應用介電濕潤晶片於微流體圖案化與液體介電泳對於液珠拉伸長度之探討

Using EWOD Device for Microfluidics Patterning and the length of droplet stretched by L-DEP

李相廷(Hsiang-Ting Lee)

指導教授 ： 饒達仁

國立清華大學/工學院/動力機械工程學系/碩士(2019年)

摘要

本論文主要探討介電濕潤(Electrowetting on dielectric, EWOD)晶片應用於微流體圖案化與液珠在不同電壓、電極寬度、電極間距三種參數變化下受到液體介電泳(Liquid dielectrophoresis, L-DEP)的拉伸長度。
本研究藉由平板式EWOD系統與開放式L-DEP系統成功對碳酸丙烯酯液體進行生成、移動、分離和定位，並將碳酸丙烯酯圖案化成不同英文字母，施加電壓範圍分別為140 Vpp/20kHz ~220 Vpp/20kHz與280 Vpp/20kHz，而且在開放式L-DEP系統中將同體積的液體在固定電壓下圖案化成所有的英文字母。由於字母結構不同，圖案化之液珠體積會有所變化，為了更精確控制液珠體積和達成液體介電泳之圖案化，而使用液體介電泳電極探討液珠受液體介電泳力之拉伸長度。
在液體介電泳實驗中，同樣使用碳酸丙烯酯液體當驅動液體，施加電壓為140 Vpp、160 Vpp、200 Vpp，頻率固定20kHz，起因於圖案化的電壓與頻率大多落在此範圍內。晶片分為電極寬度固定為0.1mm和總寬固定為1mm，各別有六組不同電極間距的變化。實驗結果發現兩點，第一點是拉伸長度會隨著電極寬度遞減而下降，第二點是拉伸長度不會隨電極間距增加而改變，當開啟雙電極時，長度會因電極間距增加而漸漸下降。
理論方面是以液珠的受力情形的觀點作分析，主要以電場產生的力、摩擦力與毛細力等等其餘阻力進行力平衡，並從上述實驗結果之觀點改良理論，為了驗證此理論改良結果，便設計三電極晶片進行實驗，並將結果與理論做比較，結果證明理論與三電極晶片實驗結果相符，故可藉此計算出不同電壓、電極寬度、電極間距下受液體介電泳力之液珠拉伸長度與液珠體積大小。
而藉由上述理論與實驗的結果，可得知液體拉伸的長度，鑑於電極寬度和上下板間距皆已知，故可精確得知液珠體積，由液體介電泳電極控制。實驗施加電壓為200 Vpp/20kHz，目前已完成對碳酸丙烯酯液體進行生成、移動、分離和定位，並實現液體介電泳之圖案化。

關鍵字

介電濕潤晶片 ； 微流體圖案化 ； 液體介電泳

並列摘要

This study presents the application of electrowetting on dielectric (EWOD) chip to microfluidic patterning and the length of droplet stretched by liquid dielectrophoresis (L-DEP) under different parameters of voltage, electrode width and electrode spacing.
In this study, by using the parallel plate EWOD system and the open-plate L-DEP system the propylene carbonate liquid was successfully generated, moved, separated and positioned and was patterned into different English alphabets. The range of applied voltage is from 140 Vpp/20 kHz to 220 Vpp/20 kHz and 280 Vpp/20 kHz. Moreover, the same volume of liquid is patterned into all English alphabets at a fixed voltage in the open-plate L-DEP system. Due to the difference in alphabet structure, the volume of droplets to be patterned will change. The L-DEP electrode was applied to investigate the tensile length of the droplet subjected to L-DEP force in order to precisely control the volume of the droplet and achieve L-DEP microfluidics patterning.
The propylene carbonate liquid was also used as the driving liquid in the L-DEP experiment at 140 Vpp/20 kHz, 160 Vpp/20 kHz, 200 Vpp/20 kHz .Because of the voltage required to pattern mostly fall within this range.
The chip is divided into two part.One part is electrode width fixed to 0.1 mm and the other part is total width fixed at 1 mm.Each have a variation of six different electrode spacings. The experimental results showed that the stretching length will decrease as the electrode width decreases.And the stretching length does not change with the increase of the electrode spacing. When the two electrodes are turned on,the length decreases due to an increase in the electrode spacing.
Theoretically, it is analyzed from the viewpoint of the force of the droplet.The force generated by the electric field is balanced with the friction, the capillary force and other resistances. The theory is improved from the viewpoint of the experimental results.In order to verify the theoretical improvement results, a three-electrodes chip was designed for experiments. The results prove that the theory is consistent with the results of the experiment, so that the length of droplet stretched by L-DEP and the volume of droplet can be calculated.
From the results of the theory and experiment described above, the stretching length of the liquid can be known. And since the electrode width and the upper and lower plate spacing are known, the volume of the liquid can be accurately known and controlled by the L-DEP electrode. The applied voltage is 200 Vpp/20 kHz, and the generation, movement, separation and localization of the propylene carbonate liquid have been completed, and the patterning of liquid dielectrophoresis is realized.

並列關鍵字

Electrowetting on Dielectric ； Microfluidics Patterning ； Liquid Dielectrophoresis

參考文獻

[1] R. P. Feynman, "There's plenty of room at the bottom " Journal of microelectromechanical systems, vol. 1, pp. 60-66, 1992.

[2] R. Feynman, "Infinitesimal machinery," Journal of Microelectromechanical Systems, vol. 2, pp. 4-14, 1993.

[3] M. Vallet, B. Berge, and L. Vovelle, "Electrowetting of water and aqueous solutions on poly (ethylene terephthalate) insulating films," Polymer, vol. 37, pp. 2465-2470, 1996.

[4] M. G. Pollack, R. B. Fair, and A. D. Shenderov, "Electrowetting-based actuation of liquid droplets for microfluidic applications," Applied Physics Letters, vol. 77, pp. 1725-1726, 2000.

[5] S. K. Cho, H. Moon, J. Fowler, and C.-J. Kim, "Splitting a liquid droplet for electrowetting-based microfluidics," in Proceedings of 2001 ASME Inter Mech Eng Congress and Expo, November, 2001, pp. 11-16.