溫度梯度;表面微結構;thermocapillary force;temperature gradient;microstructure
Date:	2015-12-17
Issue Date:	2016-01-05 19:38:09 (UTC+8)
Publisher:	國立中央大學
Abstract:	近年來微流體技術的快速發展，微流體晶片可對微量流體進行複雜、精確的操作，其具有體積輕巧、使用樣品、試劑量少等優點，因此在生物技術研究上的應用範圍非常廣泛。常見的微流體驅動原理大約可分類為熱毛細力、表面粗糙度梯度、表面化學梯度、靜電力及電濕潤等，和其他方法相較，使用熱毛細力驅動液珠有試片製程簡單、控制容易等優點。由於熱毛細力無法在小範圍內提供極大的液珠驅動力，所以液珠的移動速度並不快，為此在試片上加入柱狀微結構改變液珠在矽晶片上的潤濕性，以期達到增加液珠遷移速度的效果。本論文主要以乾蝕刻在矽表面上製作不同間距的柱狀微結構，並在具有微結構的矽表面上，以熱毛細力驅動液珠，探討微結構對液珠移動的影響。在光滑的矽表面上，發現液珠移動時會產生形變，造成前進角比後退角大，且受溫度梯度越大的液珠移動速度越快；在有微結構的矽表面上，因為微結構造成液珠在固體表面呈現親水性，使熱毛細力變大，所以液珠的位移、速度都比在無結構的表面上快，但由於受到微結構的阻礙，液珠移動時速度不斷下降。最後用牛頓運動定律估算微結構造成的阻力，從固定表面粗糙係數的觀點分析，發現受溫度梯度越大的液珠移動速度越快，受阻力越大；從固定溫度梯度的觀點分析，發現在表面粗糙係數越小的試片上，因試片與液珠接觸的固體面積較少，黏滯摩擦力也較小，液珠的移動速度越快，但受阻力也越大。 ;In recent years, microfluidics technology has been developed rapidly. Microfluidic can be operated complexly and exactly by microfluidic chips. It has many advantages such as lightweight, less reagent, etc. Therefore, the scope of application in biotechnology research is very extensive. Common microfluidic driving principle can be roughly classified into thermocapillary forces, surface roughness gradient, surface chemistry gradient, static electricity and electro-wetting etc. Compared with other methods, using thermocapillary force to drive liquid drop has some advantages like manufacturing process is simple, easy to control and so on. Because thermocapillary force can’t provide great driving force within a small range, the drop moving speed is not fast. To this end, we added column microstructure into silicon wafer to change wettability between squalane droplet and silicon chip, expect to increase the droplet migration speed. This paper, mainly make column microstructure with different spacing on the silicon surface by dry etching, and drive liquid droplet by thermocapillary force on it to investigate the effect of microstructure on the droplet migration. On the smooth silicon surface, droplet will deform when moving. Resulting advancing contact angle is larger than receding contact angle, and the greater the temperature gradient, the droplet moving faster. Because of the microstructure, droplet exhibits hydrophilic on roughness solid surface. Thermocapillary force becomes larger, so the displacement and velocity of droplet is faster than it on smooth surface. But hampered by the microstructure, the moving speed of the droplet is declining. Finally, using Newton′s laws of motion to estimate the resistance caused by micro structure. From a point of the fixed surface roughness coefficient, find that the greater temperature gradient, the faster droplet moves and the greater the resistance. From the view of fixing temperature gradient, find that the smaller the surface roughness coefficient, because the contact area between liquid droplet and solid is fewer, the faster droplet moves, but the greater the resistance.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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